p2p/discv5: added new topic discovery package

26 files changed, 7906 insertions, 0 deletions

diff --git a/p2p/discv5/crypto.go b/p2p/discv5/crypto.go
new file mode 100644
index 000000000..f68d03908
--- /dev/null
+++ b/p2p/discv5/crypto.go
@@ -0,0 +1,31 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	//"github.com/btcsuite/btcd/btcec"
+	"github.com/ethereum/go-ethereum/crypto/secp256k1"
+)
+
+func S256() *secp256k1.BitCurve {
+	return secp256k1.S256()
+}
+
+// This version should be used for NaCl compilation
+/*func S256() *btcec.KoblitzCurve {
+	return S256()
+}*/
diff --git a/p2p/discv5/database.go b/p2p/discv5/database.go
new file mode 100644
index 000000000..7c47c27fd
--- /dev/null
+++ b/p2p/discv5/database.go
@@ -0,0 +1,413 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Contains the node database, storing previously seen nodes and any collected
+// metadata about them for QoS purposes.
+
+package discv5
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/binary"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+var (
+	nodeDBNilNodeID      = NodeID{}       // Special node ID to use as a nil element.
+	nodeDBNodeExpiration = 24 * time.Hour // Time after which an unseen node should be dropped.
+	nodeDBCleanupCycle   = time.Hour      // Time period for running the expiration task.
+)
+
+// nodeDB stores all nodes we know about.
+type nodeDB struct {
+	lvl    *leveldb.DB   // Interface to the database itself
+	self   NodeID        // Own node id to prevent adding it into the database
+	runner sync.Once     // Ensures we can start at most one expirer
+	quit   chan struct{} // Channel to signal the expiring thread to stop
+}
+
+// Schema layout for the node database
+var (
+	nodeDBVersionKey = []byte("version") // Version of the database to flush if changes
+	nodeDBItemPrefix = []byte("n:")      // Identifier to prefix node entries with
+
+	nodeDBDiscoverRoot          = ":discover"
+	nodeDBDiscoverPing          = nodeDBDiscoverRoot + ":lastping"
+	nodeDBDiscoverPong          = nodeDBDiscoverRoot + ":lastpong"
+	nodeDBDiscoverFindFails     = nodeDBDiscoverRoot + ":findfail"
+	nodeDBDiscoverLocalEndpoint = nodeDBDiscoverRoot + ":localendpoint"
+	nodeDBTopicRegTickets       = ":tickets"
+)
+
+// newNodeDB creates a new node database for storing and retrieving infos about
+// known peers in the network. If no path is given, an in-memory, temporary
+// database is constructed.
+func newNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
+	if path == "" {
+		return newMemoryNodeDB(self)
+	}
+	return newPersistentNodeDB(path, version, self)
+}
+
+// newMemoryNodeDB creates a new in-memory node database without a persistent
+// backend.
+func newMemoryNodeDB(self NodeID) (*nodeDB, error) {
+	db, err := leveldb.Open(storage.NewMemStorage(), nil)
+	if err != nil {
+		return nil, err
+	}
+	return &nodeDB{
+		lvl:  db,
+		self: self,
+		quit: make(chan struct{}),
+	}, nil
+}
+
+// newPersistentNodeDB creates/opens a leveldb backed persistent node database,
+// also flushing its contents in case of a version mismatch.
+func newPersistentNodeDB(path string, version int, self NodeID) (*nodeDB, error) {
+	opts := &opt.Options{OpenFilesCacheCapacity: 5}
+	db, err := leveldb.OpenFile(path, opts)
+	if _, iscorrupted := err.(*errors.ErrCorrupted); iscorrupted {
+		db, err = leveldb.RecoverFile(path, nil)
+	}
+	if err != nil {
+		return nil, err
+	}
+	// The nodes contained in the cache correspond to a certain protocol version.
+	// Flush all nodes if the version doesn't match.
+	currentVer := make([]byte, binary.MaxVarintLen64)
+	currentVer = currentVer[:binary.PutVarint(currentVer, int64(version))]
+
+	blob, err := db.Get(nodeDBVersionKey, nil)
+	switch err {
+	case leveldb.ErrNotFound:
+		// Version not found (i.e. empty cache), insert it
+		if err := db.Put(nodeDBVersionKey, currentVer, nil); err != nil {
+			db.Close()
+			return nil, err
+		}
+
+	case nil:
+		// Version present, flush if different
+		if !bytes.Equal(blob, currentVer) {
+			db.Close()
+			if err = os.RemoveAll(path); err != nil {
+				return nil, err
+			}
+			return newPersistentNodeDB(path, version, self)
+		}
+	}
+	return &nodeDB{
+		lvl:  db,
+		self: self,
+		quit: make(chan struct{}),
+	}, nil
+}
+
+// makeKey generates the leveldb key-blob from a node id and its particular
+// field of interest.
+func makeKey(id NodeID, field string) []byte {
+	if bytes.Equal(id[:], nodeDBNilNodeID[:]) {
+		return []byte(field)
+	}
+	return append(nodeDBItemPrefix, append(id[:], field...)...)
+}
+
+// splitKey tries to split a database key into a node id and a field part.
+func splitKey(key []byte) (id NodeID, field string) {
+	// If the key is not of a node, return it plainly
+	if !bytes.HasPrefix(key, nodeDBItemPrefix) {
+		return NodeID{}, string(key)
+	}
+	// Otherwise split the id and field
+	item := key[len(nodeDBItemPrefix):]
+	copy(id[:], item[:len(id)])
+	field = string(item[len(id):])
+
+	return id, field
+}
+
+// fetchInt64 retrieves an integer instance associated with a particular
+// database key.
+func (db *nodeDB) fetchInt64(key []byte) int64 {
+	blob, err := db.lvl.Get(key, nil)
+	if err != nil {
+		return 0
+	}
+	val, read := binary.Varint(blob)
+	if read <= 0 {
+		return 0
+	}
+	return val
+}
+
+// storeInt64 update a specific database entry to the current time instance as a
+// unix timestamp.
+func (db *nodeDB) storeInt64(key []byte, n int64) error {
+	blob := make([]byte, binary.MaxVarintLen64)
+	blob = blob[:binary.PutVarint(blob, n)]
+	return db.lvl.Put(key, blob, nil)
+}
+
+func (db *nodeDB) storeRLP(key []byte, val interface{}) error {
+	blob, err := rlp.EncodeToBytes(val)
+	if err != nil {
+		return err
+	}
+	return db.lvl.Put(key, blob, nil)
+}
+
+func (db *nodeDB) fetchRLP(key []byte, val interface{}) error {
+	blob, err := db.lvl.Get(key, nil)
+	if err != nil {
+		return err
+	}
+	err = rlp.DecodeBytes(blob, val)
+	if err != nil {
+		glog.V(logger.Warn).Infof("key %x (%T) %v", key, val, err)
+	}
+	return err
+}
+
+// node retrieves a node with a given id from the database.
+func (db *nodeDB) node(id NodeID) *Node {
+	var node Node
+	if err := db.fetchRLP(makeKey(id, nodeDBDiscoverRoot), &node); err != nil {
+		return nil
+	}
+	node.sha = crypto.Keccak256Hash(node.ID[:])
+	return &node
+}
+
+// updateNode inserts - potentially overwriting - a node into the peer database.
+func (db *nodeDB) updateNode(node *Node) error {
+	return db.storeRLP(makeKey(node.ID, nodeDBDiscoverRoot), node)
+}
+
+// deleteNode deletes all information/keys associated with a node.
+func (db *nodeDB) deleteNode(id NodeID) error {
+	deleter := db.lvl.NewIterator(util.BytesPrefix(makeKey(id, "")), nil)
+	for deleter.Next() {
+		if err := db.lvl.Delete(deleter.Key(), nil); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// ensureExpirer is a small helper method ensuring that the data expiration
+// mechanism is running. If the expiration goroutine is already running, this
+// method simply returns.
+//
+// The goal is to start the data evacuation only after the network successfully
+// bootstrapped itself (to prevent dumping potentially useful seed nodes). Since
+// it would require significant overhead to exactly trace the first successful
+// convergence, it's simpler to "ensure" the correct state when an appropriate
+// condition occurs (i.e. a successful bonding), and discard further events.
+func (db *nodeDB) ensureExpirer() {
+	db.runner.Do(func() { go db.expirer() })
+}
+
+// expirer should be started in a go routine, and is responsible for looping ad
+// infinitum and dropping stale data from the database.
+func (db *nodeDB) expirer() {
+	tick := time.Tick(nodeDBCleanupCycle)
+	for {
+		select {
+		case <-tick:
+			if err := db.expireNodes(); err != nil {
+				glog.V(logger.Error).Infof("Failed to expire nodedb items: %v", err)
+			}
+
+		case <-db.quit:
+			return
+		}
+	}
+}
+
+// expireNodes iterates over the database and deletes all nodes that have not
+// been seen (i.e. received a pong from) for some allotted time.
+func (db *nodeDB) expireNodes() error {
+	threshold := time.Now().Add(-nodeDBNodeExpiration)
+
+	// Find discovered nodes that are older than the allowance
+	it := db.lvl.NewIterator(nil, nil)
+	defer it.Release()
+
+	for it.Next() {
+		// Skip the item if not a discovery node
+		id, field := splitKey(it.Key())
+		if field != nodeDBDiscoverRoot {
+			continue
+		}
+		// Skip the node if not expired yet (and not self)
+		if bytes.Compare(id[:], db.self[:]) != 0 {
+			if seen := db.lastPong(id); seen.After(threshold) {
+				continue
+			}
+		}
+		// Otherwise delete all associated information
+		db.deleteNode(id)
+	}
+	return nil
+}
+
+// lastPing retrieves the time of the last ping packet send to a remote node,
+// requesting binding.
+func (db *nodeDB) lastPing(id NodeID) time.Time {
+	return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPing)), 0)
+}
+
+// updateLastPing updates the last time we tried contacting a remote node.
+func (db *nodeDB) updateLastPing(id NodeID, instance time.Time) error {
+	return db.storeInt64(makeKey(id, nodeDBDiscoverPing), instance.Unix())
+}
+
+// lastPong retrieves the time of the last successful contact from remote node.
+func (db *nodeDB) lastPong(id NodeID) time.Time {
+	return time.Unix(db.fetchInt64(makeKey(id, nodeDBDiscoverPong)), 0)
+}
+
+// updateLastPong updates the last time a remote node successfully contacted.
+func (db *nodeDB) updateLastPong(id NodeID, instance time.Time) error {
+	return db.storeInt64(makeKey(id, nodeDBDiscoverPong), instance.Unix())
+}
+
+// findFails retrieves the number of findnode failures since bonding.
+func (db *nodeDB) findFails(id NodeID) int {
+	return int(db.fetchInt64(makeKey(id, nodeDBDiscoverFindFails)))
+}
+
+// updateFindFails updates the number of findnode failures since bonding.
+func (db *nodeDB) updateFindFails(id NodeID, fails int) error {
+	return db.storeInt64(makeKey(id, nodeDBDiscoverFindFails), int64(fails))
+}
+
+// localEndpoint returns the last local endpoint communicated to the
+// given remote node.
+func (db *nodeDB) localEndpoint(id NodeID) *rpcEndpoint {
+	var ep rpcEndpoint
+	if err := db.fetchRLP(makeKey(id, nodeDBDiscoverLocalEndpoint), &ep); err != nil {
+		return nil
+	}
+	return &ep
+}
+
+func (db *nodeDB) updateLocalEndpoint(id NodeID, ep rpcEndpoint) error {
+	return db.storeRLP(makeKey(id, nodeDBDiscoverLocalEndpoint), &ep)
+}
+
+// querySeeds retrieves random nodes to be used as potential seed nodes
+// for bootstrapping.
+func (db *nodeDB) querySeeds(n int, maxAge time.Duration) []*Node {
+	var (
+		now   = time.Now()
+		nodes = make([]*Node, 0, n)
+		it    = db.lvl.NewIterator(nil, nil)
+		id    NodeID
+	)
+	defer it.Release()
+
+seek:
+	for seeks := 0; len(nodes) < n && seeks < n*5; seeks++ {
+		// Seek to a random entry. The first byte is incremented by a
+		// random amount each time in order to increase the likelihood
+		// of hitting all existing nodes in very small databases.
+		ctr := id[0]
+		rand.Read(id[:])
+		id[0] = ctr + id[0]%16
+		it.Seek(makeKey(id, nodeDBDiscoverRoot))
+
+		n := nextNode(it)
+		if n == nil {
+			id[0] = 0
+			continue seek // iterator exhausted
+		}
+		if n.ID == db.self {
+			continue seek
+		}
+		if now.Sub(db.lastPong(n.ID)) > maxAge {
+			continue seek
+		}
+		for i := range nodes {
+			if nodes[i].ID == n.ID {
+				continue seek // duplicate
+			}
+		}
+		nodes = append(nodes, n)
+	}
+	return nodes
+}
+
+func (db *nodeDB) fetchTopicRegTickets(id NodeID) (issued, used uint32) {
+	key := makeKey(id, nodeDBTopicRegTickets)
+	blob, _ := db.lvl.Get(key, nil)
+	if len(blob) != 8 {
+		return 0, 0
+	}
+	issued = binary.BigEndian.Uint32(blob[0:4])
+	used = binary.BigEndian.Uint32(blob[4:8])
+	return
+}
+
+func (db *nodeDB) updateTopicRegTickets(id NodeID, issued, used uint32) error {
+	key := makeKey(id, nodeDBTopicRegTickets)
+	blob := make([]byte, 8)
+	binary.BigEndian.PutUint32(blob[0:4], issued)
+	binary.BigEndian.PutUint32(blob[4:8], used)
+	return db.lvl.Put(key, blob, nil)
+}
+
+// reads the next node record from the iterator, skipping over other
+// database entries.
+func nextNode(it iterator.Iterator) *Node {
+	for end := false; !end; end = !it.Next() {
+		id, field := splitKey(it.Key())
+		if field != nodeDBDiscoverRoot {
+			continue
+		}
+		var n Node
+		if err := rlp.DecodeBytes(it.Value(), &n); err != nil {
+			if glog.V(logger.Warn) {
+				glog.Errorf("invalid node %x: %v", id, err)
+			}
+			continue
+		}
+		return &n
+	}
+	return nil
+}
+
+// close flushes and closes the database files.
+func (db *nodeDB) close() {
+	close(db.quit)
+	db.lvl.Close()
+}
diff --git a/p2p/discv5/database_test.go b/p2p/discv5/database_test.go
new file mode 100644
index 000000000..4d3330ed2
--- /dev/null
+++ b/p2p/discv5/database_test.go
@@ -0,0 +1,380 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+	"time"
+)
+
+var nodeDBKeyTests = []struct {
+	id    NodeID
+	field string
+	key   []byte
+}{
+	{
+		id:    NodeID{},
+		field: "version",
+		key:   []byte{0x76, 0x65, 0x72, 0x73, 0x69, 0x6f, 0x6e}, // field
+	},
+	{
+		id:    MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+		field: ":discover",
+		key: []byte{0x6e, 0x3a, // prefix
+			0x1d, 0xd9, 0xd6, 0x5c, 0x45, 0x52, 0xb5, 0xeb, // node id
+			0x43, 0xd5, 0xad, 0x55, 0xa2, 0xee, 0x3f, 0x56, //
+			0xc6, 0xcb, 0xc1, 0xc6, 0x4a, 0x5c, 0x8d, 0x65, //
+			0x9f, 0x51, 0xfc, 0xd5, 0x1b, 0xac, 0xe2, 0x43, //
+			0x51, 0x23, 0x2b, 0x8d, 0x78, 0x21, 0x61, 0x7d, //
+			0x2b, 0x29, 0xb5, 0x4b, 0x81, 0xcd, 0xef, 0xb9, //
+			0xb3, 0xe9, 0xc3, 0x7d, 0x7f, 0xd5, 0xf6, 0x32, //
+			0x70, 0xbc, 0xc9, 0xe1, 0xa6, 0xf6, 0xa4, 0x39, //
+			0x3a, 0x64, 0x69, 0x73, 0x63, 0x6f, 0x76, 0x65, 0x72, // field
+		},
+	},
+}
+
+func TestNodeDBKeys(t *testing.T) {
+	for i, tt := range nodeDBKeyTests {
+		if key := makeKey(tt.id, tt.field); !bytes.Equal(key, tt.key) {
+			t.Errorf("make test %d: key mismatch: have 0x%x, want 0x%x", i, key, tt.key)
+		}
+		id, field := splitKey(tt.key)
+		if !bytes.Equal(id[:], tt.id[:]) {
+			t.Errorf("split test %d: id mismatch: have 0x%x, want 0x%x", i, id, tt.id)
+		}
+		if field != tt.field {
+			t.Errorf("split test %d: field mismatch: have 0x%x, want 0x%x", i, field, tt.field)
+		}
+	}
+}
+
+var nodeDBInt64Tests = []struct {
+	key   []byte
+	value int64
+}{
+	{key: []byte{0x01}, value: 1},
+	{key: []byte{0x02}, value: 2},
+	{key: []byte{0x03}, value: 3},
+}
+
+func TestNodeDBInt64(t *testing.T) {
+	db, _ := newNodeDB("", Version, NodeID{})
+	defer db.close()
+
+	tests := nodeDBInt64Tests
+	for i := 0; i < len(tests); i++ {
+		// Insert the next value
+		if err := db.storeInt64(tests[i].key, tests[i].value); err != nil {
+			t.Errorf("test %d: failed to store value: %v", i, err)
+		}
+		// Check all existing and non existing values
+		for j := 0; j < len(tests); j++ {
+			num := db.fetchInt64(tests[j].key)
+			switch {
+			case j <= i && num != tests[j].value:
+				t.Errorf("test %d, item %d: value mismatch: have %v, want %v", i, j, num, tests[j].value)
+			case j > i && num != 0:
+				t.Errorf("test %d, item %d: value mismatch: have %v, want %v", i, j, num, 0)
+			}
+		}
+	}
+}
+
+func TestNodeDBFetchStore(t *testing.T) {
+	node := NewNode(
+		MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+		net.IP{192, 168, 0, 1},
+		30303,
+		30303,
+	)
+	inst := time.Now()
+	num := 314
+
+	db, _ := newNodeDB("", Version, NodeID{})
+	defer db.close()
+
+	// Check fetch/store operations on a node ping object
+	if stored := db.lastPing(node.ID); stored.Unix() != 0 {
+		t.Errorf("ping: non-existing object: %v", stored)
+	}
+	if err := db.updateLastPing(node.ID, inst); err != nil {
+		t.Errorf("ping: failed to update: %v", err)
+	}
+	if stored := db.lastPing(node.ID); stored.Unix() != inst.Unix() {
+		t.Errorf("ping: value mismatch: have %v, want %v", stored, inst)
+	}
+	// Check fetch/store operations on a node pong object
+	if stored := db.lastPong(node.ID); stored.Unix() != 0 {
+		t.Errorf("pong: non-existing object: %v", stored)
+	}
+	if err := db.updateLastPong(node.ID, inst); err != nil {
+		t.Errorf("pong: failed to update: %v", err)
+	}
+	if stored := db.lastPong(node.ID); stored.Unix() != inst.Unix() {
+		t.Errorf("pong: value mismatch: have %v, want %v", stored, inst)
+	}
+	// Check fetch/store operations on a node findnode-failure object
+	if stored := db.findFails(node.ID); stored != 0 {
+		t.Errorf("find-node fails: non-existing object: %v", stored)
+	}
+	if err := db.updateFindFails(node.ID, num); err != nil {
+		t.Errorf("find-node fails: failed to update: %v", err)
+	}
+	if stored := db.findFails(node.ID); stored != num {
+		t.Errorf("find-node fails: value mismatch: have %v, want %v", stored, num)
+	}
+	// Check fetch/store operations on an actual node object
+	if stored := db.node(node.ID); stored != nil {
+		t.Errorf("node: non-existing object: %v", stored)
+	}
+	if err := db.updateNode(node); err != nil {
+		t.Errorf("node: failed to update: %v", err)
+	}
+	if stored := db.node(node.ID); stored == nil {
+		t.Errorf("node: not found")
+	} else if !reflect.DeepEqual(stored, node) {
+		t.Errorf("node: data mismatch: have %v, want %v", stored, node)
+	}
+}
+
+var nodeDBSeedQueryNodes = []struct {
+	node *Node
+	pong time.Time
+}{
+	// This one should not be in the result set because its last
+	// pong time is too far in the past.
+	{
+		node: NewNode(
+			MustHexID("0x84d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 3},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-3 * time.Hour),
+	},
+	// This one shouldn't be in in the result set because its
+	// nodeID is the local node's ID.
+	{
+		node: NewNode(
+			MustHexID("0x57d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 3},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-4 * time.Second),
+	},
+
+	// These should be in the result set.
+	{
+		node: NewNode(
+			MustHexID("0x22d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 1},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-2 * time.Second),
+	},
+	{
+		node: NewNode(
+			MustHexID("0x44d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 2},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-3 * time.Second),
+	},
+	{
+		node: NewNode(
+			MustHexID("0xe2d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 3},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-1 * time.Second),
+	},
+}
+
+func TestNodeDBSeedQuery(t *testing.T) {
+	db, _ := newNodeDB("", Version, nodeDBSeedQueryNodes[1].node.ID)
+	defer db.close()
+
+	// Insert a batch of nodes for querying
+	for i, seed := range nodeDBSeedQueryNodes {
+		if err := db.updateNode(seed.node); err != nil {
+			t.Fatalf("node %d: failed to insert: %v", i, err)
+		}
+		if err := db.updateLastPong(seed.node.ID, seed.pong); err != nil {
+			t.Fatalf("node %d: failed to insert lastPong: %v", i, err)
+		}
+	}
+
+	// Retrieve the entire batch and check for duplicates
+	seeds := db.querySeeds(len(nodeDBSeedQueryNodes)*2, time.Hour)
+	have := make(map[NodeID]struct{})
+	for _, seed := range seeds {
+		have[seed.ID] = struct{}{}
+	}
+	want := make(map[NodeID]struct{})
+	for _, seed := range nodeDBSeedQueryNodes[2:] {
+		want[seed.node.ID] = struct{}{}
+	}
+	if len(seeds) != len(want) {
+		t.Errorf("seed count mismatch: have %v, want %v", len(seeds), len(want))
+	}
+	for id, _ := range have {
+		if _, ok := want[id]; !ok {
+			t.Errorf("extra seed: %v", id)
+		}
+	}
+	for id, _ := range want {
+		if _, ok := have[id]; !ok {
+			t.Errorf("missing seed: %v", id)
+		}
+	}
+}
+
+func TestNodeDBPersistency(t *testing.T) {
+	root, err := ioutil.TempDir("", "nodedb-")
+	if err != nil {
+		t.Fatalf("failed to create temporary data folder: %v", err)
+	}
+	defer os.RemoveAll(root)
+
+	var (
+		testKey = []byte("somekey")
+		testInt = int64(314)
+	)
+
+	// Create a persistent database and store some values
+	db, err := newNodeDB(filepath.Join(root, "database"), Version, NodeID{})
+	if err != nil {
+		t.Fatalf("failed to create persistent database: %v", err)
+	}
+	if err := db.storeInt64(testKey, testInt); err != nil {
+		t.Fatalf("failed to store value: %v.", err)
+	}
+	db.close()
+
+	// Reopen the database and check the value
+	db, err = newNodeDB(filepath.Join(root, "database"), Version, NodeID{})
+	if err != nil {
+		t.Fatalf("failed to open persistent database: %v", err)
+	}
+	if val := db.fetchInt64(testKey); val != testInt {
+		t.Fatalf("value mismatch: have %v, want %v", val, testInt)
+	}
+	db.close()
+
+	// Change the database version and check flush
+	db, err = newNodeDB(filepath.Join(root, "database"), Version+1, NodeID{})
+	if err != nil {
+		t.Fatalf("failed to open persistent database: %v", err)
+	}
+	if val := db.fetchInt64(testKey); val != 0 {
+		t.Fatalf("value mismatch: have %v, want %v", val, 0)
+	}
+	db.close()
+}
+
+var nodeDBExpirationNodes = []struct {
+	node *Node
+	pong time.Time
+	exp  bool
+}{
+	{
+		node: NewNode(
+			MustHexID("0x01d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 1},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-nodeDBNodeExpiration + time.Minute),
+		exp:  false,
+	}, {
+		node: NewNode(
+			MustHexID("0x02d9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 2},
+			30303,
+			30303,
+		),
+		pong: time.Now().Add(-nodeDBNodeExpiration - time.Minute),
+		exp:  true,
+	},
+}
+
+func TestNodeDBExpiration(t *testing.T) {
+	db, _ := newNodeDB("", Version, NodeID{})
+	defer db.close()
+
+	// Add all the test nodes and set their last pong time
+	for i, seed := range nodeDBExpirationNodes {
+		if err := db.updateNode(seed.node); err != nil {
+			t.Fatalf("node %d: failed to insert: %v", i, err)
+		}
+		if err := db.updateLastPong(seed.node.ID, seed.pong); err != nil {
+			t.Fatalf("node %d: failed to update pong: %v", i, err)
+		}
+	}
+	// Expire some of them, and check the rest
+	if err := db.expireNodes(); err != nil {
+		t.Fatalf("failed to expire nodes: %v", err)
+	}
+	for i, seed := range nodeDBExpirationNodes {
+		node := db.node(seed.node.ID)
+		if (node == nil && !seed.exp) || (node != nil && seed.exp) {
+			t.Errorf("node %d: expiration mismatch: have %v, want %v", i, node, seed.exp)
+		}
+	}
+}
+
+func TestNodeDBSelfExpiration(t *testing.T) {
+	// Find a node in the tests that shouldn't expire, and assign it as self
+	var self NodeID
+	for _, node := range nodeDBExpirationNodes {
+		if !node.exp {
+			self = node.node.ID
+			break
+		}
+	}
+	db, _ := newNodeDB("", Version, self)
+	defer db.close()
+
+	// Add all the test nodes and set their last pong time
+	for i, seed := range nodeDBExpirationNodes {
+		if err := db.updateNode(seed.node); err != nil {
+			t.Fatalf("node %d: failed to insert: %v", i, err)
+		}
+		if err := db.updateLastPong(seed.node.ID, seed.pong); err != nil {
+			t.Fatalf("node %d: failed to update pong: %v", i, err)
+		}
+	}
+	// Expire the nodes and make sure self has been evacuated too
+	if err := db.expireNodes(); err != nil {
+		t.Fatalf("failed to expire nodes: %v", err)
+	}
+	node := db.node(self)
+	if node != nil {
+		t.Errorf("self not evacuated")
+	}
+}
diff --git a/p2p/discv5/net.go b/p2p/discv5/net.go
new file mode 100644
index 000000000..afc92e99f
--- /dev/null
+++ b/p2p/discv5/net.go
@@ -0,0 +1,1200 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"errors"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/crypto/sha3"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/p2p/nat"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+var (
+	errInvalidEvent = errors.New("invalid in current state")
+	errNoQuery      = errors.New("no pending query")
+	errWrongAddress = errors.New("unknown sender address")
+)
+
+const (
+	autoRefreshInterval = 1 * time.Hour
+	seedCount           = 30
+	seedMaxAge          = 5 * 24 * time.Hour
+)
+
+const testTopic = "foo"
+
+const (
+	printDebugLogs   = false
+	printTestImgLogs = false
+)
+
+func debugLog(s string) {
+	if printDebugLogs {
+		fmt.Println(s)
+	}
+}
+
+// BootNodes are the enode URLs of the P2P bootstrap nodes for the experimental RLPx v5 "Topic Discovery" network
+// warning: local bootnodes for testing!!!
+var BootNodes = []*Node{
+	//MustParseNode("enode://6f974ede10d07334e7e651c1501cb540d087dd3a6dea81432620895c913f281790b49459d72cb8011bfbbfbd24fad956356189c31b7181a96cd44ccfb68bfc71@127.0.0.1:30301"),
+	MustParseNode("enode://0cc5f5ffb5d9098c8b8c62325f3797f56509bff942704687b6530992ac706e2cb946b90a34f1f19548cd3c7baccbcaea354531e5983c7d1bc0dee16ce4b6440b@40.118.3.223:30305"),
+}
+
+// Network manages the table and all protocol interaction.
+type Network struct {
+	db   *nodeDB // database of known nodes
+	conn transport
+
+	closed           chan struct{}          // closed when loop is done
+	closeReq         chan struct{}          // 'request to close'
+	refreshReq       chan []*Node           // lookups ask for refresh on this channel
+	refreshResp      chan (<-chan struct{}) // ...and get the channel to block on from this one
+	read             chan ingressPacket     // ingress packets arrive here
+	timeout          chan timeoutEvent
+	queryReq         chan *findnodeQuery // lookups submit findnode queries on this channel
+	tableOpReq       chan func()
+	tableOpResp      chan struct{}
+	topicRegisterReq chan topicRegisterReq
+	topicSearchReq   chan topicSearchReq
+	bucketFillChn    chan chan struct{}
+
+	// State of the main loop.
+	tab           *Table
+	topictab      *topicTable
+	ticketStore   *ticketStore
+	nursery       []*Node
+	nodes         map[NodeID]*Node // tracks active nodes with state != known
+	timeoutTimers map[timeoutEvent]*time.Timer
+
+	// Revalidation queues.
+	// Nodes put on these queues will be pinged eventually.
+	slowRevalidateQueue []*Node
+	fastRevalidateQueue []*Node
+
+	// Buffers for state transition.
+	sendBuf []*ingressPacket
+}
+
+// transport is implemented by the UDP transport.
+// it is an interface so we can test without opening lots of UDP
+// sockets and without generating a private key.
+type transport interface {
+	sendPing(remote *Node, remoteAddr *net.UDPAddr, topics []Topic) (hash []byte)
+	sendNeighbours(remote *Node, nodes []*Node)
+	sendFindnodeHash(remote *Node, target common.Hash)
+	sendTopicRegister(remote *Node, topics []Topic, topicIdx int, pong []byte)
+	sendTopicNodes(remote *Node, queryHash common.Hash, nodes []*Node)
+
+	send(remote *Node, ptype nodeEvent, p interface{}) (hash []byte)
+
+	localAddr() *net.UDPAddr
+	Close()
+}
+
+type findnodeQuery struct {
+	remote   *Node
+	target   common.Hash
+	reply    chan<- []*Node
+	nresults int // counter for received nodes
+}
+
+type topicRegisterReq struct {
+	add   bool
+	topic Topic
+}
+
+type topicSearchReq struct {
+	topic Topic
+	found chan<- string
+}
+
+type timeoutEvent struct {
+	ev   nodeEvent
+	node *Node
+}
+
+func newNetwork(conn transport, ourPubkey ecdsa.PublicKey, natm nat.Interface, dbPath string) (*Network, error) {
+	ourID := PubkeyID(&ourPubkey)
+
+	var db *nodeDB
+	if dbPath != "<no database>" {
+		var err error
+		if db, err = newNodeDB(dbPath, Version, ourID); err != nil {
+			return nil, err
+		}
+	}
+
+	tab := newTable(ourID, conn.localAddr())
+	net := &Network{
+		db:               db,
+		conn:             conn,
+		tab:              tab,
+		topictab:         newTopicTable(db, tab.self),
+		ticketStore:      newTicketStore(),
+		refreshReq:       make(chan []*Node),
+		refreshResp:      make(chan (<-chan struct{})),
+		closed:           make(chan struct{}),
+		closeReq:         make(chan struct{}),
+		read:             make(chan ingressPacket, 100),
+		timeout:          make(chan timeoutEvent),
+		timeoutTimers:    make(map[timeoutEvent]*time.Timer),
+		tableOpReq:       make(chan func()),
+		tableOpResp:      make(chan struct{}),
+		queryReq:         make(chan *findnodeQuery),
+		topicRegisterReq: make(chan topicRegisterReq),
+		topicSearchReq:   make(chan topicSearchReq),
+		bucketFillChn:    make(chan chan struct{}, 1),
+		nodes:            make(map[NodeID]*Node),
+	}
+	go net.loop()
+	return net, nil
+}
+
+// Close terminates the network listener and flushes the node database.
+func (net *Network) Close() {
+	net.conn.Close()
+	select {
+	case <-net.closed:
+	case net.closeReq <- struct{}{}:
+		<-net.closed
+	}
+}
+
+// Self returns the local node.
+// The returned node should not be modified by the caller.
+func (net *Network) Self() *Node {
+	return net.tab.self
+}
+
+// ReadRandomNodes fills the given slice with random nodes from the
+// table. It will not write the same node more than once. The nodes in
+// the slice are copies and can be modified by the caller.
+func (net *Network) ReadRandomNodes(buf []*Node) (n int) {
+	net.reqTableOp(func() { n = net.tab.readRandomNodes(buf) })
+	return n
+}
+
+// SetFallbackNodes sets the initial points of contact. These nodes
+// are used to connect to the network if the table is empty and there
+// are no known nodes in the database.
+func (net *Network) SetFallbackNodes(nodes []*Node) error {
+	nursery := make([]*Node, 0, len(nodes))
+	for _, n := range nodes {
+		if err := n.validateComplete(); err != nil {
+			return fmt.Errorf("bad bootstrap/fallback node %q (%v)", n, err)
+		}
+		// Recompute cpy.sha because the node might not have been
+		// created by NewNode or ParseNode.
+		cpy := *n
+		cpy.sha = crypto.Keccak256Hash(n.ID[:])
+		nursery = append(nursery, &cpy)
+	}
+	net.reqRefresh(nursery)
+	return nil
+}
+
+// Resolve searches for a specific node with the given ID.
+// It returns nil if the node could not be found.
+func (net *Network) Resolve(targetID NodeID) *Node {
+	result := net.lookup(crypto.Keccak256Hash(targetID[:]), true)
+	for _, n := range result {
+		if n.ID == targetID {
+			return n
+		}
+	}
+	return nil
+}
+
+// Lookup performs a network search for nodes close
+// to the given target. It approaches the target by querying
+// nodes that are closer to it on each iteration.
+// The given target does not need to be an actual node
+// identifier.
+//
+// The local node may be included in the result.
+func (net *Network) Lookup(targetID NodeID) []*Node {
+	return net.lookup(crypto.Keccak256Hash(targetID[:]), false)
+}
+
+func (net *Network) lookup(target common.Hash, stopOnMatch bool) []*Node {
+	var (
+		asked          = make(map[NodeID]bool)
+		seen           = make(map[NodeID]bool)
+		reply          = make(chan []*Node, alpha)
+		result         = nodesByDistance{target: target}
+		pendingQueries = 0
+	)
+	// Get initial answers from the local node.
+	result.push(net.tab.self, bucketSize)
+	for {
+		// Ask the α closest nodes that we haven't asked yet.
+		for i := 0; i < len(result.entries) && pendingQueries < alpha; i++ {
+			n := result.entries[i]
+			if !asked[n.ID] {
+				asked[n.ID] = true
+				pendingQueries++
+				net.reqQueryFindnode(n, target, reply)
+			}
+		}
+		if pendingQueries == 0 {
+			// We have asked all closest nodes, stop the search.
+			break
+		}
+		// Wait for the next reply.
+		for _, n := range <-reply {
+			if n != nil && !seen[n.ID] {
+				seen[n.ID] = true
+				result.push(n, bucketSize)
+				if stopOnMatch && n.sha == target {
+					return result.entries
+				}
+			}
+		}
+		pendingQueries--
+	}
+	return result.entries
+}
+
+func (net *Network) RegisterTopic(topic Topic, stop <-chan struct{}) {
+	select {
+	case net.topicRegisterReq <- topicRegisterReq{true, topic}:
+	case <-net.closed:
+		return
+	}
+	select {
+	case <-net.closed:
+	case <-stop:
+		select {
+		case net.topicRegisterReq <- topicRegisterReq{false, topic}:
+		case <-net.closed:
+		}
+	}
+}
+
+func (net *Network) SearchTopic(topic Topic, stop <-chan struct{}, found chan<- string) {
+	select {
+	case net.topicSearchReq <- topicSearchReq{topic, found}:
+	case <-net.closed:
+		return
+	}
+	select {
+	case <-net.closed:
+	case <-stop:
+		select {
+		case net.topicSearchReq <- topicSearchReq{topic, nil}:
+		case <-net.closed:
+		}
+	}
+}
+
+func (net *Network) reqRefresh(nursery []*Node) <-chan struct{} {
+	select {
+	case net.refreshReq <- nursery:
+		return <-net.refreshResp
+	case <-net.closed:
+		return net.closed
+	}
+}
+
+func (net *Network) reqQueryFindnode(n *Node, target common.Hash, reply chan []*Node) bool {
+	q := &findnodeQuery{remote: n, target: target, reply: reply}
+	select {
+	case net.queryReq <- q:
+		return true
+	case <-net.closed:
+		return false
+	}
+}
+
+func (net *Network) reqReadPacket(pkt ingressPacket) {
+	select {
+	case net.read <- pkt:
+	case <-net.closed:
+	}
+}
+
+func (net *Network) reqTableOp(f func()) (called bool) {
+	select {
+	case net.tableOpReq <- f:
+		<-net.tableOpResp
+		return true
+	case <-net.closed:
+		return false
+	}
+}
+
+// TODO: external address handling.
+
+func (net *Network) loop() {
+	var (
+		refreshTimer = time.NewTicker(autoRefreshInterval)
+		refreshDone  chan struct{} // closed when the 'refresh' lookup has ended
+	)
+
+	// Tracking the next ticket to register.
+	var (
+		nextTicket        *ticketRef
+		nextRegisterTimer *time.Timer
+		nextRegisterTime  <-chan time.Time
+	)
+	defer func() {
+		if nextRegisterTimer != nil {
+			nextRegisterTimer.Stop()
+		}
+	}()
+	resetNextTicket := func() {
+		t, timeout := net.ticketStore.nextFilteredTicket()
+		if t != nextTicket {
+			nextTicket = t
+			if nextRegisterTimer != nil {
+				nextRegisterTimer.Stop()
+				nextRegisterTime = nil
+			}
+			if t != nil {
+				nextRegisterTimer = time.NewTimer(timeout)
+				nextRegisterTime = nextRegisterTimer.C
+			}
+		}
+	}
+
+	// Tracking registration and search lookups.
+	var (
+		topicRegisterLookupTarget lookupInfo
+		topicRegisterLookupDone   chan []*Node
+		topicRegisterLookupTick   = time.NewTimer(0)
+		topicSearchLookupTarget   lookupInfo
+	)
+	topicSearchLookupDone := make(chan []*Node, 1)
+	<-topicRegisterLookupTick.C
+
+	statsDump := time.NewTicker(10 * time.Second)
+
+loop:
+	for {
+		resetNextTicket()
+
+		select {
+		case <-net.closeReq:
+			debugLog("<-net.closeReq")
+			break loop
+
+		// Ingress packet handling.
+		case pkt := <-net.read:
+			debugLog("<-net.read")
+			n := net.internNode(&pkt)
+			prestate := n.state
+			status := "ok"
+			if err := net.handle(n, pkt.ev, &pkt); err != nil {
+				status = err.Error()
+			}
+			if glog.V(logger.Detail) {
+				glog.Infof("<<< (%d) %v from %x@%v: %v -> %v (%v)",
+					net.tab.count, pkt.ev, pkt.remoteID[:8], pkt.remoteAddr, prestate, n.state, status)
+			}
+			// TODO: persist state if n.state goes >= known, delete if it goes <= known
+
+		// State transition timeouts.
+		case timeout := <-net.timeout:
+			debugLog("<-net.timeout")
+			if net.timeoutTimers[timeout] == nil {
+				// Stale timer (was aborted).
+				continue
+			}
+			delete(net.timeoutTimers, timeout)
+			prestate := timeout.node.state
+			status := "ok"
+			if err := net.handle(timeout.node, timeout.ev, nil); err != nil {
+				status = err.Error()
+			}
+			if glog.V(logger.Detail) {
+				glog.Infof("--- (%d) %v for %x@%v: %v -> %v (%v)",
+					net.tab.count, timeout.ev, timeout.node.ID[:8], timeout.node.addr(), prestate, timeout.node.state, status)
+			}
+
+		// Querying.
+		case q := <-net.queryReq:
+			debugLog("<-net.queryReq")
+			if !q.start(net) {
+				q.remote.deferQuery(q)
+			}
+
+		// Interacting with the table.
+		case f := <-net.tableOpReq:
+			debugLog("<-net.tableOpReq")
+			f()
+			net.tableOpResp <- struct{}{}
+
+		// Topic registration stuff.
+		case req := <-net.topicRegisterReq:
+			debugLog("<-net.topicRegisterReq")
+			if !req.add {
+				net.ticketStore.removeRegisterTopic(req.topic)
+				continue
+			}
+			net.ticketStore.addTopic(req.topic, true)
+			// If we're currently waiting idle (nothing to look up), give the ticket store a
+			// chance to start it sooner. This should speed up convergence of the radius
+			// determination for new topics.
+			// if topicRegisterLookupDone == nil {
+			if topicRegisterLookupTarget.target == (common.Hash{}) {
+				debugLog("topicRegisterLookupTarget == null")
+				if topicRegisterLookupTick.Stop() {
+					<-topicRegisterLookupTick.C
+				}
+				target, delay := net.ticketStore.nextRegisterLookup()
+				topicRegisterLookupTarget = target
+				topicRegisterLookupTick.Reset(delay)
+			}
+
+		case nodes := <-topicRegisterLookupDone:
+			debugLog("<-topicRegisterLookupDone")
+			net.ticketStore.registerLookupDone(topicRegisterLookupTarget, nodes, func(n *Node) []byte {
+				net.ping(n, n.addr())
+				return n.pingEcho
+			})
+			target, delay := net.ticketStore.nextRegisterLookup()
+			topicRegisterLookupTarget = target
+			topicRegisterLookupTick.Reset(delay)
+			topicRegisterLookupDone = nil
+
+		case <-topicRegisterLookupTick.C:
+			debugLog("<-topicRegisterLookupTick")
+			if (topicRegisterLookupTarget.target == common.Hash{}) {
+				target, delay := net.ticketStore.nextRegisterLookup()
+				topicRegisterLookupTarget = target
+				topicRegisterLookupTick.Reset(delay)
+				topicRegisterLookupDone = nil
+			} else {
+				topicRegisterLookupDone = make(chan []*Node)
+				target := topicRegisterLookupTarget.target
+				go func() { topicRegisterLookupDone <- net.lookup(target, false) }()
+			}
+
+		case <-nextRegisterTime:
+			debugLog("<-nextRegisterTime")
+			net.ticketStore.ticketRegistered(*nextTicket)
+			//fmt.Println("sendTopicRegister", nextTicket.t.node.addr().String(), nextTicket.t.topics, nextTicket.idx, nextTicket.t.pong)
+			net.conn.sendTopicRegister(nextTicket.t.node, nextTicket.t.topics, nextTicket.idx, nextTicket.t.pong)
+
+		case req := <-net.topicSearchReq:
+			debugLog("<-net.topicSearchReq")
+			if req.found == nil {
+				net.ticketStore.removeSearchTopic(req.topic)
+				continue
+			}
+			net.ticketStore.addSearchTopic(req.topic, req.found)
+			if (topicSearchLookupTarget.target == common.Hash{}) {
+				topicSearchLookupDone <- nil
+			}
+
+		case nodes := <-topicSearchLookupDone:
+			debugLog("<-topicSearchLookupDone")
+			net.ticketStore.searchLookupDone(topicSearchLookupTarget, nodes, func(n *Node) []byte {
+				net.ping(n, n.addr())
+				return n.pingEcho
+			}, func(n *Node, topic Topic) []byte {
+				return net.conn.send(n, topicQueryPacket, topicQuery{Topic: topic}) // TODO: set expiration
+			})
+			topicSearchLookupTarget = net.ticketStore.nextSearchLookup()
+			target := topicSearchLookupTarget.target
+			if (target != common.Hash{}) {
+				go func() { topicSearchLookupDone <- net.lookup(target, false) }()
+			}
+
+		case <-statsDump.C:
+			debugLog("<-statsDump.C")
+			/*r, ok := net.ticketStore.radius[testTopic]
+			if !ok {
+				fmt.Printf("(%x) no radius @ %v\n", net.tab.self.ID[:8], time.Now())
+			} else {
+				topics := len(net.ticketStore.tickets)
+				tickets := len(net.ticketStore.nodes)
+				rad := r.radius / (maxRadius/10000+1)
+				fmt.Printf("(%x) topics:%d radius:%d tickets:%d @ %v\n", net.tab.self.ID[:8], topics, rad, tickets, time.Now())
+			}*/
+
+			tm := mclock.Now()
+			for topic, r := range net.ticketStore.radius {
+				if printTestImgLogs {
+					rad := r.radius / (maxRadius/1000000 + 1)
+					minrad := r.minRadius / (maxRadius/1000000 + 1)
+					fmt.Printf("*R %d %v %016x %v\n", tm/1000000, topic, net.tab.self.sha[:8], rad)
+					fmt.Printf("*MR %d %v %016x %v\n", tm/1000000, topic, net.tab.self.sha[:8], minrad)
+				}
+			}
+			for topic, t := range net.topictab.topics {
+				wp := t.wcl.nextWaitPeriod(tm)
+				if printTestImgLogs {
+					fmt.Printf("*W %d %v %016x %d\n", tm/1000000, topic, net.tab.self.sha[:8], wp/1000000)
+				}
+			}
+
+		// Periodic / lookup-initiated bucket refresh.
+		case <-refreshTimer.C:
+			debugLog("<-refreshTimer.C")
+			// TODO: ideally we would start the refresh timer after
+			// fallback nodes have been set for the first time.
+			if refreshDone == nil {
+				refreshDone = make(chan struct{})
+				net.refresh(refreshDone)
+			}
+		case doneChn := <-net.bucketFillChn:
+			debugLog("bucketFill")
+			net.bucketFill(doneChn)
+		case newNursery := <-net.refreshReq:
+			debugLog("<-net.refreshReq")
+			if newNursery != nil {
+				net.nursery = newNursery
+			}
+			if refreshDone == nil {
+				refreshDone = make(chan struct{})
+				net.refresh(refreshDone)
+			}
+			net.refreshResp <- refreshDone
+		case <-refreshDone:
+			debugLog("<-net.refreshDone")
+			refreshDone = nil
+		}
+	}
+	debugLog("loop stopped")
+
+	glog.V(logger.Debug).Infof("shutting down")
+	if net.conn != nil {
+		net.conn.Close()
+	}
+	if refreshDone != nil {
+		// TODO: wait for pending refresh.
+		//<-refreshResults
+	}
+	// Cancel all pending timeouts.
+	for _, timer := range net.timeoutTimers {
+		timer.Stop()
+	}
+	if net.db != nil {
+		net.db.close()
+	}
+	close(net.closed)
+}
+
+// Everything below runs on the Network.loop goroutine
+// and can modify Node, Table and Network at any time without locking.
+
+func (net *Network) refresh(done chan<- struct{}) {
+	var seeds []*Node
+	if net.db != nil {
+		seeds = net.db.querySeeds(seedCount, seedMaxAge)
+	}
+	if len(seeds) == 0 {
+		seeds = net.nursery
+	}
+	if len(seeds) == 0 {
+		glog.V(logger.Detail).Info("no seed nodes found")
+		close(done)
+		return
+	}
+	for _, n := range seeds {
+		if glog.V(logger.Debug) {
+			var age string
+			if net.db != nil {
+				age = time.Since(net.db.lastPong(n.ID)).String()
+			} else {
+				age = "unknown"
+			}
+			glog.Infof("seed node (age %s): %v", age, n)
+		}
+		n = net.internNodeFromDB(n)
+		if n.state == unknown {
+			net.transition(n, verifyinit)
+		}
+		// Force-add the seed node so Lookup does something.
+		// It will be deleted again if verification fails.
+		net.tab.add(n)
+	}
+	// Start self lookup to fill up the buckets.
+	go func() {
+		net.Lookup(net.tab.self.ID)
+		close(done)
+	}()
+}
+
+func (net *Network) bucketFill(done chan<- struct{}) {
+	target := net.tab.chooseBucketFillTarget()
+	go func() {
+		net.lookup(target, false)
+		close(done)
+	}()
+}
+
+func (net *Network) BucketFill() {
+	done := make(chan struct{})
+	select {
+	case net.bucketFillChn <- done:
+		<-done
+	case <-net.closed:
+		close(done)
+	}
+}
+
+// Node Interning.
+
+func (net *Network) internNode(pkt *ingressPacket) *Node {
+	if n := net.nodes[pkt.remoteID]; n != nil {
+		return n
+	}
+	n := NewNode(pkt.remoteID, pkt.remoteAddr.IP, uint16(pkt.remoteAddr.Port), uint16(pkt.remoteAddr.Port))
+	n.state = unknown
+	net.nodes[pkt.remoteID] = n
+	return n
+}
+
+func (net *Network) internNodeFromDB(dbn *Node) *Node {
+	if n := net.nodes[dbn.ID]; n != nil {
+		return n
+	}
+	n := NewNode(dbn.ID, dbn.IP, dbn.UDP, dbn.TCP)
+	n.state = unknown
+	net.nodes[n.ID] = n
+	return n
+}
+
+func (net *Network) internNodeFromNeighbours(rn rpcNode) (n *Node, err error) {
+	if rn.ID == net.tab.self.ID {
+		return nil, errors.New("is self")
+	}
+	n = net.nodes[rn.ID]
+	if n == nil {
+		// We haven't seen this node before.
+		n, err = nodeFromRPC(rn)
+		n.state = unknown
+		if err == nil {
+			net.nodes[n.ID] = n
+		}
+		return n, err
+	}
+	if !bytes.Equal(n.IP, rn.IP) || n.UDP != rn.UDP || n.TCP != rn.TCP {
+		err = fmt.Errorf("metadata mismatch: got %v, want %v", rn, n)
+	}
+	return n, err
+}
+
+// nodeNetGuts is embedded in Node and contains fields.
+type nodeNetGuts struct {
+	// This is a cached copy of sha3(ID) which is used for node
+	// distance calculations. This is part of Node in order to make it
+	// possible to write tests that need a node at a certain distance.
+	// In those tests, the content of sha will not actually correspond
+	// with ID.
+	sha common.Hash
+
+	// State machine fields. Access to these fields
+	// is restricted to the Network.loop goroutine.
+	state             *nodeState
+	pingEcho          []byte           // hash of last ping sent by us
+	pingTopics        []Topic          // topic set sent by us in last ping
+	deferredQueries   []*findnodeQuery // queries that can't be sent yet
+	pendingNeighbours *findnodeQuery   // current query, waiting for reply
+	queryTimeouts     int
+}
+
+func (n *nodeNetGuts) deferQuery(q *findnodeQuery) {
+	n.deferredQueries = append(n.deferredQueries, q)
+}
+
+func (n *nodeNetGuts) startNextQuery(net *Network) {
+	if len(n.deferredQueries) == 0 {
+		return
+	}
+	nextq := n.deferredQueries[0]
+	if nextq.start(net) {
+		n.deferredQueries = append(n.deferredQueries[:0], n.deferredQueries[1:]...)
+	}
+}
+
+func (q *findnodeQuery) start(net *Network) bool {
+	// Satisfy queries against the local node directly.
+	if q.remote == net.tab.self {
+		closest := net.tab.closest(crypto.Keccak256Hash(q.target[:]), bucketSize)
+		q.reply <- closest.entries
+		return true
+	}
+	if q.remote.state.canQuery && q.remote.pendingNeighbours == nil {
+		net.conn.sendFindnodeHash(q.remote, q.target)
+		net.timedEvent(respTimeout, q.remote, neighboursTimeout)
+		q.remote.pendingNeighbours = q
+		return true
+	}
+	// If the node is not known yet, it won't accept queries.
+	// Initiate the transition to known.
+	// The request will be sent later when the node reaches known state.
+	if q.remote.state == unknown {
+		net.transition(q.remote, verifyinit)
+	}
+	return false
+}
+
+// Node Events (the input to the state machine).
+
+type nodeEvent uint
+
+//go:generate stringer -type=nodeEvent
+
+const (
+	invalidEvent nodeEvent = iota // zero is reserved
+
+	// Packet type events.
+	// These correspond to packet types in the UDP protocol.
+	pingPacket
+	pongPacket
+	findnodePacket
+	neighborsPacket
+	findnodeHashPacket
+	topicRegisterPacket
+	topicQueryPacket
+	topicNodesPacket
+
+	// Non-packet events.
+	// Event values in this category are allocated outside
+	// the packet type range (packet types are encoded as a single byte).
+	pongTimeout nodeEvent = iota + 256
+	pingTimeout
+	neighboursTimeout
+)
+
+// Node State Machine.
+
+type nodeState struct {
+	name     string
+	handle   func(*Network, *Node, nodeEvent, *ingressPacket) (next *nodeState, err error)
+	enter    func(*Network, *Node)
+	canQuery bool
+}
+
+func (s *nodeState) String() string {
+	return s.name
+}
+
+var (
+	unknown          *nodeState
+	verifyinit       *nodeState
+	verifywait       *nodeState
+	remoteverifywait *nodeState
+	known            *nodeState
+	contested        *nodeState
+	unresponsive     *nodeState
+)
+
+func init() {
+	unknown = &nodeState{
+		name: "unknown",
+		enter: func(net *Network, n *Node) {
+			net.tab.delete(n)
+			n.pingEcho = nil
+			// Abort active queries.
+			for _, q := range n.deferredQueries {
+				q.reply <- nil
+			}
+			n.deferredQueries = nil
+			if n.pendingNeighbours != nil {
+				n.pendingNeighbours.reply <- nil
+				n.pendingNeighbours = nil
+			}
+			n.queryTimeouts = 0
+		},
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pingPacket:
+				net.handlePing(n, pkt)
+				net.ping(n, pkt.remoteAddr)
+				return verifywait, nil
+			default:
+				return unknown, errInvalidEvent
+			}
+		},
+	}
+
+	verifyinit = &nodeState{
+		name: "verifyinit",
+		enter: func(net *Network, n *Node) {
+			net.ping(n, n.addr())
+		},
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pingPacket:
+				net.handlePing(n, pkt)
+				return verifywait, nil
+			case pongPacket:
+				err := net.handleKnownPong(n, pkt)
+				return remoteverifywait, err
+			case pongTimeout:
+				return unknown, nil
+			default:
+				return verifyinit, errInvalidEvent
+			}
+		},
+	}
+
+	verifywait = &nodeState{
+		name: "verifywait",
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pongPacket:
+				err := net.handleKnownPong(n, pkt)
+				return known, err
+			case pongTimeout:
+				return unknown, nil
+			default:
+				return verifywait, errInvalidEvent
+			}
+		},
+	}
+
+	remoteverifywait = &nodeState{
+		name: "remoteverifywait",
+		enter: func(net *Network, n *Node) {
+			net.timedEvent(respTimeout, n, pingTimeout)
+		},
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pingPacket:
+				net.handlePing(n, pkt)
+				return remoteverifywait, nil
+			case pingTimeout:
+				return known, nil
+			default:
+				return remoteverifywait, errInvalidEvent
+			}
+		},
+	}
+
+	known = &nodeState{
+		name:     "known",
+		canQuery: true,
+		enter: func(net *Network, n *Node) {
+			n.queryTimeouts = 0
+			n.startNextQuery(net)
+			// Insert into the table and start revalidation of the last node
+			// in the bucket if it is full.
+			last := net.tab.add(n)
+			if last != nil && last.state == known {
+				// TODO: do this asynchronously
+				net.transition(last, contested)
+			}
+		},
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pingPacket:
+				net.handlePing(n, pkt)
+				return known, nil
+			case pongPacket:
+				err := net.handleKnownPong(n, pkt)
+				return known, err
+			default:
+				return net.handleQueryEvent(n, ev, pkt)
+			}
+		},
+	}
+
+	contested = &nodeState{
+		name:     "contested",
+		canQuery: true,
+		enter: func(net *Network, n *Node) {
+			net.ping(n, n.addr())
+		},
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pongPacket:
+				// Node is still alive.
+				err := net.handleKnownPong(n, pkt)
+				return known, err
+			case pongTimeout:
+				net.tab.deleteReplace(n)
+				return unresponsive, nil
+			case pingPacket:
+				net.handlePing(n, pkt)
+				return contested, nil
+			default:
+				return net.handleQueryEvent(n, ev, pkt)
+			}
+		},
+	}
+
+	unresponsive = &nodeState{
+		name:     "unresponsive",
+		canQuery: true,
+		handle: func(net *Network, n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+			switch ev {
+			case pingPacket:
+				net.handlePing(n, pkt)
+				return known, nil
+			case pongPacket:
+				err := net.handleKnownPong(n, pkt)
+				return known, err
+			default:
+				return net.handleQueryEvent(n, ev, pkt)
+			}
+		},
+	}
+}
+
+// handle processes packets sent by n and events related to n.
+func (net *Network) handle(n *Node, ev nodeEvent, pkt *ingressPacket) error {
+	if pkt != nil {
+		if err := net.checkPacket(n, ev, pkt); err != nil {
+			return err
+		}
+		// Start the background expiration goroutine after the first
+		// successful communication. Subsequent calls have no effect if it
+		// is already running. We do this here instead of somewhere else
+		// so that the search for seed nodes also considers older nodes
+		// that would otherwise be removed by the expirer.
+		if net.db != nil {
+			net.db.ensureExpirer()
+		}
+	}
+	if n.state == nil {
+		n.state = unknown //???
+	}
+	next, err := n.state.handle(net, n, ev, pkt)
+	net.transition(n, next)
+	return err
+}
+
+func (net *Network) checkPacket(n *Node, ev nodeEvent, pkt *ingressPacket) error {
+	// Replay prevention checks.
+	switch ev {
+	case pingPacket, findnodeHashPacket, neighborsPacket:
+		// TODO: check date is > last date seen
+		// TODO: check ping version
+	case pongPacket:
+		if !bytes.Equal(pkt.data.(*pong).ReplyTok, n.pingEcho) {
+			// fmt.Println("pong reply token mismatch")
+			return fmt.Errorf("pong reply token mismatch")
+		}
+		n.pingEcho = nil
+	}
+	// Address validation.
+	// TODO: Ideally we would do the following:
+	//  - reject all packets with wrong address except ping.
+	//  - for ping with new address, transition to verifywait but keep the
+	//    previous node (with old address) around. if the new one reaches known,
+	//    swap it out.
+	return nil
+}
+
+func (net *Network) transition(n *Node, next *nodeState) {
+	if n.state != next {
+		n.state = next
+		if next.enter != nil {
+			next.enter(net, n)
+		}
+	}
+
+	// TODO: persist/unpersist node
+}
+
+func (net *Network) timedEvent(d time.Duration, n *Node, ev nodeEvent) {
+	timeout := timeoutEvent{ev, n}
+	net.timeoutTimers[timeout] = time.AfterFunc(d, func() {
+		select {
+		case net.timeout <- timeout:
+		case <-net.closed:
+		}
+	})
+}
+
+func (net *Network) abortTimedEvent(n *Node, ev nodeEvent) {
+	timer := net.timeoutTimers[timeoutEvent{ev, n}]
+	if timer != nil {
+		timer.Stop()
+		delete(net.timeoutTimers, timeoutEvent{ev, n})
+	}
+}
+
+func (net *Network) ping(n *Node, addr *net.UDPAddr) {
+	debugLog(fmt.Sprintf("ping(node = %x)", n.ID[:8]))
+	n.pingTopics = net.ticketStore.regTopicSet()
+	n.pingEcho = net.conn.sendPing(n, addr, n.pingTopics)
+	net.timedEvent(respTimeout, n, pongTimeout)
+}
+
+func (net *Network) handlePing(n *Node, pkt *ingressPacket) {
+	debugLog(fmt.Sprintf("handlePing(node = %x)", n.ID[:8]))
+	ping := pkt.data.(*ping)
+	n.TCP = ping.From.TCP
+	t := net.topictab.getTicket(n, ping.Topics)
+
+	pong := &pong{
+		To:         makeEndpoint(n.addr(), n.TCP), // TODO: maybe use known TCP port from DB
+		ReplyTok:   pkt.hash,
+		Expiration: uint64(time.Now().Add(expiration).Unix()),
+	}
+	ticketToPong(t, pong)
+	net.conn.send(n, pongPacket, pong)
+}
+
+func (net *Network) handleKnownPong(n *Node, pkt *ingressPacket) error {
+	debugLog(fmt.Sprintf("handleKnownPong(node = %x)", n.ID[:8]))
+	net.abortTimedEvent(n, pongTimeout)
+	now := mclock.Now()
+	ticket, err := pongToTicket(now, n.pingTopics, n, pkt)
+	if err == nil {
+		// fmt.Printf("(%x) ticket: %+v\n", net.tab.self.ID[:8], pkt.data)
+		net.ticketStore.addTicket(now, pkt.data.(*pong).ReplyTok, ticket)
+	} else {
+		debugLog(fmt.Sprintf(" error: %v", err))
+	}
+
+	n.pingEcho = nil
+	n.pingTopics = nil
+	return err
+}
+
+func (net *Network) handleQueryEvent(n *Node, ev nodeEvent, pkt *ingressPacket) (*nodeState, error) {
+	switch ev {
+	case findnodePacket:
+		target := crypto.Keccak256Hash(pkt.data.(*findnode).Target[:])
+		results := net.tab.closest(target, bucketSize).entries
+		net.conn.sendNeighbours(n, results)
+		return n.state, nil
+	case neighborsPacket:
+		err := net.handleNeighboursPacket(n, pkt.data.(*neighbors))
+		return n.state, err
+	case neighboursTimeout:
+		if n.pendingNeighbours != nil {
+			n.pendingNeighbours.reply <- nil
+			n.pendingNeighbours = nil
+		}
+		n.queryTimeouts++
+		if n.queryTimeouts > maxFindnodeFailures && n.state == known {
+			return contested, errors.New("too many timeouts")
+		}
+		return n.state, nil
+
+	// v5
+
+	case findnodeHashPacket:
+		results := net.tab.closest(pkt.data.(*findnodeHash).Target, bucketSize).entries
+		net.conn.sendNeighbours(n, results)
+		return n.state, nil
+	case topicRegisterPacket:
+		//fmt.Println("got topicRegisterPacket")
+		regdata := pkt.data.(*topicRegister)
+		pong, err := net.checkTopicRegister(regdata)
+		if err != nil {
+			//fmt.Println(err)
+			return n.state, fmt.Errorf("bad waiting ticket: %v", err)
+		}
+		net.topictab.useTicket(n, pong.TicketSerial, regdata.Topics, int(regdata.Idx), pong.Expiration, pong.WaitPeriods)
+		return n.state, nil
+	case topicQueryPacket:
+		// TODO: handle expiration
+		topic := pkt.data.(*topicQuery).Topic
+		results := net.topictab.getEntries(topic)
+		if _, ok := net.ticketStore.tickets[topic]; ok {
+			results = append(results, net.tab.self) // we're not registering in our own table but if we're advertising, return ourselves too
+		}
+		if len(results) > 10 {
+			results = results[:10]
+		}
+		var hash common.Hash
+		copy(hash[:], pkt.hash)
+		net.conn.sendTopicNodes(n, hash, results)
+		return n.state, nil
+	case topicNodesPacket:
+		p := pkt.data.(*topicNodes)
+		if net.ticketStore.gotTopicNodes(n, p.Echo, p.Nodes) {
+			n.queryTimeouts++
+			if n.queryTimeouts > maxFindnodeFailures && n.state == known {
+				return contested, errors.New("too many timeouts")
+			}
+		}
+		return n.state, nil
+
+	default:
+		return n.state, errInvalidEvent
+	}
+}
+
+func (net *Network) checkTopicRegister(data *topicRegister) (*pong, error) {
+	var pongpkt ingressPacket
+	if err := decodePacket(data.Pong, &pongpkt); err != nil {
+		return nil, err
+	}
+	if pongpkt.ev != pongPacket {
+		return nil, errors.New("is not pong packet")
+	}
+	if pongpkt.remoteID != net.tab.self.ID {
+		return nil, errors.New("not signed by us")
+	}
+	// check that we previously authorised all topics
+	// that the other side is trying to register.
+	if rlpHash(data.Topics) != pongpkt.data.(*pong).TopicHash {
+		return nil, errors.New("topic hash mismatch")
+	}
+	if data.Idx < 0 || int(data.Idx) >= len(data.Topics) {
+		return nil, errors.New("topic index out of range")
+	}
+	return pongpkt.data.(*pong), nil
+}
+
+func rlpHash(x interface{}) (h common.Hash) {
+	hw := sha3.NewKeccak256()
+	rlp.Encode(hw, x)
+	hw.Sum(h[:0])
+	return h
+}
+
+func (net *Network) handleNeighboursPacket(n *Node, req *neighbors) error {
+	if n.pendingNeighbours == nil {
+		return errNoQuery
+	}
+	net.abortTimedEvent(n, neighboursTimeout)
+
+	nodes := make([]*Node, len(req.Nodes))
+	for i, rn := range req.Nodes {
+		nn, err := net.internNodeFromNeighbours(rn)
+		if err != nil {
+			glog.V(logger.Debug).Infof("invalid neighbour from %x: %v", n.ID[:8], err)
+			continue
+		}
+		nodes[i] = nn
+		// Start validation of query results immediately.
+		// This fills the table quickly.
+		// TODO: generates way too many packets, maybe do it via queue.
+		if nn.state == unknown {
+			net.transition(nn, verifyinit)
+		}
+	}
+	// TODO: don't ignore second packet
+	n.pendingNeighbours.reply <- nodes
+	n.pendingNeighbours = nil
+	// Now that this query is done, start the next one.
+	n.startNextQuery(net)
+	return nil
+}
diff --git a/p2p/discv5/net_test.go b/p2p/discv5/net_test.go
new file mode 100644
index 000000000..422daa33b
--- /dev/null
+++ b/p2p/discv5/net_test.go
@@ -0,0 +1,371 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"fmt"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+func TestNetwork_Lookup(t *testing.T) {
+	key, _ := crypto.GenerateKey()
+	network, err := newNetwork(lookupTestnet, key.PublicKey, nil, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	lookupTestnet.net = network
+	defer network.Close()
+
+	// lookup on empty table returns no nodes
+	// if results := network.Lookup(lookupTestnet.target, false); len(results) > 0 {
+	// 	t.Fatalf("lookup on empty table returned %d results: %#v", len(results), results)
+	// }
+	// seed table with initial node (otherwise lookup will terminate immediately)
+	seeds := []*Node{NewNode(lookupTestnet.dists[256][0], net.IP{}, 256, 999)}
+	if err := network.SetFallbackNodes(seeds); err != nil {
+		t.Fatal(err)
+	}
+	time.Sleep(3 * time.Second)
+
+	results := network.Lookup(lookupTestnet.target)
+	t.Logf("results:")
+	for _, e := range results {
+		t.Logf("  ld=%d, %x", logdist(lookupTestnet.targetSha, e.sha), e.sha[:])
+	}
+	if len(results) != bucketSize {
+		t.Errorf("wrong number of results: got %d, want %d", len(results), bucketSize)
+	}
+	if hasDuplicates(results) {
+		t.Errorf("result set contains duplicate entries")
+	}
+	if !sortedByDistanceTo(lookupTestnet.targetSha, results) {
+		t.Errorf("result set not sorted by distance to target")
+	}
+	// TODO: check result nodes are actually closest
+}
+
+// This is the test network for the Lookup test.
+// The nodes were obtained by running testnet.mine with a random NodeID as target.
+var lookupTestnet = &preminedTestnet{
+	target:    MustHexID("166aea4f556532c6d34e8b740e5d314af7e9ac0ca79833bd751d6b665f12dfd38ec563c363b32f02aef4a80b44fd3def94612d497b99cb5f17fd24de454927ec"),
+	targetSha: common.Hash{0x5c, 0x94, 0x4e, 0xe5, 0x1c, 0x5a, 0xe9, 0xf7, 0x2a, 0x95, 0xec, 0xcb, 0x8a, 0xed, 0x3, 0x74, 0xee, 0xcb, 0x51, 0x19, 0xd7, 0x20, 0xcb, 0xea, 0x68, 0x13, 0xe8, 0xe0, 0xd6, 0xad, 0x92, 0x61},
+	dists: [257][]NodeID{
+		240: []NodeID{
+			MustHexID("2001ad5e3e80c71b952161bc0186731cf5ffe942d24a79230a0555802296238e57ea7a32f5b6f18564eadc1c65389448481f8c9338df0a3dbd18f708cbc2cbcb"),
+			MustHexID("6ba3f4f57d084b6bf94cc4555b8c657e4a8ac7b7baf23c6874efc21dd1e4f56b7eb2721e07f5242d2f1d8381fc8cae535e860197c69236798ba1ad231b105794"),
+		},
+		244: []NodeID{
+			MustHexID("696ba1f0a9d55c59246f776600542a9e6432490f0cd78f8bb55a196918df2081a9b521c3c3ba48e465a75c10768807717f8f689b0b4adce00e1c75737552a178"),
+		},
+		246: []NodeID{
+			MustHexID("d6d32178bdc38416f46ffb8b3ec9e4cb2cfff8d04dd7e4311a70e403cb62b10be1b447311b60b4f9ee221a8131fc2cbd45b96dd80deba68a949d467241facfa8"),
+			MustHexID("3ea3d04a43a3dfb5ac11cffc2319248cf41b6279659393c2f55b8a0a5fc9d12581a9d97ef5d8ff9b5abf3321a290e8f63a4f785f450dc8a672aba3ba2ff4fdab"),
+			MustHexID("2fc897f05ae585553e5c014effd3078f84f37f9333afacffb109f00ca8e7a3373de810a3946be971cbccdfd40249f9fe7f322118ea459ac71acca85a1ef8b7f4"),
+		},
+		247: []NodeID{
+			MustHexID("3155e1427f85f10a5c9a7755877748041af1bcd8d474ec065eb33df57a97babf54bfd2103575fa829115d224c523596b401065a97f74010610fce76382c0bf32"),
+			MustHexID("312c55512422cf9b8a4097e9a6ad79402e87a15ae909a4bfefa22398f03d20951933beea1e4dfa6f968212385e829f04c2d314fc2d4e255e0d3bc08792b069db"),
+			MustHexID("38643200b172dcfef857492156971f0e6aa2c538d8b74010f8e140811d53b98c765dd2d96126051913f44582e8c199ad7c6d6819e9a56483f637feaac9448aac"),
+			MustHexID("8dcab8618c3253b558d459da53bd8fa68935a719aff8b811197101a4b2b47dd2d47295286fc00cc081bb542d760717d1bdd6bec2c37cd72eca367d6dd3b9df73"),
+			MustHexID("8b58c6073dd98bbad4e310b97186c8f822d3a5c7d57af40e2136e88e315afd115edb27d2d0685a908cfe5aa49d0debdda6e6e63972691d6bd8c5af2d771dd2a9"),
+			MustHexID("2cbb718b7dc682da19652e7d9eb4fefaf7b7147d82c1c2b6805edf77b85e29fde9f6da195741467ff2638dc62c8d3e014ea5686693c15ed0080b6de90354c137"),
+			MustHexID("e84027696d3f12f2de30a9311afea8fbd313c2360daff52bb5fc8c7094d5295758bec3134e4eef24e4cdf377b40da344993284628a7a346eba94f74160998feb"),
+			MustHexID("f1357a4f04f9d33753a57c0b65ba20a5d8777abbffd04e906014491c9103fb08590e45548d37aa4bd70965e2e81ddba94f31860348df01469eec8c1829200a68"),
+			MustHexID("4ab0a75941b12892369b4490a1928c8ca52a9ad6d3dffbd1d8c0b907bc200fe74c022d011ec39b64808a39c0ca41f1d3254386c3e7733e7044c44259486461b6"),
+			MustHexID("d45150a72dc74388773e68e03133a3b5f51447fe91837d566706b3c035ee4b56f160c878c6273394daee7f56cc398985269052f22f75a8057df2fe6172765354"),
+		},
+		248: []NodeID{
+			MustHexID("6aadfce366a189bab08ac84721567483202c86590642ea6d6a14f37ca78d82bdb6509eb7b8b2f6f63c78ae3ae1d8837c89509e41497d719b23ad53dd81574afa"),
+			MustHexID("a605ecfd6069a4cf4cf7f5840e5bc0ce10d23a3ac59e2aaa70c6afd5637359d2519b4524f56fc2ca180cdbebe54262f720ccaae8c1b28fd553c485675831624d"),
+			MustHexID("29701451cb9448ca33fc33680b44b840d815be90146eb521641efbffed0859c154e8892d3906eae9934bfacee72cd1d2fa9dd050fd18888eea49da155ab0efd2"),
+			MustHexID("3ed426322dee7572b08592e1e079f8b6c6b30e10e6243edd144a6a48fdbdb83df73a6e41b1143722cb82604f2203a32758610b5d9544f44a1a7921ba001528c1"),
+			MustHexID("b2e2a2b7fdd363572a3256e75435fab1da3b16f7891a8bd2015f30995dae665d7eabfd194d87d99d5df628b4bbc7b04e5b492c596422dd8272746c7a1b0b8e4f"),
+			MustHexID("0c69c9756162c593e85615b814ce57a2a8ca2df6c690b9c4e4602731b61e1531a3bbe3f7114271554427ffabea80ad8f36fa95a49fa77b675ae182c6ccac1728"),
+			MustHexID("8d28be21d5a97b0876442fa4f5e5387f5bf3faad0b6f13b8607b64d6e448c0991ca28dd7fe2f64eb8eadd7150bff5d5666aa6ed868b84c71311f4ba9a38569dd"),
+			MustHexID("2c677e1c64b9c9df6359348a7f5f33dc79e22f0177042486d125f8b6ca7f0dc756b1f672aceee5f1746bcff80aaf6f92a8dc0c9fbeb259b3fa0da060de5ab7e8"),
+			MustHexID("3994880f94a8678f0cd247a43f474a8af375d2a072128da1ad6cae84a244105ff85e94fc7d8496f639468de7ee998908a91c7e33ef7585fff92e984b210941a1"),
+			MustHexID("b45a9153c08d002a48090d15d61a7c7dad8c2af85d4ff5bd36ce23a9a11e0709bf8d56614c7b193bc028c16cbf7f20dfbcc751328b64a924995d47b41e452422"),
+			MustHexID("057ab3a9e53c7a84b0f3fc586117a525cdd18e313f52a67bf31798d48078e325abe5cfee3f6c2533230cb37d0549289d692a29dd400e899b8552d4b928f6f907"),
+			MustHexID("0ddf663d308791eb92e6bd88a2f8cb45e4f4f35bb16708a0e6ff7f1362aa6a73fedd0a1b1557fb3365e38e1b79d6918e2fae2788728b70c9ab6b51a3b94a4338"),
+			MustHexID("f637e07ff50cc1e3731735841c4798411059f2023abcf3885674f3e8032531b0edca50fd715df6feb489b6177c345374d64f4b07d257a7745de393a107b013a5"),
+			MustHexID("e24ec7c6eec094f63c7b3239f56d311ec5a3e45bc4e622a1095a65b95eea6fe13e29f3b6b7a2cbfe40906e3989f17ac834c3102dd0cadaaa26e16ee06d782b72"),
+			MustHexID("b76ea1a6fd6506ef6e3506a4f1f60ed6287fff8114af6141b2ff13e61242331b54082b023cfea5b3083354a4fb3f9eb8be01fb4a518f579e731a5d0707291a6b"),
+			MustHexID("9b53a37950ca8890ee349b325032d7b672cab7eced178d3060137b24ef6b92a43977922d5bdfb4a3409a2d80128e02f795f9dae6d7d99973ad0e23a2afb8442f"),
+		},
+		249: []NodeID{
+			MustHexID("675ae65567c3c72c50c73bc0fd4f61f202ea5f93346ca57b551de3411ccc614fad61cb9035493af47615311b9d44ee7a161972ee4d77c28fe1ec029d01434e6a"),
+			MustHexID("8eb81408389da88536ae5800392b16ef5109d7ea132c18e9a82928047ecdb502693f6e4a4cdd18b54296caf561db937185731456c456c98bfe7de0baf0eaa495"),
+			MustHexID("2adba8b1612a541771cb93a726a38a4b88e97b18eced2593eb7daf82f05a5321ca94a72cc780c306ff21e551a932fc2c6d791e4681907b5ceab7f084c3fa2944"),
+			MustHexID("b1b4bfbda514d9b8f35b1c28961da5d5216fe50548f4066f69af3b7666a3b2e06eac646735e963e5c8f8138a2fb95af15b13b23ff00c6986eccc0efaa8ee6fb4"),
+			MustHexID("d2139281b289ad0e4d7b4243c4364f5c51aac8b60f4806135de06b12b5b369c9e43a6eb494eab860d115c15c6fbb8c5a1b0e382972e0e460af395b8385363de7"),
+			MustHexID("4a693df4b8fc5bdc7cec342c3ed2e228d7c5b4ab7321ddaa6cccbeb45b05a9f1d95766b4002e6d4791c2deacb8a667aadea6a700da28a3eea810a30395701bbc"),
+			MustHexID("ab41611195ec3c62bb8cd762ee19fb182d194fd141f4a66780efbef4b07ce916246c022b841237a3a6b512a93431157edd221e854ed2a259b72e9c5351f44d0c"),
+			MustHexID("68e8e26099030d10c3c703ae7045c0a48061fb88058d853b3e67880014c449d4311014da99d617d3150a20f1a3da5e34bf0f14f1c51fe4dd9d58afd222823176"),
+			MustHexID("3fbcacf546fb129cd70fc48de3b593ba99d3c473798bc309292aca280320e0eacc04442c914cad5c4cf6950345ba79b0d51302df88285d4e83ee3fe41339eee7"),
+			MustHexID("1d4a623659f7c8f80b6c3939596afdf42e78f892f682c768ad36eb7bfba402dbf97aea3a268f3badd8fe7636be216edf3d67ee1e08789ebbc7be625056bd7109"),
+			MustHexID("a283c474ab09da02bbc96b16317241d0627646fcc427d1fe790b76a7bf1989ced90f92101a973047ae9940c92720dffbac8eff21df8cae468a50f72f9e159417"),
+			MustHexID("dbf7e5ad7f87c3dfecae65d87c3039e14ed0bdc56caf00ce81931073e2e16719d746295512ff7937a15c3b03603e7c41a4f9df94fcd37bb200dd8f332767e9cb"),
+			MustHexID("caaa070a26692f64fc77f30d7b5ae980d419b4393a0f442b1c821ef58c0862898b0d22f74a4f8c5d83069493e3ec0b92f17dc1fe6e4cd437c1ec25039e7ce839"),
+			MustHexID("874cc8d1213beb65c4e0e1de38ef5d8165235893ac74ab5ea937c885eaab25c8d79dad0456e9fd3e9450626cac7e107b004478fb59842f067857f39a47cee695"),
+			MustHexID("d94193f236105010972f5df1b7818b55846592a0445b9cdc4eaed811b8c4c0f7c27dc8cc9837a4774656d6b34682d6d329d42b6ebb55da1d475c2474dc3dfdf4"),
+			MustHexID("edd9af6aded4094e9785637c28fccbd3980cbe28e2eb9a411048a23c2ace4bd6b0b7088a7817997b49a3dd05fc6929ca6c7abbb69438dbdabe65e971d2a794b2"),
+		},
+		250: []NodeID{
+			MustHexID("53a5bd1215d4ab709ae8fdc2ced50bba320bced78bd9c5dc92947fb402250c914891786db0978c898c058493f86fc68b1c5de8a5cb36336150ac7a88655b6c39"),
+			MustHexID("b7f79e3ab59f79262623c9ccefc8f01d682323aee56ffbe295437487e9d5acaf556a9c92e1f1c6a9601f2b9eb6b027ae1aeaebac71d61b9b78e88676efd3e1a3"),
+			MustHexID("d374bf7e8d7ffff69cc00bebff38ef5bc1dcb0a8d51c1a3d70e61ac6b2e2d6617109254b0ac224354dfbf79009fe4239e09020c483cc60c071e00b9238684f30"),
+			MustHexID("1e1eac1c9add703eb252eb991594f8f5a173255d526a855fab24ae57dc277e055bc3c7a7ae0b45d437c4f47a72d97eb7b126f2ba344ba6c0e14b2c6f27d4b1e6"),
+			MustHexID("ae28953f63d4bc4e706712a59319c111f5ff8f312584f65d7436b4cd3d14b217b958f8486bad666b4481fe879019fb1f767cf15b3e3e2711efc33b56d460448a"),
+			MustHexID("934bb1edf9c7a318b82306aca67feb3d6b434421fa275d694f0b4927afd8b1d3935b727fd4ff6e3d012e0c82f1824385174e8c6450ade59c2a43281a4b3446b6"),
+			MustHexID("9eef3f28f70ce19637519a0916555bf76d26de31312ac656cf9d3e379899ea44e4dd7ffcce923b4f3563f8a00489a34bd6936db0cbb4c959d32c49f017e07d05"),
+			MustHexID("82200872e8f871c48f1fad13daec6478298099b591bb3dbc4ef6890aa28ebee5860d07d70be62f4c0af85085a90ae8179ee8f937cf37915c67ea73e704b03ee7"),
+			MustHexID("6c75a5834a08476b7fc37ff3dc2011dc3ea3b36524bad7a6d319b18878fad813c0ba76d1f4555cacd3890c865438c21f0e0aed1f80e0a157e642124c69f43a11"),
+			MustHexID("995b873742206cb02b736e73a88580c2aacb0bd4a3c97a647b647bcab3f5e03c0e0736520a8b3600da09edf4248991fb01091ec7ff3ec7cdc8a1beae011e7aae"),
+			MustHexID("c773a056594b5cdef2e850d30891ff0e927c3b1b9c35cd8e8d53a1017001e237468e1ece3ae33d612ca3e6abb0a9169aa352e9dcda358e5af2ad982b577447db"),
+			MustHexID("2b46a5f6923f475c6be99ec6d134437a6d11f6bb4b4ac6bcd94572fa1092639d1c08aeefcb51f0912f0a060f71d4f38ee4da70ecc16010b05dd4a674aab14c3a"),
+			MustHexID("af6ab501366debbaa0d22e20e9688f32ef6b3b644440580fd78de4fe0e99e2a16eb5636bbae0d1c259df8ddda77b35b9a35cbc36137473e9c68fbc9d203ba842"),
+			MustHexID("c9f6f2dd1a941926f03f770695bda289859e85fabaf94baaae20b93e5015dc014ba41150176a36a1884adb52f405194693e63b0c464a6891cc9cc1c80d450326"),
+			MustHexID("5b116f0751526868a909b61a30b0c5282c37df6925cc03ddea556ef0d0602a9595fd6c14d371f8ed7d45d89918a032dcd22be4342a8793d88fdbeb3ca3d75bd7"),
+			MustHexID("50f3222fb6b82481c7c813b2172e1daea43e2710a443b9c2a57a12bd160dd37e20f87aa968c82ad639af6972185609d47036c0d93b4b7269b74ebd7073221c10"),
+		},
+		251: []NodeID{
+			MustHexID("9b8f702a62d1bee67bedfeb102eca7f37fa1713e310f0d6651cc0c33ea7c5477575289ccd463e5a2574a00a676a1fdce05658ba447bb9d2827f0ba47b947e894"),
+			MustHexID("b97532eb83054ed054b4abdf413bb30c00e4205545c93521554dbe77faa3cfaa5bd31ef466a107b0b34a71ec97214c0c83919720142cddac93aa7a3e928d4708"),
+			MustHexID("2f7a5e952bfb67f2f90b8441b5fadc9ee13b1dcde3afeeb3dd64bf937f86663cc5c55d1fa83952b5422763c7df1b7f2794b751c6be316ebc0beb4942e65ab8c1"),
+			MustHexID("42c7483781727051a0b3660f14faf39e0d33de5e643702ae933837d036508ab856ce7eec8ec89c4929a4901256e5233a3d847d5d4893f91bcf21835a9a880fee"),
+			MustHexID("873bae27bf1dc854408fba94046a53ab0c965cebe1e4e12290806fc62b88deb1f4a47f9e18f78fc0e7913a0c6e42ac4d0fc3a20cea6bc65f0c8a0ca90b67521e"),
+			MustHexID("a7e3a370bbd761d413f8d209e85886f68bf73d5c3089b2dc6fa42aab1ecb5162635497eed95dee2417f3c9c74a3e76319625c48ead2e963c7de877cd4551f347"),
+			MustHexID("528597534776a40df2addaaea15b6ff832ce36b9748a265768368f657e76d58569d9f30dbb91e91cf0ae7efe8f402f17aa0ae15f5c55051ba03ba830287f4c42"),
+			MustHexID("461d8bd4f13c3c09031fdb84f104ed737a52f630261463ce0bdb5704259bab4b737dda688285b8444dbecaecad7f50f835190b38684ced5e90c54219e5adf1bc"),
+			MustHexID("6ec50c0be3fd232737090fc0111caaf0bb6b18f72be453428087a11a97fd6b52db0344acbf789a689bd4f5f50f79017ea784f8fd6fe723ad6ae675b9e3b13e21"),
+			MustHexID("12fc5e2f77a83fdcc727b79d8ae7fe6a516881138d3011847ee136b400fed7cfba1f53fd7a9730253c7aa4f39abeacd04f138417ba7fcb0f36cccc3514e0dab6"),
+			MustHexID("4fdbe75914ccd0bce02101606a1ccf3657ec963e3b3c20239d5fec87673fe446d649b4f15f1fe1a40e6cfbd446dda2d31d40bb602b1093b8fcd5f139ba0eb46a"),
+			MustHexID("3753668a0f6281e425ea69b52cb2d17ab97afbe6eb84cf5d25425bc5e53009388857640668fadd7c110721e6047c9697803bd8a6487b43bb343bfa32ebf24039"),
+			MustHexID("2e81b16346637dec4410fd88e527346145b9c0a849dbf2628049ac7dae016c8f4305649d5659ec77f1e8a0fac0db457b6080547226f06283598e3740ad94849a"),
+			MustHexID("802c3cc27f91c89213223d758f8d2ecd41135b357b6d698f24d811cdf113033a81c38e0bdff574a5c005b00a8c193dc2531f8c1fa05fa60acf0ab6f2858af09f"),
+			MustHexID("fcc9a2e1ac3667026ff16192876d1813bb75abdbf39b929a92863012fe8b1d890badea7a0de36274d5c1eb1e8f975785532c50d80fd44b1a4b692f437303393f"),
+			MustHexID("6d8b3efb461151dd4f6de809b62726f5b89e9b38e9ba1391967f61cde844f7528fecf821b74049207cee5a527096b31f3ad623928cd3ce51d926fa345a6b2951"),
+		},
+		252: []NodeID{
+			MustHexID("f1ae93157cc48c2075dd5868fbf523e79e06caf4b8198f352f6e526680b78ff4227263de92612f7d63472bd09367bb92a636fff16fe46ccf41614f7a72495c2a"),
+			MustHexID("587f482d111b239c27c0cb89b51dd5d574db8efd8de14a2e6a1400c54d4567e77c65f89c1da52841212080b91604104768350276b6682f2f961cdaf4039581c7"),
+			MustHexID("e3f88274d35cefdaabdf205afe0e80e936cc982b8e3e47a84ce664c413b29016a4fb4f3a3ebae0a2f79671f8323661ed462bf4390af94c424dc8ace0c301b90f"),
+			MustHexID("0ddc736077da9a12ba410dc5ea63cbcbe7659dd08596485b2bff3435221f82c10d263efd9af938e128464be64a178b7cd22e19f400d5802f4c9df54bf89f2619"),
+			MustHexID("784aa34d833c6ce63fcc1279630113c3272e82c4ae8c126c5a52a88ac461b6baeed4244e607b05dc14e5b2f41c70a273c3804dea237f14f7a1e546f6d1309d14"),
+			MustHexID("f253a2c354ee0e27cfcae786d726753d4ad24be6516b279a936195a487de4a59dbc296accf20463749ff55293263ed8c1b6365eecb248d44e75e9741c0d18205"),
+			MustHexID("a1910b80357b3ad9b4593e0628922939614dc9056a5fbf477279c8b2c1d0b4b31d89a0c09d0d41f795271d14d3360ef08a3f821e65e7e1f56c07a36afe49c7c5"),
+			MustHexID("f1168552c2efe541160f0909b0b4a9d6aeedcf595cdf0e9b165c97e3e197471a1ee6320e93389edfba28af6eaf10de98597ad56e7ab1b504ed762451996c3b98"),
+			MustHexID("b0c8e5d2c8634a7930e1a6fd082e448c6cf9d2d8b7293558b59238815a4df926c286bf297d2049f14e8296a6eb3256af614ec1812c4f2bbe807673b58bf14c8c"),
+			MustHexID("0fb346076396a38badc342df3679b55bd7f40a609ab103411fe45082c01f12ea016729e95914b2b5540e987ff5c9b133e85862648e7f36abdfd23100d248d234"),
+			MustHexID("f736e0cc83417feaa280d9483f5d4d72d1b036cd0c6d9cbdeb8ac35ceb2604780de46dddaa32a378474e1d5ccdf79b373331c30c7911ade2ae32f98832e5de1f"),
+			MustHexID("8b02991457602f42b38b342d3f2259ae4100c354b3843885f7e4e07bd644f64dab94bb7f38a3915f8b7f11d8e3f81c28e07a0078cf79d7397e38a7b7e0c857e2"),
+			MustHexID("9221d9f04a8a184993d12baa91116692bb685f887671302999d69300ad103eb2d2c75a09d8979404c6dd28f12362f58a1a43619c493d9108fd47588a23ce5824"),
+			MustHexID("652797801744dada833fff207d67484742eea6835d695925f3e618d71b68ec3c65bdd85b4302b2cdcb835ad3f94fd00d8da07e570b41bc0d2bcf69a8de1b3284"),
+			MustHexID("d84f06fe64debc4cd0625e36d19b99014b6218375262cc2209202bdbafd7dffcc4e34ce6398e182e02fd8faeed622c3e175545864902dfd3d1ac57647cddf4c6"),
+			MustHexID("d0ed87b294f38f1d741eb601020eeec30ac16331d05880fe27868f1e454446de367d7457b41c79e202eaf9525b029e4f1d7e17d85a55f83a557c005c68d7328a"),
+		},
+		253: []NodeID{
+			MustHexID("ad4485e386e3cc7c7310366a7c38fb810b8896c0d52e55944bfd320ca294e7912d6c53c0a0cf85e7ce226e92491d60430e86f8f15cda0161ed71893fb4a9e3a1"),
+			MustHexID("36d0e7e5b7734f98c6183eeeb8ac5130a85e910a925311a19c4941b1290f945d4fc3996b12ef4966960b6fa0fb29b1604f83a0f81bd5fd6398d2e1a22e46af0c"),
+			MustHexID("7d307d8acb4a561afa23bdf0bd945d35c90245e26345ec3a1f9f7df354222a7cdcb81339c9ed6744526c27a1a0c8d10857e98df942fa433602facac71ac68a31"),
+			MustHexID("d97bf55f88c83fae36232661af115d66ca600fc4bd6d1fb35ff9bb4dad674c02cf8c8d05f317525b5522250db58bb1ecafb7157392bf5aa61b178c61f098d995"),
+			MustHexID("7045d678f1f9eb7a4613764d17bd5698796494d0bf977b16f2dbc272b8a0f7858a60805c022fc3d1fe4f31c37e63cdaca0416c0d053ef48a815f8b19121605e0"),
+			MustHexID("14e1f21418d445748de2a95cd9a8c3b15b506f86a0acabd8af44bb968ce39885b19c8822af61b3dd58a34d1f265baec30e3ae56149dc7d2aa4a538f7319f69c8"),
+			MustHexID("b9453d78281b66a4eac95a1546017111eaaa5f92a65d0de10b1122940e92b319728a24edf4dec6acc412321b1c95266d39c7b3a5d265c629c3e49a65fb022c09"),
+			MustHexID("e8a49248419e3824a00d86af422f22f7366e2d4922b304b7169937616a01d9d6fa5abf5cc01061a352dc866f48e1fa2240dbb453d872b1d7be62bdfc1d5e248c"),
+			MustHexID("bebcff24b52362f30e0589ee573ce2d86f073d58d18e6852a592fa86ceb1a6c9b96d7fb9ec7ed1ed98a51b6743039e780279f6bb49d0a04327ac7a182d9a56f6"),
+			MustHexID("d0835e5a4291db249b8d2fca9f503049988180c7d247bedaa2cf3a1bad0a76709360a85d4f9a1423b2cbc82bb4d94b47c0cde20afc430224834c49fe312a9ae3"),
+			MustHexID("6b087fe2a2da5e4f0b0f4777598a4a7fb66bf77dbd5bfc44e8a7eaa432ab585a6e226891f56a7d4f5ed11a7c57b90f1661bba1059590ca4267a35801c2802913"),
+			MustHexID("d901e5bde52d1a0f4ddf010a686a53974cdae4ebe5c6551b3c37d6b6d635d38d5b0e5f80bc0186a2c7809dbf3a42870dd09643e68d32db896c6da8ba734579e7"),
+			MustHexID("96419fb80efae4b674402bb969ebaab86c1274f29a83a311e24516d36cdf148fe21754d46c97688cdd7468f24c08b13e4727c29263393638a3b37b99ff60ebca"),
+			MustHexID("7b9c1889ae916a5d5abcdfb0aaedcc9c6f9eb1c1a4f68d0c2d034fe79ac610ce917c3abc670744150fa891bfcd8ab14fed6983fca964de920aa393fa7b326748"),
+			MustHexID("7a369b2b8962cc4c65900be046482fbf7c14f98a135bbbae25152c82ad168fb2097b3d1429197cf46d3ce9fdeb64808f908a489cc6019725db040060fdfe5405"),
+			MustHexID("47bcae48288da5ecc7f5058dfa07cf14d89d06d6e449cb946e237aa6652ea050d9f5a24a65efdc0013ccf232bf88670979eddef249b054f63f38da9d7796dbd8"),
+		},
+		254: []NodeID{
+			MustHexID("099739d7abc8abd38ecc7a816c521a1168a4dbd359fa7212a5123ab583ffa1cf485a5fed219575d6475dbcdd541638b2d3631a6c7fce7474e7fe3cba1d4d5853"),
+			MustHexID("c2b01603b088a7182d0cf7ef29fb2b04c70acb320fccf78526bf9472e10c74ee70b3fcfa6f4b11d167bd7d3bc4d936b660f2c9bff934793d97cb21750e7c3d31"),
+			MustHexID("20e4d8f45f2f863e94b45548c1ef22a11f7d36f263e4f8623761e05a64c4572379b000a52211751e2561b0f14f4fc92dd4130410c8ccc71eb4f0e95a700d4ca9"),
+			MustHexID("27f4a16cc085e72d86e25c98bd2eca173eaaee7565c78ec5a52e9e12b2211f35de81b5b45e9195de2ebfe29106742c59112b951a04eb7ae48822911fc1f9389e"),
+			MustHexID("55db5ee7d98e7f0b1c3b9d5be6f2bc619a1b86c3cdd513160ad4dcf267037a5fffad527ac15d50aeb32c59c13d1d4c1e567ebbf4de0d25236130c8361f9aac63"),
+			MustHexID("883df308b0130fc928a8559fe50667a0fff80493bc09685d18213b2db241a3ad11310ed86b0ef662b3ce21fc3d9aa7f3fc24b8d9afe17c7407e9afd3345ae548"),
+			MustHexID("c7af968cc9bc8200c3ee1a387405f7563be1dce6710a3439f42ea40657d0eae9d2b3c16c42d779605351fcdece4da637b9804e60ca08cfb89aec32c197beffa6"),
+			MustHexID("3e66f2b788e3ff1d04106b80597915cd7afa06c405a7ae026556b6e583dca8e05cfbab5039bb9a1b5d06083ffe8de5780b1775550e7218f5e98624bf7af9a0a8"),
+			MustHexID("4fc7f53764de3337fdaec0a711d35d3a923e72fa65025444d12230b3552ed43d9b2d1ad08ccb11f2d50c58809e6dd74dde910e195294fca3b47ae5a3967cc479"),
+			MustHexID("bafdfdcf6ccaa989436752fa97c77477b6baa7deb374b16c095492c529eb133e8e2f99e1977012b64767b9d34b2cf6d2048ed489bd822b5139b523f6a423167b"),
+			MustHexID("7f5d78008a4312fe059104ce80202c82b8915c2eb4411c6b812b16f7642e57c00f2c9425121f5cbac4257fe0b3e81ef5dea97ea2dbaa98f6a8b6fd4d1e5980bb"),
+			MustHexID("598c37fe78f922751a052f463aeb0cb0bc7f52b7c2a4cf2da72ec0931c7c32175d4165d0f8998f7320e87324ac3311c03f9382a5385c55f0407b7a66b2acd864"),
+			MustHexID("f758c4136e1c148777a7f3275a76e2db0b2b04066fd738554ec398c1c6cc9fb47e14a3b4c87bd47deaeab3ffd2110514c3855685a374794daff87b605b27ee2e"),
+			MustHexID("0307bb9e4fd865a49dcf1fe4333d1b944547db650ab580af0b33e53c4fef6c789531110fac801bbcbce21fc4d6f61b6d5b24abdf5b22e3030646d579f6dca9c2"),
+			MustHexID("82504b6eb49bb2c0f91a7006ce9cefdbaf6df38706198502c2e06601091fc9dc91e4f15db3410d45c6af355bc270b0f268d3dff560f956985c7332d4b10bd1ed"),
+			MustHexID("b39b5b677b45944ceebe76e76d1f051de2f2a0ec7b0d650da52135743e66a9a5dba45f638258f9a7545d9a790c7fe6d3fdf82c25425c7887323e45d27d06c057"),
+		},
+		255: []NodeID{
+			MustHexID("5c4d58d46e055dd1f093f81ee60a675e1f02f54da6206720adee4dccef9b67a31efc5c2a2949c31a04ee31beadc79aba10da31440a1f9ff2a24093c63c36d784"),
+			MustHexID("ea72161ffdd4b1e124c7b93b0684805f4c4b58d617ed498b37a145c670dbc2e04976f8785583d9c805ffbf343c31d492d79f841652bbbd01b61ed85640b23495"),
+			MustHexID("51caa1d93352d47a8e531692a3612adac1e8ac68d0a200d086c1c57ae1e1a91aa285ab242e8c52ef9d7afe374c9485b122ae815f1707b875569d0433c1c3ce85"),
+			MustHexID("c08397d5751b47bd3da044b908be0fb0e510d3149574dff7aeab33749b023bb171b5769990fe17469dbebc100bc150e798aeda426a2dcc766699a225fddd75c6"),
+			MustHexID("0222c1c194b749736e593f937fad67ee348ac57287a15c7e42877aa38a9b87732a408bca370f812efd0eedbff13e6d5b854bf3ba1dec431a796ed47f32552b09"),
+			MustHexID("03d859cd46ef02d9bfad5268461a6955426845eef4126de6be0fa4e8d7e0727ba2385b78f1a883a8239e95ebb814f2af8379632c7d5b100688eebc5841209582"),
+			MustHexID("64d5004b7e043c39ff0bd10cb20094c287721d5251715884c280a612b494b3e9e1c64ba6f67614994c7d969a0d0c0295d107d53fc225d47c44c4b82852d6f960"),
+			MustHexID("b0a5eefb2dab6f786670f35bf9641eefe6dd87fd3f1362bcab4aaa792903500ab23d88fae68411372e0813b057535a601d46e454323745a948017f6063a47b1f"),
+			MustHexID("0cc6df0a3433d448b5684d2a3ffa9d1a825388177a18f44ad0008c7bd7702f1ec0fc38b83506f7de689c3b6ecb552599927e29699eed6bb867ff08f80068b287"),
+			MustHexID("50772f7b8c03a4e153355fbbf79c8a80cf32af656ff0c7873c99911099d04a0dae0674706c357e0145ad017a0ade65e6052cb1b0d574fcd6f67da3eee0ace66b"),
+			MustHexID("1ae37829c9ef41f8b508b82259ebac76b1ed900d7a45c08b7970f25d2d48ddd1829e2f11423a18749940b6dab8598c6e416cef0efd47e46e51f29a0bc65b37cd"),
+			MustHexID("ba973cab31c2af091fc1644a93527d62b2394999e2b6ccbf158dd5ab9796a43d408786f1803ef4e29debfeb62fce2b6caa5ab2b24d1549c822a11c40c2856665"),
+			MustHexID("bc413ad270dd6ea25bddba78f3298b03b8ba6f8608ac03d06007d4116fa78ef5a0cfe8c80155089382fc7a193243ee5500082660cb5d7793f60f2d7d18650964"),
+			MustHexID("5a6a9ef07634d9eec3baa87c997b529b92652afa11473dfee41ef7037d5c06e0ddb9fe842364462d79dd31cff8a59a1b8d5bc2b810dea1d4cbbd3beb80ecec83"),
+			MustHexID("f492c6ee2696d5f682f7f537757e52744c2ae560f1090a07024609e903d334e9e174fc01609c5a229ddbcac36c9d21adaf6457dab38a25bfd44f2f0ee4277998"),
+			MustHexID("459e4db99298cb0467a90acee6888b08bb857450deac11015cced5104853be5adce5b69c740968bc7f931495d671a70cad9f48546d7cd203357fe9af0e8d2164"),
+		},
+		256: []NodeID{
+			MustHexID("a8593af8a4aef7b806b5197612017951bac8845a1917ca9a6a15dd6086d608505144990b245785c4cd2d67a295701c7aac2aa18823fb0033987284b019656268"),
+			MustHexID("d2eebef914928c3aad77fc1b2a495f52d2294acf5edaa7d8a530b540f094b861a68fe8348a46a7c302f08ab609d85912a4968eacfea0740847b29421b4795d9e"),
+			MustHexID("b14bfcb31495f32b650b63cf7d08492e3e29071fdc73cf2da0da48d4b191a70ba1a65f42ad8c343206101f00f8a48e8db4b08bf3f622c0853e7323b250835b91"),
+			MustHexID("7feaee0d818c03eb30e4e0bf03ade0f3c21ca38e938a761aa1781cf70bda8cc5cd631a6cc53dd44f1d4a6d3e2dae6513c6c66ee50cb2f0e9ad6f7e319b309fd9"),
+			MustHexID("4ca3b657b139311db8d583c25dd5963005e46689e1317620496cc64129c7f3e52870820e0ec7941d28809311df6db8a2867bbd4f235b4248af24d7a9c22d1232"),
+			MustHexID("1181defb1d16851d42dd951d84424d6bd1479137f587fa184d5a8152be6b6b16ed08bcdb2c2ed8539bcde98c80c432875f9f724737c316a2bd385a39d3cab1d8"),
+			MustHexID("d9dd818769fa0c3ec9f553c759b92476f082817252a04a47dc1777740b1731d280058c66f982812f173a294acf4944a85ba08346e2de153ba3ba41ce8a62cb64"),
+			MustHexID("bd7c4f8a9e770aa915c771b15e107ca123d838762da0d3ffc53aa6b53e9cd076cffc534ec4d2e4c334c683f1f5ea72e0e123f6c261915ed5b58ac1b59f003d88"),
+			MustHexID("3dd5739c73649d510456a70e9d6b46a855864a4a3f744e088fd8c8da11b18e4c9b5f2d7da50b1c147b2bae5ca9609ae01f7a3cdea9dce34f80a91d29cd82f918"),
+			MustHexID("f0d7df1efc439b4bcc0b762118c1cfa99b2a6143a9f4b10e3c9465125f4c9fca4ab88a2504169bbcad65492cf2f50da9dd5d077c39574a944f94d8246529066b"),
+			MustHexID("dd598b9ba441448e5fb1a6ec6c5f5aa9605bad6e223297c729b1705d11d05f6bfd3d41988b694681ae69bb03b9a08bff4beab5596503d12a39bffb5cd6e94c7c"),
+			MustHexID("3fce284ac97e567aebae681b15b7a2b6df9d873945536335883e4bbc26460c064370537f323fd1ada828ea43154992d14ac0cec0940a2bd2a3f42ec156d60c83"),
+			MustHexID("7c8dfa8c1311cb14fb29a8ac11bca23ecc115e56d9fcf7b7ac1db9066aa4eb39f8b1dabf46e192a65be95ebfb4e839b5ab4533fef414921825e996b210dd53bd"),
+			MustHexID("cafa6934f82120456620573d7f801390ed5e16ed619613a37e409e44ab355ef755e83565a913b48a9466db786f8d4fbd590bfec474c2524d4a2608d4eafd6abd"),
+			MustHexID("9d16600d0dd310d77045769fed2cb427f32db88cd57d86e49390c2ba8a9698cfa856f775be2013237226e7bf47b248871cf865d23015937d1edeb20db5e3e760"),
+			MustHexID("17be6b6ba54199b1d80eff866d348ea11d8a4b341d63ad9a6681d3ef8a43853ac564d153eb2a8737f0afc9ab320f6f95c55aa11aaa13bbb1ff422fd16bdf8188"),
+		},
+	},
+}
+
+type preminedTestnet struct {
+	target    NodeID
+	targetSha common.Hash // sha3(target)
+	dists     [hashBits + 1][]NodeID
+	net       *Network
+}
+
+func (tn *preminedTestnet) sendFindnode(to *Node, target NodeID) {
+	panic("sendFindnode called")
+}
+
+func (tn *preminedTestnet) sendFindnodeHash(to *Node, target common.Hash) {
+	// current log distance is encoded in port number
+	// fmt.Println("findnode query at dist", toaddr.Port)
+	if to.UDP == 0 {
+		panic("query to node at distance 0")
+	}
+	next := to.UDP - 1
+	var result []rpcNode
+	for i, id := range tn.dists[to.UDP] {
+		result = append(result, nodeToRPC(NewNode(id, net.ParseIP("127.0.0.1"), next, uint16(i)+1)))
+	}
+	injectResponse(tn.net, to, neighborsPacket, &neighbors{Nodes: result})
+}
+
+func (tn *preminedTestnet) sendPing(to *Node, addr *net.UDPAddr, topics []Topic) []byte {
+	injectResponse(tn.net, to, pongPacket, &pong{ReplyTok: []byte{1}})
+	return []byte{1}
+}
+
+func (tn *preminedTestnet) send(to *Node, ptype nodeEvent, data interface{}) (hash []byte) {
+	switch ptype {
+	case pingPacket:
+		injectResponse(tn.net, to, pongPacket, &pong{ReplyTok: []byte{1}})
+	case pongPacket:
+		// ignored
+	case findnodeHashPacket:
+		// current log distance is encoded in port number
+		// fmt.Println("findnode query at dist", toaddr.Port)
+		if to.UDP == 0 {
+			panic("query to node at distance 0")
+		}
+		next := to.UDP - 1
+		var result []rpcNode
+		for i, id := range tn.dists[to.UDP] {
+			result = append(result, nodeToRPC(NewNode(id, net.ParseIP("127.0.0.1"), next, uint16(i)+1)))
+		}
+		injectResponse(tn.net, to, neighborsPacket, &neighbors{Nodes: result})
+	default:
+		panic("send(" + ptype.String() + ")")
+	}
+	return []byte{2}
+}
+
+func (tn *preminedTestnet) sendNeighbours(to *Node, nodes []*Node) {
+	panic("sendNeighbours called")
+}
+
+func (tn *preminedTestnet) sendTopicQuery(to *Node, topic Topic) {
+	panic("sendTopicQuery called")
+}
+
+func (tn *preminedTestnet) sendTopicNodes(to *Node, queryHash common.Hash, nodes []*Node) {
+	panic("sendTopicNodes called")
+}
+
+func (tn *preminedTestnet) sendTopicRegister(to *Node, topics []Topic, idx int, pong []byte) {
+	panic("sendTopicRegister called")
+}
+
+func (*preminedTestnet) Close()                  {}
+func (*preminedTestnet) localAddr() *net.UDPAddr { return new(net.UDPAddr) }
+
+// mine generates a testnet struct literal with nodes at
+// various distances to the given target.
+func (n *preminedTestnet) mine(target NodeID) {
+	n.target = target
+	n.targetSha = crypto.Keccak256Hash(n.target[:])
+	found := 0
+	for found < bucketSize*10 {
+		k := newkey()
+		id := PubkeyID(&k.PublicKey)
+		sha := crypto.Keccak256Hash(id[:])
+		ld := logdist(n.targetSha, sha)
+		if len(n.dists[ld]) < bucketSize {
+			n.dists[ld] = append(n.dists[ld], id)
+			fmt.Println("found ID with ld", ld)
+			found++
+		}
+	}
+	fmt.Println("&preminedTestnet{")
+	fmt.Printf("	target: %#v,\n", n.target)
+	fmt.Printf("	targetSha: %#v,\n", n.targetSha)
+	fmt.Printf("	dists: [%d][]NodeID{\n", len(n.dists))
+	for ld, ns := range n.dists {
+		if len(ns) == 0 {
+			continue
+		}
+		fmt.Printf("		%d: []NodeID{\n", ld)
+		for _, n := range ns {
+			fmt.Printf("			MustHexID(\"%x\"),\n", n[:])
+		}
+		fmt.Println("		},")
+	}
+	fmt.Println("	},")
+	fmt.Println("}")
+}
+
+func injectResponse(net *Network, from *Node, ev nodeEvent, packet interface{}) {
+	go net.reqReadPacket(ingressPacket{remoteID: from.ID, remoteAddr: from.addr(), ev: ev, data: packet})
+}
diff --git a/p2p/discv5/node.go b/p2p/discv5/node.go
new file mode 100644
index 000000000..b6b6f149d
--- /dev/null
+++ b/p2p/discv5/node.go
@@ -0,0 +1,423 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"math/big"
+	"math/rand"
+	"net"
+	"net/url"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+// Node represents a host on the network.
+// The public fields of Node may not be modified.
+type Node struct {
+	IP       net.IP // len 4 for IPv4 or 16 for IPv6
+	UDP, TCP uint16 // port numbers
+	ID       NodeID // the node's public key
+
+	// Network-related fields are contained in nodeNetGuts.
+	// These fields are not supposed to be used off the
+	// Network.loop goroutine.
+	nodeNetGuts
+}
+
+// NewNode creates a new node. It is mostly meant to be used for
+// testing purposes.
+func NewNode(id NodeID, ip net.IP, udpPort, tcpPort uint16) *Node {
+	if ipv4 := ip.To4(); ipv4 != nil {
+		ip = ipv4
+	}
+	return &Node{
+		IP:          ip,
+		UDP:         udpPort,
+		TCP:         tcpPort,
+		ID:          id,
+		nodeNetGuts: nodeNetGuts{sha: crypto.Keccak256Hash(id[:])},
+	}
+}
+
+func (n *Node) addr() *net.UDPAddr {
+	return &net.UDPAddr{IP: n.IP, Port: int(n.UDP)}
+}
+
+func (n *Node) setAddr(a *net.UDPAddr) {
+	n.IP = a.IP
+	if ipv4 := a.IP.To4(); ipv4 != nil {
+		n.IP = ipv4
+	}
+	n.UDP = uint16(a.Port)
+}
+
+// compares the given address against the stored values.
+func (n *Node) addrEqual(a *net.UDPAddr) bool {
+	ip := a.IP
+	if ipv4 := a.IP.To4(); ipv4 != nil {
+		ip = ipv4
+	}
+	return n.UDP == uint16(a.Port) && bytes.Equal(n.IP, ip)
+}
+
+// Incomplete returns true for nodes with no IP address.
+func (n *Node) Incomplete() bool {
+	return n.IP == nil
+}
+
+// checks whether n is a valid complete node.
+func (n *Node) validateComplete() error {
+	if n.Incomplete() {
+		return errors.New("incomplete node")
+	}
+	if n.UDP == 0 {
+		return errors.New("missing UDP port")
+	}
+	if n.TCP == 0 {
+		return errors.New("missing TCP port")
+	}
+	if n.IP.IsMulticast() || n.IP.IsUnspecified() {
+		return errors.New("invalid IP (multicast/unspecified)")
+	}
+	_, err := n.ID.Pubkey() // validate the key (on curve, etc.)
+	return err
+}
+
+// The string representation of a Node is a URL.
+// Please see ParseNode for a description of the format.
+func (n *Node) String() string {
+	u := url.URL{Scheme: "enode"}
+	if n.Incomplete() {
+		u.Host = fmt.Sprintf("%x", n.ID[:])
+	} else {
+		addr := net.TCPAddr{IP: n.IP, Port: int(n.TCP)}
+		u.User = url.User(fmt.Sprintf("%x", n.ID[:]))
+		u.Host = addr.String()
+		if n.UDP != n.TCP {
+			u.RawQuery = "discport=" + strconv.Itoa(int(n.UDP))
+		}
+	}
+	return u.String()
+}
+
+var incompleteNodeURL = regexp.MustCompile("(?i)^(?:enode://)?([0-9a-f]+)$")
+
+// ParseNode parses a node designator.
+//
+// There are two basic forms of node designators
+//   - incomplete nodes, which only have the public key (node ID)
+//   - complete nodes, which contain the public key and IP/Port information
+//
+// For incomplete nodes, the designator must look like one of these
+//
+//    enode://<hex node id>
+//    <hex node id>
+//
+// For complete nodes, the node ID is encoded in the username portion
+// of the URL, separated from the host by an @ sign. The hostname can
+// only be given as an IP address, DNS domain names are not allowed.
+// The port in the host name section is the TCP listening port. If the
+// TCP and UDP (discovery) ports differ, the UDP port is specified as
+// query parameter "discport".
+//
+// In the following example, the node URL describes
+// a node with IP address 10.3.58.6, TCP listening port 30303
+// and UDP discovery port 30301.
+//
+//    enode://<hex node id>@10.3.58.6:30303?discport=30301
+func ParseNode(rawurl string) (*Node, error) {
+	if m := incompleteNodeURL.FindStringSubmatch(rawurl); m != nil {
+		id, err := HexID(m[1])
+		if err != nil {
+			return nil, fmt.Errorf("invalid node ID (%v)", err)
+		}
+		return NewNode(id, nil, 0, 0), nil
+	}
+	return parseComplete(rawurl)
+}
+
+func parseComplete(rawurl string) (*Node, error) {
+	var (
+		id               NodeID
+		ip               net.IP
+		tcpPort, udpPort uint64
+	)
+	u, err := url.Parse(rawurl)
+	if err != nil {
+		return nil, err
+	}
+	if u.Scheme != "enode" {
+		return nil, errors.New("invalid URL scheme, want \"enode\"")
+	}
+	// Parse the Node ID from the user portion.
+	if u.User == nil {
+		return nil, errors.New("does not contain node ID")
+	}
+	if id, err = HexID(u.User.String()); err != nil {
+		return nil, fmt.Errorf("invalid node ID (%v)", err)
+	}
+	// Parse the IP address.
+	host, port, err := net.SplitHostPort(u.Host)
+	if err != nil {
+		return nil, fmt.Errorf("invalid host: %v", err)
+	}
+	if ip = net.ParseIP(host); ip == nil {
+		return nil, errors.New("invalid IP address")
+	}
+	// Ensure the IP is 4 bytes long for IPv4 addresses.
+	if ipv4 := ip.To4(); ipv4 != nil {
+		ip = ipv4
+	}
+	// Parse the port numbers.
+	if tcpPort, err = strconv.ParseUint(port, 10, 16); err != nil {
+		return nil, errors.New("invalid port")
+	}
+	udpPort = tcpPort
+	qv := u.Query()
+	if qv.Get("discport") != "" {
+		udpPort, err = strconv.ParseUint(qv.Get("discport"), 10, 16)
+		if err != nil {
+			return nil, errors.New("invalid discport in query")
+		}
+	}
+	return NewNode(id, ip, uint16(udpPort), uint16(tcpPort)), nil
+}
+
+// MustParseNode parses a node URL. It panics if the URL is not valid.
+func MustParseNode(rawurl string) *Node {
+	n, err := ParseNode(rawurl)
+	if err != nil {
+		panic("invalid node URL: " + err.Error())
+	}
+	return n
+}
+
+// type nodeQueue []*Node
+//
+// // pushNew adds n to the end if it is not present.
+// func (nl *nodeList) appendNew(n *Node) {
+// 	for _, entry := range n {
+// 		if entry == n {
+// 			return
+// 		}
+// 	}
+// 	*nq = append(*nq, n)
+// }
+//
+// // popRandom removes a random node. Nodes closer to
+// // to the head of the beginning of the have a slightly higher probability.
+// func (nl *nodeList) popRandom() *Node {
+// 	ix := rand.Intn(len(*nq))
+// 	//TODO: probability as mentioned above.
+// 	nl.removeIndex(ix)
+// }
+//
+// func (nl *nodeList) removeIndex(i int) *Node {
+// 	slice = *nl
+// 	if len(*slice) <= i {
+// 		return nil
+// 	}
+// 	*nl = append(slice[:i], slice[i+1:]...)
+// }
+
+const nodeIDBits = 512
+
+// NodeID is a unique identifier for each node.
+// The node identifier is a marshaled elliptic curve public key.
+type NodeID [nodeIDBits / 8]byte
+
+// NodeID prints as a long hexadecimal number.
+func (n NodeID) String() string {
+	return fmt.Sprintf("%x", n[:])
+}
+
+// The Go syntax representation of a NodeID is a call to HexID.
+func (n NodeID) GoString() string {
+	return fmt.Sprintf("discover.HexID(\"%x\")", n[:])
+}
+
+// HexID converts a hex string to a NodeID.
+// The string may be prefixed with 0x.
+func HexID(in string) (NodeID, error) {
+	if strings.HasPrefix(in, "0x") {
+		in = in[2:]
+	}
+	var id NodeID
+	b, err := hex.DecodeString(in)
+	if err != nil {
+		return id, err
+	} else if len(b) != len(id) {
+		return id, fmt.Errorf("wrong length, want %d hex chars", len(id)*2)
+	}
+	copy(id[:], b)
+	return id, nil
+}
+
+// MustHexID converts a hex string to a NodeID.
+// It panics if the string is not a valid NodeID.
+func MustHexID(in string) NodeID {
+	id, err := HexID(in)
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
+// PubkeyID returns a marshaled representation of the given public key.
+func PubkeyID(pub *ecdsa.PublicKey) NodeID {
+	var id NodeID
+	pbytes := elliptic.Marshal(pub.Curve, pub.X, pub.Y)
+	if len(pbytes)-1 != len(id) {
+		panic(fmt.Errorf("need %d bit pubkey, got %d bits", (len(id)+1)*8, len(pbytes)))
+	}
+	copy(id[:], pbytes[1:])
+	return id
+}
+
+// Pubkey returns the public key represented by the node ID.
+// It returns an error if the ID is not a point on the curve.
+func (id NodeID) Pubkey() (*ecdsa.PublicKey, error) {
+	p := &ecdsa.PublicKey{Curve: S256(), X: new(big.Int), Y: new(big.Int)}
+	half := len(id) / 2
+	p.X.SetBytes(id[:half])
+	p.Y.SetBytes(id[half:])
+	if !p.Curve.IsOnCurve(p.X, p.Y) {
+		return nil, errors.New("id is invalid secp256k1 curve point")
+	}
+	return p, nil
+}
+
+func (id NodeID) mustPubkey() ecdsa.PublicKey {
+	pk, err := id.Pubkey()
+	if err != nil {
+		panic(err)
+	}
+	return *pk
+}
+
+// recoverNodeID computes the public key used to sign the
+// given hash from the signature.
+func recoverNodeID(hash, sig []byte) (id NodeID, err error) {
+	pubkey, err := crypto.Ecrecover(hash, sig)
+	if err != nil {
+		return id, err
+	}
+	if len(pubkey)-1 != len(id) {
+		return id, fmt.Errorf("recovered pubkey has %d bits, want %d bits", len(pubkey)*8, (len(id)+1)*8)
+	}
+	for i := range id {
+		id[i] = pubkey[i+1]
+	}
+	return id, nil
+}
+
+// distcmp compares the distances a->target and b->target.
+// Returns -1 if a is closer to target, 1 if b is closer to target
+// and 0 if they are equal.
+func distcmp(target, a, b common.Hash) int {
+	for i := range target {
+		da := a[i] ^ target[i]
+		db := b[i] ^ target[i]
+		if da > db {
+			return 1
+		} else if da < db {
+			return -1
+		}
+	}
+	return 0
+}
+
+// table of leading zero counts for bytes [0..255]
+var lzcount = [256]int{
+	8, 7, 6, 6, 5, 5, 5, 5,
+	4, 4, 4, 4, 4, 4, 4, 4,
+	3, 3, 3, 3, 3, 3, 3, 3,
+	3, 3, 3, 3, 3, 3, 3, 3,
+	2, 2, 2, 2, 2, 2, 2, 2,
+	2, 2, 2, 2, 2, 2, 2, 2,
+	2, 2, 2, 2, 2, 2, 2, 2,
+	2, 2, 2, 2, 2, 2, 2, 2,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	1, 1, 1, 1, 1, 1, 1, 1,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, 0, 0, 0,
+}
+
+// logdist returns the logarithmic distance between a and b, log2(a ^ b).
+func logdist(a, b common.Hash) int {
+	lz := 0
+	for i := range a {
+		x := a[i] ^ b[i]
+		if x == 0 {
+			lz += 8
+		} else {
+			lz += lzcount[x]
+			break
+		}
+	}
+	return len(a)*8 - lz
+}
+
+// hashAtDistance returns a random hash such that logdist(a, b) == n
+func hashAtDistance(a common.Hash, n int) (b common.Hash) {
+	if n == 0 {
+		return a
+	}
+	// flip bit at position n, fill the rest with random bits
+	b = a
+	pos := len(a) - n/8 - 1
+	bit := byte(0x01) << (byte(n%8) - 1)
+	if bit == 0 {
+		pos++
+		bit = 0x80
+	}
+	b[pos] = a[pos]&^bit | ^a[pos]&bit // TODO: randomize end bits
+	for i := pos + 1; i < len(a); i++ {
+		b[i] = byte(rand.Intn(255))
+	}
+	return b
+}
diff --git a/p2p/discv5/node_test.go b/p2p/discv5/node_test.go
new file mode 100644
index 000000000..ce4ad9e4d
--- /dev/null
+++ b/p2p/discv5/node_test.go
@@ -0,0 +1,305 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"fmt"
+	"math/big"
+	"math/rand"
+	"net"
+	"reflect"
+	"strings"
+	"testing"
+	"testing/quick"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+func ExampleNewNode() {
+	id := MustHexID("1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439")
+
+	// Complete nodes contain UDP and TCP endpoints:
+	n1 := NewNode(id, net.ParseIP("2001:db8:3c4d:15::abcd:ef12"), 52150, 30303)
+	fmt.Println("n1:", n1)
+	fmt.Println("n1.Incomplete() ->", n1.Incomplete())
+
+	// An incomplete node can be created by passing zero values
+	// for all parameters except id.
+	n2 := NewNode(id, nil, 0, 0)
+	fmt.Println("n2:", n2)
+	fmt.Println("n2.Incomplete() ->", n2.Incomplete())
+
+	// Output:
+	// n1: enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[2001:db8:3c4d:15::abcd:ef12]:30303?discport=52150
+	// n1.Incomplete() -> false
+	// n2: enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439
+	// n2.Incomplete() -> true
+}
+
+var parseNodeTests = []struct {
+	rawurl     string
+	wantError  string
+	wantResult *Node
+}{
+	{
+		rawurl:    "http://foobar",
+		wantError: `invalid URL scheme, want "enode"`,
+	},
+	{
+		rawurl:    "enode://01010101@123.124.125.126:3",
+		wantError: `invalid node ID (wrong length, want 128 hex chars)`,
+	},
+	// Complete nodes with IP address.
+	{
+		rawurl:    "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@hostname:3",
+		wantError: `invalid IP address`,
+	},
+	{
+		rawurl:    "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:foo",
+		wantError: `invalid port`,
+	},
+	{
+		rawurl:    "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:3?discport=foo",
+		wantError: `invalid discport in query`,
+	},
+	{
+		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150",
+		wantResult: NewNode(
+			MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{0x7f, 0x0, 0x0, 0x1},
+			52150,
+			52150,
+		),
+	},
+	{
+		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[::]:52150",
+		wantResult: NewNode(
+			MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.ParseIP("::"),
+			52150,
+			52150,
+		),
+	},
+	{
+		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[2001:db8:3c4d:15::abcd:ef12]:52150",
+		wantResult: NewNode(
+			MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.ParseIP("2001:db8:3c4d:15::abcd:ef12"),
+			52150,
+			52150,
+		),
+	},
+	{
+		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150?discport=22334",
+		wantResult: NewNode(
+			MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{0x7f, 0x0, 0x0, 0x1},
+			22334,
+			52150,
+		),
+	},
+	// Incomplete nodes with no address.
+	{
+		rawurl: "1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439",
+		wantResult: NewNode(
+			MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			nil, 0, 0,
+		),
+	},
+	{
+		rawurl: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439",
+		wantResult: NewNode(
+			MustHexID("0x1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			nil, 0, 0,
+		),
+	},
+	// Invalid URLs
+	{
+		rawurl:    "01010101",
+		wantError: `invalid node ID (wrong length, want 128 hex chars)`,
+	},
+	{
+		rawurl:    "enode://01010101",
+		wantError: `invalid node ID (wrong length, want 128 hex chars)`,
+	},
+	{
+		// This test checks that errors from url.Parse are handled.
+		rawurl:    "://foo",
+		wantError: `parse ://foo: missing protocol scheme`,
+	},
+}
+
+func TestParseNode(t *testing.T) {
+	for _, test := range parseNodeTests {
+		n, err := ParseNode(test.rawurl)
+		if test.wantError != "" {
+			if err == nil {
+				t.Errorf("test %q:\n  got nil error, expected %#q", test.rawurl, test.wantError)
+				continue
+			} else if err.Error() != test.wantError {
+				t.Errorf("test %q:\n  got error %#q, expected %#q", test.rawurl, err.Error(), test.wantError)
+				continue
+			}
+		} else {
+			if err != nil {
+				t.Errorf("test %q:\n  unexpected error: %v", test.rawurl, err)
+				continue
+			}
+			if !reflect.DeepEqual(n, test.wantResult) {
+				t.Errorf("test %q:\n  result mismatch:\ngot:  %#v, want: %#v", test.rawurl, n, test.wantResult)
+			}
+		}
+	}
+}
+
+func TestNodeString(t *testing.T) {
+	for i, test := range parseNodeTests {
+		if test.wantError == "" && strings.HasPrefix(test.rawurl, "enode://") {
+			str := test.wantResult.String()
+			if str != test.rawurl {
+				t.Errorf("test %d: Node.String() mismatch:\ngot:  %s\nwant: %s", i, str, test.rawurl)
+			}
+		}
+	}
+}
+
+func TestHexID(t *testing.T) {
+	ref := NodeID{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128, 106, 217, 182, 31, 165, 174, 1, 67, 7, 235, 220, 150, 66, 83, 173, 205, 159, 44, 10, 57, 42, 161, 26, 188}
+	id1 := MustHexID("0x000000000000000000000000000000000000000000000000000000000000000000000000000000806ad9b61fa5ae014307ebdc964253adcd9f2c0a392aa11abc")
+	id2 := MustHexID("000000000000000000000000000000000000000000000000000000000000000000000000000000806ad9b61fa5ae014307ebdc964253adcd9f2c0a392aa11abc")
+
+	if id1 != ref {
+		t.Errorf("wrong id1\ngot  %v\nwant %v", id1[:], ref[:])
+	}
+	if id2 != ref {
+		t.Errorf("wrong id2\ngot  %v\nwant %v", id2[:], ref[:])
+	}
+}
+
+func TestNodeID_recover(t *testing.T) {
+	prv := newkey()
+	hash := make([]byte, 32)
+	sig, err := crypto.Sign(hash, prv)
+	if err != nil {
+		t.Fatalf("signing error: %v", err)
+	}
+
+	pub := PubkeyID(&prv.PublicKey)
+	recpub, err := recoverNodeID(hash, sig)
+	if err != nil {
+		t.Fatalf("recovery error: %v", err)
+	}
+	if pub != recpub {
+		t.Errorf("recovered wrong pubkey:\ngot:  %v\nwant: %v", recpub, pub)
+	}
+
+	ecdsa, err := pub.Pubkey()
+	if err != nil {
+		t.Errorf("Pubkey error: %v", err)
+	}
+	if !reflect.DeepEqual(ecdsa, &prv.PublicKey) {
+		t.Errorf("Pubkey mismatch:\n  got:  %#v\n  want: %#v", ecdsa, &prv.PublicKey)
+	}
+}
+
+func TestNodeID_pubkeyBad(t *testing.T) {
+	ecdsa, err := NodeID{}.Pubkey()
+	if err == nil {
+		t.Error("expected error for zero ID")
+	}
+	if ecdsa != nil {
+		t.Error("expected nil result")
+	}
+}
+
+func TestNodeID_distcmp(t *testing.T) {
+	distcmpBig := func(target, a, b common.Hash) int {
+		tbig := new(big.Int).SetBytes(target[:])
+		abig := new(big.Int).SetBytes(a[:])
+		bbig := new(big.Int).SetBytes(b[:])
+		return new(big.Int).Xor(tbig, abig).Cmp(new(big.Int).Xor(tbig, bbig))
+	}
+	if err := quick.CheckEqual(distcmp, distcmpBig, quickcfg()); err != nil {
+		t.Error(err)
+	}
+}
+
+// the random tests is likely to miss the case where they're equal.
+func TestNodeID_distcmpEqual(t *testing.T) {
+	base := common.Hash{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
+	x := common.Hash{15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
+	if distcmp(base, x, x) != 0 {
+		t.Errorf("distcmp(base, x, x) != 0")
+	}
+}
+
+func TestNodeID_logdist(t *testing.T) {
+	logdistBig := func(a, b common.Hash) int {
+		abig, bbig := new(big.Int).SetBytes(a[:]), new(big.Int).SetBytes(b[:])
+		return new(big.Int).Xor(abig, bbig).BitLen()
+	}
+	if err := quick.CheckEqual(logdist, logdistBig, quickcfg()); err != nil {
+		t.Error(err)
+	}
+}
+
+// the random tests is likely to miss the case where they're equal.
+func TestNodeID_logdistEqual(t *testing.T) {
+	x := common.Hash{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
+	if logdist(x, x) != 0 {
+		t.Errorf("logdist(x, x) != 0")
+	}
+}
+
+func TestNodeID_hashAtDistance(t *testing.T) {
+	// we don't use quick.Check here because its output isn't
+	// very helpful when the test fails.
+	cfg := quickcfg()
+	for i := 0; i < cfg.MaxCount; i++ {
+		a := gen(common.Hash{}, cfg.Rand).(common.Hash)
+		dist := cfg.Rand.Intn(len(common.Hash{}) * 8)
+		result := hashAtDistance(a, dist)
+		actualdist := logdist(result, a)
+
+		if dist != actualdist {
+			t.Log("a:     ", a)
+			t.Log("result:", result)
+			t.Fatalf("#%d: distance of result is %d, want %d", i, actualdist, dist)
+		}
+	}
+}
+
+func quickcfg() *quick.Config {
+	return &quick.Config{
+		MaxCount: 5000,
+		Rand:     rand.New(rand.NewSource(time.Now().Unix())),
+	}
+}
+
+// TODO: The Generate method can be dropped when we require Go >= 1.5
+// because testing/quick learned to generate arrays in 1.5.
+
+func (NodeID) Generate(rand *rand.Rand, size int) reflect.Value {
+	var id NodeID
+	m := rand.Intn(len(id))
+	for i := len(id) - 1; i > m; i-- {
+		id[i] = byte(rand.Uint32())
+	}
+	return reflect.ValueOf(id)
+}
diff --git a/p2p/discv5/nodeevent_string.go b/p2p/discv5/nodeevent_string.go
new file mode 100644
index 000000000..fde9045c5
--- /dev/null
+++ b/p2p/discv5/nodeevent_string.go
@@ -0,0 +1,27 @@
+// Code generated by "stringer -type nodeEvent"; DO NOT EDIT
+
+package discv5
+
+import "fmt"
+
+const (
+	_nodeEvent_name_0 = "invalidEventpingPacketpongPacketfindnodePacketneighborsPacketfindnodeHashPackettopicRegisterPackettopicQueryPackettopicNodesPacket"
+	_nodeEvent_name_1 = "pongTimeoutpingTimeoutneighboursTimeout"
+)
+
+var (
+	_nodeEvent_index_0 = [...]uint8{0, 12, 22, 32, 46, 61, 79, 98, 114, 130}
+	_nodeEvent_index_1 = [...]uint8{0, 11, 22, 39}
+)
+
+func (i nodeEvent) String() string {
+	switch {
+	case 0 <= i && i <= 8:
+		return _nodeEvent_name_0[_nodeEvent_index_0[i]:_nodeEvent_index_0[i+1]]
+	case 265 <= i && i <= 267:
+		i -= 265
+		return _nodeEvent_name_1[_nodeEvent_index_1[i]:_nodeEvent_index_1[i+1]]
+	default:
+		return fmt.Sprintf("nodeEvent(%d)", i)
+	}
+}
diff --git a/p2p/discv5/ntp.go b/p2p/discv5/ntp.go
new file mode 100644
index 000000000..81c0e6336
--- /dev/null
+++ b/p2p/discv5/ntp.go
@@ -0,0 +1,127 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Contains the NTP time drift detection via the SNTP protocol:
+//   https://tools.ietf.org/html/rfc4330
+
+package discv5
+
+import (
+	"fmt"
+	"net"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+)
+
+const (
+	ntpPool   = "pool.ntp.org" // ntpPool is the NTP server to query for the current time
+	ntpChecks = 3              // Number of measurements to do against the NTP server
+)
+
+// durationSlice attaches the methods of sort.Interface to []time.Duration,
+// sorting in increasing order.
+type durationSlice []time.Duration
+
+func (s durationSlice) Len() int           { return len(s) }
+func (s durationSlice) Less(i, j int) bool { return s[i] < s[j] }
+func (s durationSlice) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// checkClockDrift queries an NTP server for clock drifts and warns the user if
+// one large enough is detected.
+func checkClockDrift() {
+	drift, err := sntpDrift(ntpChecks)
+	if err != nil {
+		return
+	}
+	if drift < -driftThreshold || drift > driftThreshold {
+		warning := fmt.Sprintf("System clock seems off by %v, which can prevent network connectivity", drift)
+		howtofix := fmt.Sprintf("Please enable network time synchronisation in system settings")
+		separator := strings.Repeat("-", len(warning))
+
+		glog.V(logger.Warn).Info(separator)
+		glog.V(logger.Warn).Info(warning)
+		glog.V(logger.Warn).Info(howtofix)
+		glog.V(logger.Warn).Info(separator)
+	} else {
+		glog.V(logger.Debug).Infof("Sanity NTP check reported %v drift, all ok", drift)
+	}
+}
+
+// sntpDrift does a naive time resolution against an NTP server and returns the
+// measured drift. This method uses the simple version of NTP. It's not precise
+// but should be fine for these purposes.
+//
+// Note, it executes two extra measurements compared to the number of requested
+// ones to be able to discard the two extremes as outliers.
+func sntpDrift(measurements int) (time.Duration, error) {
+	// Resolve the address of the NTP server
+	addr, err := net.ResolveUDPAddr("udp", ntpPool+":123")
+	if err != nil {
+		return 0, err
+	}
+	// Construct the time request (empty package with only 2 fields set):
+	//   Bits 3-5: Protocol version, 3
+	//   Bits 6-8: Mode of operation, client, 3
+	request := make([]byte, 48)
+	request[0] = 3<<3 | 3
+
+	// Execute each of the measurements
+	drifts := []time.Duration{}
+	for i := 0; i < measurements+2; i++ {
+		// Dial the NTP server and send the time retrieval request
+		conn, err := net.DialUDP("udp", nil, addr)
+		if err != nil {
+			return 0, err
+		}
+		defer conn.Close()
+
+		sent := time.Now()
+		if _, err = conn.Write(request); err != nil {
+			return 0, err
+		}
+		// Retrieve the reply and calculate the elapsed time
+		conn.SetDeadline(time.Now().Add(5 * time.Second))
+
+		reply := make([]byte, 48)
+		if _, err = conn.Read(reply); err != nil {
+			return 0, err
+		}
+		elapsed := time.Since(sent)
+
+		// Reconstruct the time from the reply data
+		sec := uint64(reply[43]) | uint64(reply[42])<<8 | uint64(reply[41])<<16 | uint64(reply[40])<<24
+		frac := uint64(reply[47]) | uint64(reply[46])<<8 | uint64(reply[45])<<16 | uint64(reply[44])<<24
+
+		nanosec := sec*1e9 + (frac*1e9)>>32
+
+		t := time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC).Add(time.Duration(nanosec)).Local()
+
+		// Calculate the drift based on an assumed answer time of RRT/2
+		drifts = append(drifts, sent.Sub(t)+elapsed/2)
+	}
+	// Calculate average drif (drop two extremities to avoid outliers)
+	sort.Sort(durationSlice(drifts))
+
+	drift := time.Duration(0)
+	for i := 1; i < len(drifts)-1; i++ {
+		drift += drifts[i]
+	}
+	return drift / time.Duration(measurements), nil
+}
diff --git a/p2p/discv5/sim_run_test.go b/p2p/discv5/sim_run_test.go
new file mode 100644
index 000000000..bded0cc02
--- /dev/null
+++ b/p2p/discv5/sim_run_test.go
@@ -0,0 +1,126 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func getnacl() (string, error) {
+	switch runtime.GOARCH {
+	case "amd64":
+		_, err := exec.LookPath("sel_ldr_x86_64")
+		return "amd64p32", err
+	case "i386":
+		_, err := exec.LookPath("sel_ldr_i386")
+		return "i386", err
+	default:
+		return "", errors.New("nacl is not supported on " + runtime.GOARCH)
+	}
+}
+
+// runWithPlaygroundTime executes the caller
+// in the NaCl sandbox with faketime enabled.
+//
+// This function must be called from a Test* function
+// and the caller must skip the actual test when isHost is true.
+func runWithPlaygroundTime(t *testing.T) (isHost bool) {
+	if runtime.GOOS == "nacl" {
+		return false
+	}
+
+	// Get the caller.
+	callerPC, _, _, ok := runtime.Caller(1)
+	if !ok {
+		panic("can't get caller")
+	}
+	callerFunc := runtime.FuncForPC(callerPC)
+	if callerFunc == nil {
+		panic("can't get caller")
+	}
+	callerName := callerFunc.Name()[strings.LastIndexByte(callerFunc.Name(), '.')+1:]
+	if !strings.HasPrefix(callerName, "Test") {
+		panic("must be called from witin a Test* function")
+	}
+	testPattern := "^" + callerName + "$"
+
+	// Unfortunately runtime.faketime (playground time mode) only works on NaCl. The NaCl
+	// SDK must be installed and linked into PATH for this to work.
+	arch, err := getnacl()
+	if err != nil {
+		t.Skip(err)
+	}
+
+	// Compile and run the calling test using NaCl.
+	// The extra tag ensures that the TestMain function in sim_main_test.go is used.
+	cmd := exec.Command("go", "test", "-v", "-tags", "faketime_simulation", "-timeout", "100h", "-run", testPattern, ".")
+	cmd.Env = append([]string{"GOOS=nacl", "GOARCH=" + arch}, os.Environ()...)
+	stdout, _ := cmd.StdoutPipe()
+	stderr, _ := cmd.StderrPipe()
+	go skipPlaygroundOutputHeaders(os.Stdout, stdout)
+	go skipPlaygroundOutputHeaders(os.Stderr, stderr)
+	if err := cmd.Run(); err != nil {
+		t.Error(err)
+	}
+
+	// Ensure that the test function doesn't run in the (non-NaCl) host process.
+	return true
+}
+
+func skipPlaygroundOutputHeaders(out io.Writer, in io.Reader) {
+	// Additional output can be printed without the headers
+	// before the NaCl binary starts running (e.g. compiler error messages).
+	bufin := bufio.NewReader(in)
+	output, err := bufin.ReadBytes(0)
+	output = bytes.TrimSuffix(output, []byte{0})
+	if len(output) > 0 {
+		out.Write(output)
+	}
+	if err != nil {
+		return
+	}
+	bufin.UnreadByte()
+
+	// Playback header: 0 0 P B <8-byte time> <4-byte data length>
+	head := make([]byte, 4+8+4)
+	for {
+		if _, err := io.ReadFull(bufin, head); err != nil {
+			if err != io.EOF {
+				fmt.Fprintln(out, "read error:", err)
+			}
+			return
+		}
+		if !bytes.HasPrefix(head, []byte{0x00, 0x00, 'P', 'B'}) {
+			fmt.Fprintf(out, "expected playback header, got %q\n", head)
+			io.Copy(out, bufin)
+			return
+		}
+		// Copy data until next header.
+		size := binary.BigEndian.Uint32(head[12:])
+		io.CopyN(out, bufin, int64(size))
+	}
+}
diff --git a/p2p/discv5/sim_test.go b/p2p/discv5/sim_test.go
new file mode 100644
index 000000000..2e232fbaa
--- /dev/null
+++ b/p2p/discv5/sim_test.go
@@ -0,0 +1,464 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"crypto/ecdsa"
+	"encoding/binary"
+	"fmt"
+	"math/rand"
+	"net"
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+// In this test, nodes try to randomly resolve each other.
+func TestSimRandomResolve(t *testing.T) {
+	t.Skip("boring")
+	if runWithPlaygroundTime(t) {
+		return
+	}
+
+	sim := newSimulation()
+	bootnode := sim.launchNode(false)
+
+	// A new node joins every 10s.
+	launcher := time.NewTicker(10 * time.Second)
+	go func() {
+		for range launcher.C {
+			net := sim.launchNode(false)
+			go randomResolves(t, sim, net)
+			if err := net.SetFallbackNodes([]*Node{bootnode.Self()}); err != nil {
+				panic(err)
+			}
+			fmt.Printf("launched @ %v: %x\n", time.Now(), net.Self().ID[:16])
+		}
+	}()
+
+	time.Sleep(3 * time.Hour)
+	launcher.Stop()
+	sim.shutdown()
+	sim.printStats()
+}
+
+func TestSimTopics(t *testing.T) {
+	t.Skip("NaCl test")
+	if runWithPlaygroundTime(t) {
+		return
+	}
+
+	// glog.SetV(6)
+	// glog.SetToStderr(true)
+
+	sim := newSimulation()
+	bootnode := sim.launchNode(false)
+
+	go func() {
+		nets := make([]*Network, 1024)
+		for i, _ := range nets {
+			net := sim.launchNode(false)
+			nets[i] = net
+			if err := net.SetFallbackNodes([]*Node{bootnode.Self()}); err != nil {
+				panic(err)
+			}
+			time.Sleep(time.Second * 5)
+		}
+
+		for i, net := range nets {
+			if i < 256 {
+				stop := make(chan struct{})
+				go net.RegisterTopic(testTopic, stop)
+				go func() {
+					//time.Sleep(time.Second * 36000)
+					time.Sleep(time.Second * 40000)
+					close(stop)
+				}()
+				time.Sleep(time.Millisecond * 100)
+			}
+			//			time.Sleep(time.Second * 10)
+			//time.Sleep(time.Second)
+			/*if i%500 == 499 {
+				time.Sleep(time.Second * 9501)
+			} else {
+				time.Sleep(time.Second)
+			}*/
+		}
+	}()
+
+	// A new node joins every 10s.
+	/*	launcher := time.NewTicker(5 * time.Second)
+		cnt := 0
+		var printNet *Network
+		go func() {
+			for range launcher.C {
+				cnt++
+				if cnt <= 1000 {
+					log := false //(cnt == 500)
+					net := sim.launchNode(log)
+					if log {
+						printNet = net
+					}
+					if cnt > 500 {
+						go net.RegisterTopic(testTopic, nil)
+					}
+					if err := net.SetFallbackNodes([]*Node{bootnode.Self()}); err != nil {
+						panic(err)
+					}
+				}
+				//fmt.Printf("launched @ %v: %x\n", time.Now(), net.Self().ID[:16])
+			}
+		}()
+	*/
+	time.Sleep(55000 * time.Second)
+	//launcher.Stop()
+	sim.shutdown()
+	//sim.printStats()
+	//printNet.log.printLogs()
+}
+
+/*func testHierarchicalTopics(i int) []Topic {
+	digits := strconv.FormatInt(int64(256+i/4), 4)
+	res := make([]Topic, 5)
+	for i, _ := range res {
+		res[i] = Topic("foo" + digits[1:i+1])
+	}
+	return res
+}*/
+
+func testHierarchicalTopics(i int) []Topic {
+	digits := strconv.FormatInt(int64(128+i/8), 2)
+	res := make([]Topic, 8)
+	for i, _ := range res {
+		res[i] = Topic("foo" + digits[1:i+1])
+	}
+	return res
+}
+
+func TestSimTopicHierarchy(t *testing.T) {
+	t.Skip("NaCl test")
+	if runWithPlaygroundTime(t) {
+		return
+	}
+
+	// glog.SetV(6)
+	// glog.SetToStderr(true)
+
+	sim := newSimulation()
+	bootnode := sim.launchNode(false)
+
+	go func() {
+		nets := make([]*Network, 1024)
+		for i, _ := range nets {
+			net := sim.launchNode(false)
+			nets[i] = net
+			if err := net.SetFallbackNodes([]*Node{bootnode.Self()}); err != nil {
+				panic(err)
+			}
+			time.Sleep(time.Second * 5)
+		}
+
+		stop := make(chan struct{})
+		for i, net := range nets {
+			//if i < 256 {
+			for _, topic := range testHierarchicalTopics(i)[:5] {
+				//fmt.Println("reg", topic)
+				go net.RegisterTopic(topic, stop)
+			}
+			time.Sleep(time.Millisecond * 100)
+			//}
+		}
+		time.Sleep(time.Second * 90000)
+		close(stop)
+	}()
+
+	time.Sleep(100000 * time.Second)
+	sim.shutdown()
+}
+
+func randomResolves(t *testing.T, s *simulation, net *Network) {
+	randtime := func() time.Duration {
+		return time.Duration(rand.Intn(50)+20) * time.Second
+	}
+	lookup := func(target NodeID) bool {
+		result := net.Resolve(target)
+		return result != nil && result.ID == target
+	}
+
+	timer := time.NewTimer(randtime())
+	for {
+		select {
+		case <-timer.C:
+			target := s.randomNode().Self().ID
+			if !lookup(target) {
+				t.Errorf("node %x: target %x not found", net.Self().ID[:8], target[:8])
+			}
+			timer.Reset(randtime())
+		case <-net.closed:
+			return
+		}
+	}
+}
+
+type simulation struct {
+	mu      sync.RWMutex
+	nodes   map[NodeID]*Network
+	nodectr uint32
+}
+
+func newSimulation() *simulation {
+	return &simulation{nodes: make(map[NodeID]*Network)}
+}
+
+func (s *simulation) shutdown() {
+	s.mu.RLock()
+	alive := make([]*Network, 0, len(s.nodes))
+	for _, n := range s.nodes {
+		alive = append(alive, n)
+	}
+	defer s.mu.RUnlock()
+
+	for _, n := range alive {
+		n.Close()
+	}
+}
+
+func (s *simulation) printStats() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	fmt.Println("node counter:", s.nodectr)
+	fmt.Println("alive nodes:", len(s.nodes))
+
+	// for _, n := range s.nodes {
+	// 	fmt.Printf("%x\n", n.tab.self.ID[:8])
+	// 	transport := n.conn.(*simTransport)
+	// 	fmt.Println("   joined:", transport.joinTime)
+	// 	fmt.Println("   sends:", transport.hashctr)
+	// 	fmt.Println("   table size:", n.tab.count)
+	// }
+
+	/*for _, n := range s.nodes {
+		fmt.Println()
+		fmt.Printf("*** Node %x\n", n.tab.self.ID[:8])
+		n.log.printLogs()
+	}*/
+
+}
+
+func (s *simulation) randomNode() *Network {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	n := rand.Intn(len(s.nodes))
+	for _, net := range s.nodes {
+		if n == 0 {
+			return net
+		}
+		n--
+	}
+	return nil
+}
+
+func (s *simulation) launchNode(log bool) *Network {
+	var (
+		num = s.nodectr
+		key = newkey()
+		id  = PubkeyID(&key.PublicKey)
+		ip  = make(net.IP, 4)
+	)
+	s.nodectr++
+	binary.BigEndian.PutUint32(ip, num)
+	ip[0] = 10
+	addr := &net.UDPAddr{IP: ip, Port: 30303}
+
+	transport := &simTransport{joinTime: time.Now(), sender: id, senderAddr: addr, sim: s, priv: key}
+	net, err := newNetwork(transport, key.PublicKey, nil, "<no database>")
+	if err != nil {
+		panic("cannot launch new node: " + err.Error())
+	}
+
+	s.mu.Lock()
+	s.nodes[id] = net
+	s.mu.Unlock()
+
+	return net
+}
+
+func (s *simulation) dropNode(id NodeID) {
+	s.mu.Lock()
+	n := s.nodes[id]
+	delete(s.nodes, id)
+	s.mu.Unlock()
+
+	n.Close()
+}
+
+type simTransport struct {
+	joinTime   time.Time
+	sender     NodeID
+	senderAddr *net.UDPAddr
+	sim        *simulation
+	hashctr    uint64
+	priv       *ecdsa.PrivateKey
+}
+
+func (st *simTransport) localAddr() *net.UDPAddr {
+	return st.senderAddr
+}
+
+func (st *simTransport) Close() {}
+
+func (st *simTransport) send(remote *Node, ptype nodeEvent, data interface{}) (hash []byte) {
+	hash = st.nextHash()
+	var raw []byte
+	if ptype == pongPacket {
+		var err error
+		raw, _, err = encodePacket(st.priv, byte(ptype), data)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       hash,
+		ev:         ptype,
+		data:       data,
+		rawData:    raw,
+	})
+	return hash
+}
+
+func (st *simTransport) sendPing(remote *Node, remoteAddr *net.UDPAddr, topics []Topic) []byte {
+	hash := st.nextHash()
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       hash,
+		ev:         pingPacket,
+		data: &ping{
+			Version:    4,
+			From:       rpcEndpoint{IP: st.senderAddr.IP, UDP: uint16(st.senderAddr.Port), TCP: 30303},
+			To:         rpcEndpoint{IP: remoteAddr.IP, UDP: uint16(remoteAddr.Port), TCP: 30303},
+			Expiration: uint64(time.Now().Unix() + int64(expiration)),
+			Topics:     topics,
+		},
+	})
+	return hash
+}
+
+func (st *simTransport) sendPong(remote *Node, pingHash []byte) {
+	raddr := remote.addr()
+
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       st.nextHash(),
+		ev:         pongPacket,
+		data: &pong{
+			To:         rpcEndpoint{IP: raddr.IP, UDP: uint16(raddr.Port), TCP: 30303},
+			ReplyTok:   pingHash,
+			Expiration: uint64(time.Now().Unix() + int64(expiration)),
+		},
+	})
+}
+
+func (st *simTransport) sendFindnodeHash(remote *Node, target common.Hash) {
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       st.nextHash(),
+		ev:         findnodeHashPacket,
+		data: &findnodeHash{
+			Target:     target,
+			Expiration: uint64(time.Now().Unix() + int64(expiration)),
+		},
+	})
+}
+
+func (st *simTransport) sendTopicRegister(remote *Node, topics []Topic, idx int, pong []byte) {
+	//fmt.Println("send", topics, pong)
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       st.nextHash(),
+		ev:         topicRegisterPacket,
+		data: &topicRegister{
+			Topics: topics,
+			Idx:    uint(idx),
+			Pong:   pong,
+		},
+	})
+}
+
+func (st *simTransport) sendTopicNodes(remote *Node, queryHash common.Hash, nodes []*Node) {
+	rnodes := make([]rpcNode, len(nodes))
+	for i := range nodes {
+		rnodes[i] = nodeToRPC(nodes[i])
+	}
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       st.nextHash(),
+		ev:         topicNodesPacket,
+		data:       &topicNodes{Echo: queryHash, Nodes: rnodes},
+	})
+}
+
+func (st *simTransport) sendNeighbours(remote *Node, nodes []*Node) {
+	// TODO: send multiple packets
+	rnodes := make([]rpcNode, len(nodes))
+	for i := range nodes {
+		rnodes[i] = nodeToRPC(nodes[i])
+	}
+	st.sendPacket(remote.ID, ingressPacket{
+		remoteID:   st.sender,
+		remoteAddr: st.senderAddr,
+		hash:       st.nextHash(),
+		ev:         neighborsPacket,
+		data: &neighbors{
+			Nodes:      rnodes,
+			Expiration: uint64(time.Now().Unix() + int64(expiration)),
+		},
+	})
+}
+
+func (st *simTransport) nextHash() []byte {
+	v := atomic.AddUint64(&st.hashctr, 1)
+	var hash common.Hash
+	binary.BigEndian.PutUint64(hash[:], v)
+	return hash[:]
+}
+
+const packetLoss = 0 // 1/1000
+
+func (st *simTransport) sendPacket(remote NodeID, p ingressPacket) {
+	if rand.Int31n(1000) >= packetLoss {
+		st.sim.mu.RLock()
+		recipient := st.sim.nodes[remote]
+		st.sim.mu.RUnlock()
+
+		time.AfterFunc(200*time.Millisecond, func() {
+			recipient.reqReadPacket(p)
+		})
+	}
+}
diff --git a/p2p/discv5/sim_testmain_test.go b/p2p/discv5/sim_testmain_test.go
new file mode 100644
index 000000000..77e751c41
--- /dev/null
+++ b/p2p/discv5/sim_testmain_test.go
@@ -0,0 +1,43 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// +build go1.4,nacl,faketime_simulation
+
+package discv5
+
+import (
+	"os"
+	"runtime"
+	"testing"
+	"unsafe"
+)
+
+// Enable fake time mode in the runtime, like on the go playground.
+// There is a slight chance that this won't work because some go code
+// might have executed before the variable is set.
+
+//go:linkname faketime runtime.faketime
+var faketime = 1
+
+func TestMain(m *testing.M) {
+	// We need to use unsafe somehow in order to get access to go:linkname.
+	_ = unsafe.Sizeof(0)
+
+	// Run the actual test. runWithPlaygroundTime ensures that the only test
+	// that runs is the one calling it.
+	runtime.GOMAXPROCS(8)
+	os.Exit(m.Run())
+}
diff --git a/p2p/discv5/table.go b/p2p/discv5/table.go
new file mode 100644
index 000000000..31d2ea1b7
--- /dev/null
+++ b/p2p/discv5/table.go
@@ -0,0 +1,305 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+// Package discv5 implements the RLPx v5 Topic Discovery Protocol.
+//
+// The Topic Discovery protocol provides a way to find RLPx nodes that
+// can be connected to. It uses a Kademlia-like protocol to maintain a
+// distributed database of the IDs and endpoints of all listening
+// nodes.
+package discv5
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"net"
+	"sort"
+
+	"github.com/ethereum/go-ethereum/common"
+)
+
+const (
+	alpha      = 3  // Kademlia concurrency factor
+	bucketSize = 16 // Kademlia bucket size
+	hashBits   = len(common.Hash{}) * 8
+	nBuckets   = hashBits + 1 // Number of buckets
+
+	maxBondingPingPongs = 16
+	maxFindnodeFailures = 5
+)
+
+type Table struct {
+	count         int               // number of nodes
+	buckets       [nBuckets]*bucket // index of known nodes by distance
+	nodeAddedHook func(*Node)       // for testing
+	self          *Node             // metadata of the local node
+}
+
+// bucket contains nodes, ordered by their last activity. the entry
+// that was most recently active is the first element in entries.
+type bucket struct {
+	entries      []*Node
+	replacements []*Node
+}
+
+func newTable(ourID NodeID, ourAddr *net.UDPAddr) *Table {
+	self := NewNode(ourID, ourAddr.IP, uint16(ourAddr.Port), uint16(ourAddr.Port))
+	tab := &Table{self: self}
+	for i := range tab.buckets {
+		tab.buckets[i] = new(bucket)
+	}
+	return tab
+}
+
+func (tab *Table) chooseBucketFillTarget() common.Hash {
+	bucketCount := nBuckets
+	for bucketCount > 0 && len(tab.buckets[nBuckets-bucketCount].entries) == 0 {
+		bucketCount--
+	}
+	var bucket int
+	for {
+		// select a target hash that could go into a certain randomly selected bucket
+		// buckets are chosen with an even chance out of the existing ones that contain
+		// less that bucketSize entries, plus a potential new one beyond these
+		bucket = nBuckets - 1 - int(randUint(uint32(bucketCount+1)))
+		if bucket == bucketCount || len(tab.buckets[bucket].entries) < bucketSize {
+			break
+		}
+	}
+
+	// calculate target that has the desired log distance from our own address hash
+	target := tab.self.sha.Bytes()
+	prefix := binary.BigEndian.Uint64(target[0:8])
+	shift := uint(nBuckets - 1 - bucket)
+	if bucket != bucketCount {
+		shift++
+	}
+	var b [8]byte
+	rand.Read(b[:])
+	rnd := binary.BigEndian.Uint64(b[:])
+	rndMask := (^uint64(0)) >> shift
+	addrMask := ^rndMask
+	xorMask := uint64(0)
+	if bucket != bucketCount {
+		xorMask = rndMask + 1
+	}
+	prefix = (prefix&addrMask ^ xorMask) | (rnd & rndMask)
+	binary.BigEndian.PutUint64(target[0:8], prefix)
+	rand.Read(target[8:])
+	return common.BytesToHash(target)
+}
+
+// readRandomNodes fills the given slice with random nodes from the
+// table. It will not write the same node more than once. The nodes in
+// the slice are copies and can be modified by the caller.
+func (tab *Table) readRandomNodes(buf []*Node) (n int) {
+	// TODO: tree-based buckets would help here
+	// Find all non-empty buckets and get a fresh slice of their entries.
+	var buckets [][]*Node
+	for _, b := range tab.buckets {
+		if len(b.entries) > 0 {
+			buckets = append(buckets, b.entries[:])
+		}
+	}
+	if len(buckets) == 0 {
+		return 0
+	}
+	// Shuffle the buckets.
+	for i := uint32(len(buckets)) - 1; i > 0; i-- {
+		j := randUint(i)
+		buckets[i], buckets[j] = buckets[j], buckets[i]
+	}
+	// Move head of each bucket into buf, removing buckets that become empty.
+	var i, j int
+	for ; i < len(buf); i, j = i+1, (j+1)%len(buckets) {
+		b := buckets[j]
+		buf[i] = &(*b[0])
+		buckets[j] = b[1:]
+		if len(b) == 1 {
+			buckets = append(buckets[:j], buckets[j+1:]...)
+		}
+		if len(buckets) == 0 {
+			break
+		}
+	}
+	return i + 1
+}
+
+func randUint(max uint32) uint32 {
+	if max < 2 {
+		return 0
+	}
+	var b [4]byte
+	rand.Read(b[:])
+	return binary.BigEndian.Uint32(b[:]) % max
+}
+
+func randUint64n(max uint64) uint64 {
+	if max < 2 {
+		return 0
+	}
+	var b [8]byte
+	rand.Read(b[:])
+	return binary.BigEndian.Uint64(b[:]) % max
+}
+
+// closest returns the n nodes in the table that are closest to the
+// given id. The caller must hold tab.mutex.
+func (tab *Table) closest(target common.Hash, nresults int) *nodesByDistance {
+	// This is a very wasteful way to find the closest nodes but
+	// obviously correct. I believe that tree-based buckets would make
+	// this easier to implement efficiently.
+	close := &nodesByDistance{target: target}
+	for _, b := range tab.buckets {
+		for _, n := range b.entries {
+			close.push(n, nresults)
+		}
+	}
+	return close
+}
+
+// add attempts to add the given node its corresponding bucket. If the
+// bucket has space available, adding the node succeeds immediately.
+// Otherwise, the node is added to the replacement cache for the bucket.
+func (tab *Table) add(n *Node) (contested *Node) {
+	b := tab.buckets[logdist(tab.self.sha, n.sha)]
+	switch {
+	case b.bump(n):
+		// n exists in b.
+		return nil
+	case len(b.entries) < bucketSize:
+		// b has space available.
+		b.addFront(n)
+		tab.count++
+		if tab.nodeAddedHook != nil {
+			tab.nodeAddedHook(n)
+		}
+		return nil
+	default:
+		// b has no space left, add to replacement cache
+		// and revalidate the last entry.
+		// TODO: drop previous node
+		b.replacements = append(b.replacements, n)
+		if len(b.replacements) > bucketSize {
+			copy(b.replacements, b.replacements[1:])
+			b.replacements = b.replacements[:len(b.replacements)-1]
+		}
+		return b.entries[len(b.entries)-1]
+	}
+}
+
+// stuff adds nodes the table to the end of their corresponding bucket
+// if the bucket is not full.
+func (tab *Table) stuff(nodes []*Node) {
+outer:
+	for _, n := range nodes {
+		if n.ID == tab.self.ID {
+			continue // don't add self
+		}
+		bucket := tab.buckets[logdist(tab.self.sha, n.sha)]
+		for i := range bucket.entries {
+			if bucket.entries[i].ID == n.ID {
+				continue outer // already in bucket
+			}
+		}
+		if len(bucket.entries) < bucketSize {
+			bucket.entries = append(bucket.entries, n)
+			tab.count++
+			if tab.nodeAddedHook != nil {
+				tab.nodeAddedHook(n)
+			}
+		}
+	}
+}
+
+// delete removes an entry from the node table (used to evacuate
+// failed/non-bonded discovery peers).
+func (tab *Table) delete(node *Node) {
+	bucket := tab.buckets[logdist(tab.self.sha, node.sha)]
+	for i := range bucket.entries {
+		if bucket.entries[i].ID == node.ID {
+			bucket.entries = append(bucket.entries[:i], bucket.entries[i+1:]...)
+			tab.count--
+			return
+		}
+	}
+}
+
+func (tab *Table) deleteReplace(node *Node) {
+	b := tab.buckets[logdist(tab.self.sha, node.sha)]
+	i := 0
+	for i < len(b.entries) {
+		if b.entries[i].ID == node.ID {
+			b.entries = append(b.entries[:i], b.entries[i+1:]...)
+			tab.count--
+		} else {
+			i++
+		}
+	}
+	// refill from replacement cache
+	// TODO: maybe use random index
+	if len(b.entries) < bucketSize && len(b.replacements) > 0 {
+		ri := len(b.replacements) - 1
+		b.addFront(b.replacements[ri])
+		tab.count++
+		b.replacements[ri] = nil
+		b.replacements = b.replacements[:ri]
+	}
+}
+
+func (b *bucket) addFront(n *Node) {
+	b.entries = append(b.entries, nil)
+	copy(b.entries[1:], b.entries)
+	b.entries[0] = n
+}
+
+func (b *bucket) bump(n *Node) bool {
+	for i := range b.entries {
+		if b.entries[i].ID == n.ID {
+			// move it to the front
+			copy(b.entries[1:], b.entries[:i])
+			b.entries[0] = n
+			return true
+		}
+	}
+	return false
+}
+
+// nodesByDistance is a list of nodes, ordered by
+// distance to target.
+type nodesByDistance struct {
+	entries []*Node
+	target  common.Hash
+}
+
+// push adds the given node to the list, keeping the total size below maxElems.
+func (h *nodesByDistance) push(n *Node, maxElems int) {
+	ix := sort.Search(len(h.entries), func(i int) bool {
+		return distcmp(h.target, h.entries[i].sha, n.sha) > 0
+	})
+	if len(h.entries) < maxElems {
+		h.entries = append(h.entries, n)
+	}
+	if ix == len(h.entries) {
+		// farther away than all nodes we already have.
+		// if there was room for it, the node is now the last element.
+	} else {
+		// slide existing entries down to make room
+		// this will overwrite the entry we just appended.
+		copy(h.entries[ix+1:], h.entries[ix:])
+		h.entries[ix] = n
+	}
+}
diff --git a/p2p/discv5/table_test.go b/p2p/discv5/table_test.go
new file mode 100644
index 000000000..b7335540a
--- /dev/null
+++ b/p2p/discv5/table_test.go
@@ -0,0 +1,337 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+	"math/rand"
+
+	"net"
+	"reflect"
+	"testing"
+	"testing/quick"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+type nullTransport struct{}
+
+func (nullTransport) sendPing(remote *Node, remoteAddr *net.UDPAddr) []byte { return []byte{1} }
+func (nullTransport) sendPong(remote *Node, pingHash []byte)                {}
+func (nullTransport) sendFindnode(remote *Node, target NodeID)              {}
+func (nullTransport) sendNeighbours(remote *Node, nodes []*Node)            {}
+func (nullTransport) localAddr() *net.UDPAddr                               { return new(net.UDPAddr) }
+func (nullTransport) Close()                                                {}
+
+// func TestTable_pingReplace(t *testing.T) {
+// 	doit := func(newNodeIsResponding, lastInBucketIsResponding bool) {
+// 		transport := newPingRecorder()
+// 		tab, _ := newTable(transport, NodeID{}, &net.UDPAddr{})
+// 		defer tab.Close()
+// 		pingSender := NewNode(MustHexID("a502af0f59b2aab7746995408c79e9ca312d2793cc997e44fc55eda62f0150bbb8c59a6f9269ba3a081518b62699ee807c7c19c20125ddfccca872608af9e370"), net.IP{}, 99, 99)
+//
+// 		// fill up the sender's bucket.
+// 		last := fillBucket(tab, 253)
+//
+// 		// this call to bond should replace the last node
+// 		// in its bucket if the node is not responding.
+// 		transport.responding[last.ID] = lastInBucketIsResponding
+// 		transport.responding[pingSender.ID] = newNodeIsResponding
+// 		tab.bond(true, pingSender.ID, &net.UDPAddr{}, 0)
+//
+// 		// first ping goes to sender (bonding pingback)
+// 		if !transport.pinged[pingSender.ID] {
+// 			t.Error("table did not ping back sender")
+// 		}
+// 		if newNodeIsResponding {
+// 			// second ping goes to oldest node in bucket
+// 			// to see whether it is still alive.
+// 			if !transport.pinged[last.ID] {
+// 				t.Error("table did not ping last node in bucket")
+// 			}
+// 		}
+//
+// 		tab.mutex.Lock()
+// 		defer tab.mutex.Unlock()
+// 		if l := len(tab.buckets[253].entries); l != bucketSize {
+// 			t.Errorf("wrong bucket size after bond: got %d, want %d", l, bucketSize)
+// 		}
+//
+// 		if lastInBucketIsResponding || !newNodeIsResponding {
+// 			if !contains(tab.buckets[253].entries, last.ID) {
+// 				t.Error("last entry was removed")
+// 			}
+// 			if contains(tab.buckets[253].entries, pingSender.ID) {
+// 				t.Error("new entry was added")
+// 			}
+// 		} else {
+// 			if contains(tab.buckets[253].entries, last.ID) {
+// 				t.Error("last entry was not removed")
+// 			}
+// 			if !contains(tab.buckets[253].entries, pingSender.ID) {
+// 				t.Error("new entry was not added")
+// 			}
+// 		}
+// 	}
+//
+// 	doit(true, true)
+// 	doit(false, true)
+// 	doit(true, false)
+// 	doit(false, false)
+// }
+
+func TestBucket_bumpNoDuplicates(t *testing.T) {
+	t.Parallel()
+	cfg := &quick.Config{
+		MaxCount: 1000,
+		Rand:     rand.New(rand.NewSource(time.Now().Unix())),
+		Values: func(args []reflect.Value, rand *rand.Rand) {
+			// generate a random list of nodes. this will be the content of the bucket.
+			n := rand.Intn(bucketSize-1) + 1
+			nodes := make([]*Node, n)
+			for i := range nodes {
+				nodes[i] = nodeAtDistance(common.Hash{}, 200)
+			}
+			args[0] = reflect.ValueOf(nodes)
+			// generate random bump positions.
+			bumps := make([]int, rand.Intn(100))
+			for i := range bumps {
+				bumps[i] = rand.Intn(len(nodes))
+			}
+			args[1] = reflect.ValueOf(bumps)
+		},
+	}
+
+	prop := func(nodes []*Node, bumps []int) (ok bool) {
+		b := &bucket{entries: make([]*Node, len(nodes))}
+		copy(b.entries, nodes)
+		for i, pos := range bumps {
+			b.bump(b.entries[pos])
+			if hasDuplicates(b.entries) {
+				t.Logf("bucket has duplicates after %d/%d bumps:", i+1, len(bumps))
+				for _, n := range b.entries {
+					t.Logf("  %p", n)
+				}
+				return false
+			}
+		}
+		return true
+	}
+	if err := quick.Check(prop, cfg); err != nil {
+		t.Error(err)
+	}
+}
+
+// fillBucket inserts nodes into the given bucket until
+// it is full. The node's IDs dont correspond to their
+// hashes.
+func fillBucket(tab *Table, ld int) (last *Node) {
+	b := tab.buckets[ld]
+	for len(b.entries) < bucketSize {
+		b.entries = append(b.entries, nodeAtDistance(tab.self.sha, ld))
+	}
+	return b.entries[bucketSize-1]
+}
+
+// nodeAtDistance creates a node for which logdist(base, n.sha) == ld.
+// The node's ID does not correspond to n.sha.
+func nodeAtDistance(base common.Hash, ld int) (n *Node) {
+	n = new(Node)
+	n.sha = hashAtDistance(base, ld)
+	copy(n.ID[:], n.sha[:]) // ensure the node still has a unique ID
+	return n
+}
+
+type pingRecorder struct{ responding, pinged map[NodeID]bool }
+
+func newPingRecorder() *pingRecorder {
+	return &pingRecorder{make(map[NodeID]bool), make(map[NodeID]bool)}
+}
+
+func (t *pingRecorder) findnode(toid NodeID, toaddr *net.UDPAddr, target NodeID) ([]*Node, error) {
+	panic("findnode called on pingRecorder")
+}
+func (t *pingRecorder) close() {}
+func (t *pingRecorder) waitping(from NodeID) error {
+	return nil // remote always pings
+}
+func (t *pingRecorder) ping(toid NodeID, toaddr *net.UDPAddr) error {
+	t.pinged[toid] = true
+	if t.responding[toid] {
+		return nil
+	} else {
+		return errTimeout
+	}
+}
+
+func TestTable_closest(t *testing.T) {
+	t.Parallel()
+
+	test := func(test *closeTest) bool {
+		// for any node table, Target and N
+		tab := newTable(test.Self, &net.UDPAddr{})
+		tab.stuff(test.All)
+
+		// check that doClosest(Target, N) returns nodes
+		result := tab.closest(test.Target, test.N).entries
+		if hasDuplicates(result) {
+			t.Errorf("result contains duplicates")
+			return false
+		}
+		if !sortedByDistanceTo(test.Target, result) {
+			t.Errorf("result is not sorted by distance to target")
+			return false
+		}
+
+		// check that the number of results is min(N, tablen)
+		wantN := test.N
+		if tab.count < test.N {
+			wantN = tab.count
+		}
+		if len(result) != wantN {
+			t.Errorf("wrong number of nodes: got %d, want %d", len(result), wantN)
+			return false
+		} else if len(result) == 0 {
+			return true // no need to check distance
+		}
+
+		// check that the result nodes have minimum distance to target.
+		for _, b := range tab.buckets {
+			for _, n := range b.entries {
+				if contains(result, n.ID) {
+					continue // don't run the check below for nodes in result
+				}
+				farthestResult := result[len(result)-1].sha
+				if distcmp(test.Target, n.sha, farthestResult) < 0 {
+					t.Errorf("table contains node that is closer to target but it's not in result")
+					t.Logf("  Target:          %v", test.Target)
+					t.Logf("  Farthest Result: %v", farthestResult)
+					t.Logf("  ID:              %v", n.ID)
+					return false
+				}
+			}
+		}
+		return true
+	}
+	if err := quick.Check(test, quickcfg()); err != nil {
+		t.Error(err)
+	}
+}
+
+func TestTable_ReadRandomNodesGetAll(t *testing.T) {
+	cfg := &quick.Config{
+		MaxCount: 200,
+		Rand:     rand.New(rand.NewSource(time.Now().Unix())),
+		Values: func(args []reflect.Value, rand *rand.Rand) {
+			args[0] = reflect.ValueOf(make([]*Node, rand.Intn(1000)))
+		},
+	}
+	test := func(buf []*Node) bool {
+		tab := newTable(NodeID{}, &net.UDPAddr{})
+		for i := 0; i < len(buf); i++ {
+			ld := cfg.Rand.Intn(len(tab.buckets))
+			tab.stuff([]*Node{nodeAtDistance(tab.self.sha, ld)})
+		}
+		gotN := tab.readRandomNodes(buf)
+		if gotN != tab.count {
+			t.Errorf("wrong number of nodes, got %d, want %d", gotN, tab.count)
+			return false
+		}
+		if hasDuplicates(buf[:gotN]) {
+			t.Errorf("result contains duplicates")
+			return false
+		}
+		return true
+	}
+	if err := quick.Check(test, cfg); err != nil {
+		t.Error(err)
+	}
+}
+
+type closeTest struct {
+	Self   NodeID
+	Target common.Hash
+	All    []*Node
+	N      int
+}
+
+func (*closeTest) Generate(rand *rand.Rand, size int) reflect.Value {
+	t := &closeTest{
+		Self:   gen(NodeID{}, rand).(NodeID),
+		Target: gen(common.Hash{}, rand).(common.Hash),
+		N:      rand.Intn(bucketSize),
+	}
+	for _, id := range gen([]NodeID{}, rand).([]NodeID) {
+		t.All = append(t.All, &Node{ID: id})
+	}
+	return reflect.ValueOf(t)
+}
+
+func hasDuplicates(slice []*Node) bool {
+	seen := make(map[NodeID]bool)
+	for i, e := range slice {
+		if e == nil {
+			panic(fmt.Sprintf("nil *Node at %d", i))
+		}
+		if seen[e.ID] {
+			return true
+		}
+		seen[e.ID] = true
+	}
+	return false
+}
+
+func sortedByDistanceTo(distbase common.Hash, slice []*Node) bool {
+	var last common.Hash
+	for i, e := range slice {
+		if i > 0 && distcmp(distbase, e.sha, last) < 0 {
+			return false
+		}
+		last = e.sha
+	}
+	return true
+}
+
+func contains(ns []*Node, id NodeID) bool {
+	for _, n := range ns {
+		if n.ID == id {
+			return true
+		}
+	}
+	return false
+}
+
+// gen wraps quick.Value so it's easier to use.
+// it generates a random value of the given value's type.
+func gen(typ interface{}, rand *rand.Rand) interface{} {
+	v, ok := quick.Value(reflect.TypeOf(typ), rand)
+	if !ok {
+		panic(fmt.Sprintf("couldn't generate random value of type %T", typ))
+	}
+	return v.Interface()
+}
+
+func newkey() *ecdsa.PrivateKey {
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		panic("couldn't generate key: " + err.Error())
+	}
+	return key
+}
diff --git a/p2p/discv5/testimg/1 b/p2p/discv5/testimg/1
new file mode 100644
index 000000000..f2acfdc06
--- /dev/null
+++ b/p2p/discv5/testimg/1
@@ -0,0 +1,173 @@
+package main
+
+import (
+	"bufio"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+	"sort"
+	"strconv"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+var xs, ys, maxTime int
+
+func set(pic *image.NRGBA, x, y, c, v int) {
+	if v > 255 {
+		v = 255
+	}
+	if x >= 0 && x < xs && y >= 0 && y < ys {
+		pic.Pix[y*pic.Stride+x*4+c] = uint8(v)
+	}
+}
+
+func main() {
+	topicHash := crypto.Keccak256Hash([]byte("foo"))
+	fmt.Println(topicHash)
+	topicPrefix := binary.BigEndian.Uint64(topicHash[:8])
+	var nodes uint64Slice
+
+	inputFile := "test.out"
+	if len(os.Args) > 1 {
+		inputFile = os.Args[1]
+	}
+
+	f, _ := os.Open(inputFile)
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*N" {
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			nodes = append(nodes, prefix^topicPrefix)
+		}
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if int(time) > maxTime {
+				maxTime = int(time)
+			}
+		}
+	}
+	f.Close()
+	sort.Sort(nodes)
+	nodeIdx := make(map[uint64]int)
+	for i, v := range nodes {
+		nodeIdx[v^topicPrefix] = i
+	}
+
+	xs = maxTime / 10000
+	ys = len(nodes)
+
+	pic := image.NewNRGBA(image.Rect(0, 0, xs, ys))
+	for y := 0; y < ys; y++ {
+		for x := 0; x < xs; x++ {
+			set(pic, x, y, 3, 255)
+		}
+	}
+
+	pic2 := image.NewNRGBA(image.Rect(0, 0, xs, ys))
+	for y := 0; y < ys; y++ {
+		for x := 0; x < xs; x++ {
+			set(pic2, x, y, 3, 255)
+		}
+	}
+
+	f, _ = os.Open(inputFile)
+	scanner = bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+
+	nodeRad := make(map[uint64]int)
+
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if int(rad) != nodeRad[prefix] {
+				nodeRad[prefix] = int(rad)
+				radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+				x := int(time * int64(xs) / int64(maxTime))
+				y := sort.Search(ys, func(i int) bool {
+					return nodes[i] > radUint
+				})
+				set(pic, x, y, 1, 255)
+			}
+		}
+		if w == "*MR" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			scanner.Scan()
+			rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := sort.Search(ys, func(i int) bool {
+				return nodes[i] > radUint
+			})
+			set(pic, x, y, 0, 255)
+		}
+		if w == "*W" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			wp, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := nodeIdx[prefix]
+			set(pic2, x, y, 0, int(wp/100000))
+			set(pic2, x, y, 1, int(wp/10000))
+			set(pic2, x, y, 2, int(wp/1000))
+		}
+		if w == "*+" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := nodeIdx[prefix]
+			set(pic, x, y, 2, 255)
+			scanner.Scan()
+		}
+	}
+	f.Close()
+
+	f, _ = os.Create("test.png")
+	w := bufio.NewWriter(f)
+	png.Encode(w, pic)
+	w.Flush()
+	f.Close()
+
+	f, _ = os.Create("test2.png")
+	w = bufio.NewWriter(f)
+	png.Encode(w, pic2)
+	w.Flush()
+	f.Close()
+}
+
+type uint64Slice []uint64
+
+// Len is the number of elements in the collection.
+func (s uint64Slice) Len() int {
+	return len(s)
+}
+
+// Less reports whether the element with
+// index i should sort before the element with index j.
+func (s uint64Slice) Less(i, j int) bool {
+	return s[i] < s[j]
+}
+
+// Swap swaps the elements with indexes i and j.
+func (s uint64Slice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
diff --git a/p2p/discv5/testimg/2 b/p2p/discv5/testimg/2
new file mode 100644
index 000000000..2638eff4f
--- /dev/null
+++ b/p2p/discv5/testimg/2
@@ -0,0 +1,178 @@
+package main
+
+import (
+	"bufio"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+	"sort"
+	"strconv"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+var xs, ys, maxTime int
+
+func set(pic *image.NRGBA, x, y, c, v int) {
+	if v > 255 {
+		v = 255
+	}
+	if x >= 0 && x < xs && y >= 0 && y < ys {
+		pic.Pix[y*pic.Stride+x*4+c] = uint8(v)
+	}
+}
+
+func main() {
+	topics := make(map[string]uint64)
+	var nodes uint64Slice
+
+	inputFile := "test.out"
+	if len(os.Args) > 1 {
+		inputFile = os.Args[1]
+	}
+
+	f, _ := os.Open(inputFile)
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*N" {
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			nodes = append(nodes, prefix^topicPrefix)
+		}
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if int(time) > maxTime {
+				maxTime = int(time)
+			}
+			scanner.Scan()
+			topic := scanner.Text()
+			if _, ok := topics[topic]; !ok {
+				fmt.Println(topic)
+				topicHash := crypto.Keccak256Hash([]byte(topic))
+				topics[topic] := binary.BigEndian.Uint64(topicHash[:8])
+			}
+		}
+	}
+	f.Close()
+	sort.Sort(nodes)
+	nodeIdx := make(map[uint64]int)
+	for i, v := range nodes {
+		nodeIdx[v^topicPrefix] = i
+	}
+
+	xs = maxTime / 10000
+	ys = len(nodes)
+
+	pic := image.NewNRGBA(image.Rect(0, 0, xs, ys))
+	for y := 0; y < ys; y++ {
+		for x := 0; x < xs; x++ {
+			set(pic, x, y, 3, 255)
+		}
+	}
+
+	pic2 := image.NewNRGBA(image.Rect(0, 0, xs, ys))
+	for y := 0; y < ys; y++ {
+		for x := 0; x < xs; x++ {
+			set(pic2, x, y, 3, 255)
+		}
+	}
+
+	f, _ = os.Open(inputFile)
+	scanner = bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+
+	nodeRad := make(map[uint64]int)
+
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if int(rad) != nodeRad[prefix] {
+				nodeRad[prefix] = int(rad)
+				radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+				x := int(time * int64(xs) / int64(maxTime))
+				y := sort.Search(ys, func(i int) bool {
+					return nodes[i] > radUint
+				})
+				set(pic, x, y, 1, 255)
+			}
+		}
+		if w == "*MR" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			scanner.Scan()
+			rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := sort.Search(ys, func(i int) bool {
+				return nodes[i] > radUint
+			})
+			set(pic, x, y, 0, 255)
+		}
+		if w == "*W" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			wp, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := nodeIdx[prefix]
+			set(pic2, x, y, 0, int(wp/100000))
+			set(pic2, x, y, 1, int(wp/10000))
+			set(pic2, x, y, 2, int(wp/1000))
+		}
+		if w == "*+" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := nodeIdx[prefix]
+			set(pic, x, y, 2, 255)
+			scanner.Scan()
+		}
+	}
+	f.Close()
+
+	f, _ = os.Create("test.png")
+	w := bufio.NewWriter(f)
+	png.Encode(w, pic)
+	w.Flush()
+	f.Close()
+
+	f, _ = os.Create("test2.png")
+	w = bufio.NewWriter(f)
+	png.Encode(w, pic2)
+	w.Flush()
+	f.Close()
+}
+
+type uint64Slice []uint64
+
+// Len is the number of elements in the collection.
+func (s uint64Slice) Len() int {
+	return len(s)
+}
+
+// Less reports whether the element with
+// index i should sort before the element with index j.
+func (s uint64Slice) Less(i, j int) bool {
+	return s[i] < s[j]
+}
+
+// Swap swaps the elements with indexes i and j.
+func (s uint64Slice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
diff --git a/p2p/discv5/testimg/testimg.1 b/p2p/discv5/testimg/testimg.1
new file mode 100644
index 000000000..32268aa97
--- /dev/null
+++ b/p2p/discv5/testimg/testimg.1
@@ -0,0 +1,191 @@
+package main
+
+import (
+	"bufio"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/png"
+	"os"
+	"sort"
+	"strconv"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+var xs, ys, maxTime int
+
+func set(pic *image.NRGBA, x, y, c, v int) {
+	if v > 255 {
+		v = 255
+	}
+	if x >= 0 && x < xs && y >= 0 && y < ys {
+		pic.Pix[y*pic.Stride+x*4+c] = uint8(v)
+	}
+}
+
+func main() {
+	var nodes uint64Slice
+
+	inputFile := "test.out"
+	if len(os.Args) > 1 {
+		inputFile = os.Args[1]
+	}
+
+	topic := "foo"
+	if len(os.Args) > 2 {
+		topic = os.Args[2]
+	}
+
+	topicHash := crypto.Keccak256Hash([]byte(topic))
+	fmt.Println(topicHash)
+	topicPrefix := binary.BigEndian.Uint64(topicHash[:8])
+
+	f, _ := os.Open(inputFile)
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*N" {
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			nodes = append(nodes, prefix^topicPrefix)
+		}
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if int(time) > maxTime {
+				maxTime = int(time)
+			}
+		}
+	}
+	f.Close()
+	sort.Sort(nodes)
+	nodeIdx := make(map[uint64]int)
+	for i, v := range nodes {
+		nodeIdx[v^topicPrefix] = i
+	}
+
+	xs = maxTime / 10000
+	ys = len(nodes)
+
+	pic := image.NewNRGBA(image.Rect(0, 0, xs, ys))
+	for y := 0; y < ys; y++ {
+		for x := 0; x < xs; x++ {
+			set(pic, x, y, 3, 255)
+		}
+	}
+
+	pic2 := image.NewNRGBA(image.Rect(0, 0, xs, ys))
+	for y := 0; y < ys; y++ {
+		for x := 0; x < xs; x++ {
+			set(pic2, x, y, 3, 255)
+		}
+	}
+
+	f, _ = os.Open(inputFile)
+	scanner = bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+
+	nodeRad := make(map[uint64]int)
+
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			if scanner.Text() == topic {
+				scanner.Scan()
+				prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+				scanner.Scan()
+				rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+				if int(rad) != nodeRad[prefix] {
+					nodeRad[prefix] = int(rad)
+					radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+					x := int(time * int64(xs) / int64(maxTime))
+					y := sort.Search(ys, func(i int) bool {
+						return nodes[i] > radUint
+					})
+					set(pic, x, y, 1, 255)
+				}
+			}
+		}
+		if w == "*MR" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			if scanner.Text() == topic {
+				scanner.Scan()
+				scanner.Scan()
+				rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+				radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+				x := int(time * int64(xs) / int64(maxTime))
+				y := sort.Search(ys, func(i int) bool {
+					return nodes[i] > radUint
+				})
+				set(pic, x, y, 0, 255)
+			}
+		}
+		if w == "*W" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			if scanner.Text() == topic {
+				scanner.Scan()
+				prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+				scanner.Scan()
+				wp, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+				x := int(time * int64(xs) / int64(maxTime))
+				y := nodeIdx[prefix]
+				set(pic2, x, y, 0, int(wp/100000))
+				set(pic2, x, y, 1, int(wp/10000))
+				set(pic2, x, y, 2, int(wp/1000))
+			}
+		}
+		if w == "*+" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			scanner.Scan()
+			if scanner.Text() == topic {
+				scanner.Scan()
+				prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+				x := int(time * int64(xs) / int64(maxTime))
+				y := nodeIdx[prefix]
+				set(pic, x, y, 2, 255)
+				scanner.Scan()
+			}
+		}
+	}
+	f.Close()
+
+	f, _ = os.Create("test.png")
+	w := bufio.NewWriter(f)
+	png.Encode(w, pic)
+	w.Flush()
+	f.Close()
+
+	f, _ = os.Create("test2.png")
+	w = bufio.NewWriter(f)
+	png.Encode(w, pic2)
+	w.Flush()
+	f.Close()
+}
+
+type uint64Slice []uint64
+
+// Len is the number of elements in the collection.
+func (s uint64Slice) Len() int {
+	return len(s)
+}
+
+// Less reports whether the element with
+// index i should sort before the element with index j.
+func (s uint64Slice) Less(i, j int) bool {
+	return s[i] < s[j]
+}
+
+// Swap swaps the elements with indexes i and j.
+func (s uint64Slice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
diff --git a/p2p/discv5/testimg/testimg.go b/p2p/discv5/testimg/testimg.go
new file mode 100644
index 000000000..dab918a77
--- /dev/null
+++ b/p2p/discv5/testimg/testimg.go
@@ -0,0 +1,335 @@
+package main
+
+import (
+	"bufio"
+	"encoding/binary"
+	"fmt"
+	"image"
+	"image/png"
+	"math"
+	"os"
+	"sort"
+	"strconv"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+var xs, ys, maxTime int
+var minAbsTime, maxAbsTime int64
+
+func set(pic *image.NRGBA, x, y, c, v int) {
+	if v > 255 {
+		v = 255
+	}
+	if x >= 0 && x < xs && y >= 0 && y < ys {
+		pic.Pix[y*pic.Stride+x*4+c] = uint8(v)
+	}
+}
+
+type nodeStats []struct{ wpSum, wpCnt, wpXcnt, regCnt, regXcnt uint64 }
+
+type nodeInfo struct {
+	maxMR  int
+	topics map[string]struct{}
+}
+
+const (
+	regStatDiv  = 60
+	regStatYdiv = 30
+)
+
+type topicInfo struct {
+	prefix    uint64
+	nodes     uint64Slice
+	nodeStats nodeStats
+	nodeIdx   map[uint64]int
+	pic, pic2 *image.NRGBA
+	nodeRad   map[uint64]int
+	regStats  []int
+}
+
+func main() {
+	var nodes uint64Slice
+	topics := make(map[string]*topicInfo)
+
+	inputFile := "test.out"
+	if len(os.Args) > 1 {
+		inputFile = os.Args[1]
+	}
+
+	f, _ := os.Open(inputFile)
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+	minAbsTime = math.MaxInt64
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*N" {
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			nodes = append(nodes, prefix)
+		}
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if time > maxAbsTime {
+				maxAbsTime = time
+			}
+			if time < minAbsTime {
+				minAbsTime = time
+			}
+			scanner.Scan()
+			topic := scanner.Text()
+			if _, ok := topics[topic]; !ok {
+				fmt.Println(topic)
+				topicHash := crypto.Keccak256Hash([]byte(topic))
+				topics[topic] = &topicInfo{prefix: binary.BigEndian.Uint64(topicHash[:8])}
+			}
+		}
+	}
+	f.Close()
+
+	maxTime = int(maxAbsTime - minAbsTime)
+	xs = maxTime / 10000
+	ys = len(nodes)
+	nodeIdx := make(map[uint64]int)
+	for i, v := range nodes {
+		nodeIdx[v] = i
+	}
+	nodeInfo := make([]nodeInfo, len(nodes))
+
+	for _, t := range topics {
+		t.nodes = make(uint64Slice, len(nodes))
+		t.nodeStats = make(nodeStats, len(nodes))
+		for i, v := range nodes {
+			t.nodes[i] = v ^ t.prefix
+		}
+		sort.Sort(t.nodes)
+		t.nodeIdx = make(map[uint64]int)
+		for i, v := range t.nodes {
+			t.nodeIdx[v^t.prefix] = i
+		}
+
+		t.pic = image.NewNRGBA(image.Rect(0, 0, xs, ys))
+		for y := 0; y < ys; y++ {
+			for x := 0; x < xs; x++ {
+				set(t.pic, x, y, 3, 255)
+			}
+		}
+
+		t.pic2 = image.NewNRGBA(image.Rect(0, 0, xs, ys))
+		for y := 0; y < ys; y++ {
+			for x := 0; x < xs; x++ {
+				set(t.pic2, x, y, 3, 255)
+			}
+		}
+		t.nodeRad = make(map[uint64]int)
+		t.regStats = make([]int, xs/regStatDiv+1)
+	}
+
+	f, _ = os.Open(inputFile)
+	scanner = bufio.NewScanner(f)
+	scanner.Split(bufio.ScanWords)
+	statBegin := int64(40000000)
+	statEnd := int64(maxTime - 10000000)
+
+	for scanner.Scan() {
+		w := scanner.Text()
+		if w == "*R" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			time -= minAbsTime
+			scanner.Scan()
+			t := topics[scanner.Text()]
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			if int(rad) != t.nodeRad[prefix] {
+				t.nodeRad[prefix] = int(rad)
+				radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+				x := int(time * int64(xs) / int64(maxTime))
+				y := sort.Search(ys, func(i int) bool {
+					return t.nodes[i] > radUint
+				})
+				set(t.pic, x, y, 1, 255)
+			}
+		}
+		if w == "*MR" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			time -= minAbsTime
+			scanner.Scan()
+			topic := scanner.Text()
+			t := topics[topic]
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			rad, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			radUint := uint64(rad) * ((^uint64(0)) / 1000000)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := sort.Search(ys, func(i int) bool {
+				return t.nodes[i] > radUint
+			})
+			set(t.pic, x, y, 0, 255)
+			ni := nodeInfo[nodeIdx[prefix]]
+			if int(rad) > ni.maxMR {
+				ni.maxMR = int(rad)
+				if ni.topics == nil {
+					ni.topics = make(map[string]struct{})
+				}
+				ni.topics[topic] = struct{}{}
+			}
+			nodeInfo[nodeIdx[prefix]] = ni
+		}
+		if w == "*W" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			time -= minAbsTime
+			scanner.Scan()
+			t := topics[scanner.Text()]
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			scanner.Scan()
+			wp, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			x := int(time * int64(xs) / int64(maxTime))
+			y := t.nodeIdx[prefix]
+			if time >= statBegin && time < statEnd {
+				t.nodeStats[y].wpSum += uint64(wp)
+				if wp >= 600000 {
+					t.nodeStats[y].wpXcnt++
+				}
+				t.nodeStats[y].wpCnt++
+			}
+			/*set(t.pic2, x, y, 0, int(wp/100000))
+			set(t.pic2, x, y, 1, int(wp/10000))
+			set(t.pic2, x, y, 2, int(wp/1000))*/
+			if wp >= 1800000 {
+				set(t.pic2, x, y, 0, 255)
+			}
+			if wp >= 600000 {
+				set(t.pic2, x, y, 1, 255)
+			}
+			if wp >= 60000 {
+				set(t.pic2, x, y, 2, 255)
+			}
+		}
+		if w == "*+" {
+			scanner.Scan()
+			time, _ := strconv.ParseInt(scanner.Text(), 10, 64)
+			time -= minAbsTime
+			scanner.Scan()
+			t := topics[scanner.Text()]
+			scanner.Scan()
+			prefix, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			x := int(time * int64(xs) / int64(maxTime))
+			if x < xs {
+				t.regStats[x/regStatDiv]++
+			}
+			y := t.nodeIdx[prefix]
+			set(t.pic, x, y, 2, 255)
+			scanner.Scan()
+			prefix2, _ := strconv.ParseUint(scanner.Text(), 16, 64)
+			y2 := t.nodeIdx[prefix2]
+			if time >= statBegin && time < statEnd {
+				t.nodeStats[y].regCnt++
+				t.nodeStats[y2].regXcnt++
+			}
+		}
+	}
+	f.Close()
+
+	for tt, t := range topics {
+		f, _ = os.Create("test_" + tt + ".png")
+		w := bufio.NewWriter(f)
+		png.Encode(w, t.pic)
+		w.Flush()
+		f.Close()
+
+		for x := 0; x < xs; x++ {
+			yy := t.regStats[x/regStatDiv] / regStatYdiv
+			if yy > ys {
+				yy = ys
+			}
+			for y := 0; y < yy; y++ {
+				set(t.pic2, x, ys-1-y, 1, 255)
+			}
+		}
+
+		f, _ = os.Create("test2_" + tt + ".png")
+		w = bufio.NewWriter(f)
+		png.Encode(w, t.pic2)
+		w.Flush()
+		f.Close()
+
+		if statEnd > statBegin {
+			xxs := len(t.nodeStats)
+			yys := 1000
+			yyh := yys / 2
+			pic3 := image.NewNRGBA(image.Rect(0, 0, xxs, yys))
+			for y := 0; y < yys; y++ {
+				for x := 0; x < xxs; x++ {
+					set(pic3, x, y, 3, 255)
+				}
+			}
+			for x := 0; x < xxs; x++ {
+				wpy := 0
+				if t.nodeStats[x].wpCnt > 0 {
+					//					wpy = int(t.nodeStats[x].wpSum / t.nodeStats[x].wpCnt / 10000)
+					wpy = int(uint64(yyh) * t.nodeStats[x].wpXcnt / t.nodeStats[x].wpCnt)
+				}
+				if wpy > yyh {
+					wpy = yyh
+				}
+				for y := 0; y < wpy; y++ {
+					set(pic3, x, yys-1-y, 1, 255)
+				}
+				regy := int(t.nodeStats[x].regCnt * 2400000 / uint64(statEnd-statBegin))
+				if regy > yyh {
+					regy = yyh
+				}
+				for y := 0; y < regy; y++ {
+					set(pic3, x, yyh-1-y, 2, 255)
+				}
+				regy2 := int(t.nodeStats[x].regXcnt * 2400000 / uint64(statEnd-statBegin))
+				if regy2 > yyh {
+					regy2 = yyh
+				}
+				for y := 0; y < regy2; y++ {
+					set(pic3, x, yyh-1-y, 0, 255)
+				}
+			}
+
+			f, _ = os.Create("test3_" + tt + ".png")
+			w = bufio.NewWriter(f)
+			png.Encode(w, pic3)
+			w.Flush()
+			f.Close()
+		}
+	}
+
+	for i, ni := range nodeInfo {
+		fmt.Printf("%d %016x  maxMR = %d  ", i, nodes[i], ni.maxMR)
+		for t, _ := range ni.topics {
+			fmt.Printf(" %s", t)
+		}
+		fmt.Println()
+	}
+}
+
+type uint64Slice []uint64
+
+// Len is the number of elements in the collection.
+func (s uint64Slice) Len() int {
+	return len(s)
+}
+
+// Less reports whether the element with
+// index i should sort before the element with index j.
+func (s uint64Slice) Less(i, j int) bool {
+	return s[i] < s[j]
+}
+
+// Swap swaps the elements with indexes i and j.
+func (s uint64Slice) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
diff --git a/p2p/discv5/ticket.go b/p2p/discv5/ticket.go
new file mode 100644
index 000000000..e256d7679
--- /dev/null
+++ b/p2p/discv5/ticket.go
@@ -0,0 +1,953 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"math"
+	"math/rand"
+	"sort"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/mclock"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+const (
+	ticketTimeBucketLen = time.Minute
+	timeWindow          = 10 // * ticketTimeBucketLen
+	wantTicketsInWindow = 10
+	collectFrequency    = time.Second * 30
+	registerFrequency   = time.Second * 60
+	maxCollectDebt      = 10
+	maxRegisterDebt     = 5
+	keepTicketConst     = time.Minute * 10
+	keepTicketExp       = time.Minute * 5
+	targetWaitTime      = time.Minute * 10
+	topicQueryTimeout   = time.Second * 5
+	topicQueryResend    = time.Minute
+	// topic radius detection
+	maxRadius           = 0xffffffffffffffff
+	radiusTC            = time.Minute * 20
+	radiusBucketsPerBit = 8
+	minSlope            = 1
+	minPeakSize         = 40
+	maxNoAdjust         = 20
+	lookupWidth         = 8
+	minRightSum         = 20
+	searchForceQuery    = 4
+)
+
+// timeBucket represents absolute monotonic time in minutes.
+// It is used as the index into the per-topic ticket buckets.
+type timeBucket int
+
+type ticket struct {
+	topics  []Topic
+	regTime []mclock.AbsTime // Per-topic local absolute time when the ticket can be used.
+
+	// The serial number that was issued by the server.
+	serial uint32
+	// Used by registrar, tracks absolute time when the ticket was created.
+	issueTime mclock.AbsTime
+
+	// Fields used only by registrants
+	node   *Node  // the registrar node that signed this ticket
+	refCnt int    // tracks number of topics that will be registered using this ticket
+	pong   []byte // encoded pong packet signed by the registrar
+}
+
+// ticketRef refers to a single topic in a ticket.
+type ticketRef struct {
+	t   *ticket
+	idx int // index of the topic in t.topics and t.regTime
+}
+
+func (ref ticketRef) topic() Topic {
+	return ref.t.topics[ref.idx]
+}
+
+func (ref ticketRef) topicRegTime() mclock.AbsTime {
+	return ref.t.regTime[ref.idx]
+}
+
+func pongToTicket(localTime mclock.AbsTime, topics []Topic, node *Node, p *ingressPacket) (*ticket, error) {
+	wps := p.data.(*pong).WaitPeriods
+	if len(topics) != len(wps) {
+		return nil, fmt.Errorf("bad wait period list: got %d values, want %d", len(topics), len(wps))
+	}
+	if rlpHash(topics) != p.data.(*pong).TopicHash {
+		return nil, fmt.Errorf("bad topic hash")
+	}
+	t := &ticket{
+		issueTime: localTime,
+		node:      node,
+		topics:    topics,
+		pong:      p.rawData,
+		regTime:   make([]mclock.AbsTime, len(wps)),
+	}
+	// Convert wait periods to local absolute time.
+	for i, wp := range wps {
+		t.regTime[i] = localTime + mclock.AbsTime(time.Second*time.Duration(wp))
+	}
+	return t, nil
+}
+
+func ticketToPong(t *ticket, pong *pong) {
+	pong.Expiration = uint64(t.issueTime / mclock.AbsTime(time.Second))
+	pong.TopicHash = rlpHash(t.topics)
+	pong.TicketSerial = t.serial
+	pong.WaitPeriods = make([]uint32, len(t.regTime))
+	for i, regTime := range t.regTime {
+		pong.WaitPeriods[i] = uint32(time.Duration(regTime-t.issueTime) / time.Second)
+	}
+}
+
+type ticketStore struct {
+	// radius detector and target address generator
+	// exists for both searched and registered topics
+	radius map[Topic]*topicRadius
+
+	// Contains buckets (for each absolute minute) of tickets
+	// that can be used in that minute.
+	// This is only set if the topic is being registered.
+	tickets     map[Topic]topicTickets
+	regtopics   []Topic
+	nodes       map[*Node]*ticket
+	nodeLastReq map[*Node]reqInfo
+
+	lastBucketFetched timeBucket
+	nextTicketCached  *ticketRef
+	nextTicketReg     mclock.AbsTime
+
+	searchTopicMap        map[Topic]searchTopic
+	searchTopicList       []Topic
+	searchTopicPtr        int
+	nextTopicQueryCleanup mclock.AbsTime
+	queriesSent           map[*Node]map[common.Hash]sentQuery
+	radiusLookupCnt       int
+}
+
+type searchTopic struct {
+	foundChn chan<- string
+	listIdx  int
+}
+
+type sentQuery struct {
+	sent   mclock.AbsTime
+	lookup lookupInfo
+}
+
+type topicTickets struct {
+	buckets             map[timeBucket][]ticketRef
+	nextLookup, nextReg mclock.AbsTime
+}
+
+func newTicketStore() *ticketStore {
+	return &ticketStore{
+		radius:         make(map[Topic]*topicRadius),
+		tickets:        make(map[Topic]topicTickets),
+		nodes:          make(map[*Node]*ticket),
+		nodeLastReq:    make(map[*Node]reqInfo),
+		searchTopicMap: make(map[Topic]searchTopic),
+		queriesSent:    make(map[*Node]map[common.Hash]sentQuery),
+	}
+}
+
+// addTopic starts tracking a topic. If register is true,
+// the local node will register the topic and tickets will be collected.
+func (s *ticketStore) addTopic(t Topic, register bool) {
+	debugLog(fmt.Sprintf(" addTopic(%v, %v)", t, register))
+	if s.radius[t] == nil {
+		s.radius[t] = newTopicRadius(t)
+	}
+	if register && s.tickets[t].buckets == nil {
+		s.tickets[t] = topicTickets{buckets: make(map[timeBucket][]ticketRef)}
+	}
+}
+
+func (s *ticketStore) addSearchTopic(t Topic, foundChn chan<- string) {
+	s.addTopic(t, false)
+	if s.searchTopicMap[t].foundChn == nil {
+		s.searchTopicList = append(s.searchTopicList, t)
+		s.searchTopicMap[t] = searchTopic{foundChn: foundChn, listIdx: len(s.searchTopicList) - 1}
+	}
+}
+
+func (s *ticketStore) removeSearchTopic(t Topic) {
+	if st := s.searchTopicMap[t]; st.foundChn != nil {
+		lastIdx := len(s.searchTopicList) - 1
+		lastTopic := s.searchTopicList[lastIdx]
+		s.searchTopicList[st.listIdx] = lastTopic
+		sl := s.searchTopicMap[lastTopic]
+		sl.listIdx = st.listIdx
+		s.searchTopicMap[lastTopic] = sl
+		s.searchTopicList = s.searchTopicList[:lastIdx]
+		delete(s.searchTopicMap, t)
+	}
+}
+
+// removeRegisterTopic deletes all tickets for the given topic.
+func (s *ticketStore) removeRegisterTopic(topic Topic) {
+	debugLog(fmt.Sprintf(" removeRegisterTopic(%v)", topic))
+	for _, list := range s.tickets[topic].buckets {
+		for _, ref := range list {
+			ref.t.refCnt--
+			if ref.t.refCnt == 0 {
+				delete(s.nodes, ref.t.node)
+				delete(s.nodeLastReq, ref.t.node)
+			}
+		}
+	}
+	delete(s.tickets, topic)
+}
+
+func (s *ticketStore) regTopicSet() []Topic {
+	topics := make([]Topic, 0, len(s.tickets))
+	for topic := range s.tickets {
+		topics = append(topics, topic)
+	}
+	return topics
+}
+
+// nextRegisterLookup returns the target of the next lookup for ticket collection.
+func (s *ticketStore) nextRegisterLookup() (lookup lookupInfo, delay time.Duration) {
+	debugLog("nextRegisterLookup()")
+	firstTopic, ok := s.iterRegTopics()
+	for topic := firstTopic; ok; {
+		debugLog(fmt.Sprintf(" checking topic %v, len(s.tickets[topic]) = %d", topic, len(s.tickets[topic].buckets)))
+		if s.tickets[topic].buckets != nil && s.needMoreTickets(topic) {
+			next := s.radius[topic].nextTarget(false)
+			debugLog(fmt.Sprintf(" %x 1s", next.target[:8]))
+			return next, 100 * time.Millisecond
+		}
+		topic, ok = s.iterRegTopics()
+		if topic == firstTopic {
+			break // We have checked all topics.
+		}
+	}
+	debugLog(" null, 40s")
+	return lookupInfo{}, 40 * time.Second
+}
+
+func (s *ticketStore) nextSearchLookup() lookupInfo {
+	if len(s.searchTopicList) == 0 {
+		return lookupInfo{}
+	}
+	if s.searchTopicPtr >= len(s.searchTopicList) {
+		s.searchTopicPtr = 0
+	}
+	topic := s.searchTopicList[s.searchTopicPtr]
+	s.searchTopicPtr++
+	target := s.radius[topic].nextTarget(s.radiusLookupCnt >= searchForceQuery)
+	if target.radiusLookup {
+		s.radiusLookupCnt++
+	} else {
+		s.radiusLookupCnt = 0
+	}
+	return target
+}
+
+// iterRegTopics returns topics to register in arbitrary order.
+// The second return value is false if there are no topics.
+func (s *ticketStore) iterRegTopics() (Topic, bool) {
+	debugLog("iterRegTopics()")
+	if len(s.regtopics) == 0 {
+		if len(s.tickets) == 0 {
+			debugLog(" false")
+			return "", false
+		}
+		// Refill register list.
+		for t := range s.tickets {
+			s.regtopics = append(s.regtopics, t)
+		}
+	}
+	topic := s.regtopics[len(s.regtopics)-1]
+	s.regtopics = s.regtopics[:len(s.regtopics)-1]
+	debugLog(" " + string(topic) + " true")
+	return topic, true
+}
+
+func (s *ticketStore) needMoreTickets(t Topic) bool {
+	return s.tickets[t].nextLookup < mclock.Now()
+}
+
+// ticketsInWindow returns the tickets of a given topic in the registration window.
+func (s *ticketStore) ticketsInWindow(t Topic) []ticketRef {
+	ltBucket := s.lastBucketFetched
+	var res []ticketRef
+	tickets := s.tickets[t].buckets
+	for g := ltBucket; g < ltBucket+timeWindow; g++ {
+		res = append(res, tickets[g]...)
+	}
+	debugLog(fmt.Sprintf("ticketsInWindow(%v) = %v", t, len(res)))
+	return res
+}
+
+func (s *ticketStore) removeExcessTickets(t Topic) {
+	tickets := s.ticketsInWindow(t)
+	if len(tickets) <= wantTicketsInWindow {
+		return
+	}
+	sort.Sort(ticketRefByWaitTime(tickets))
+	for _, r := range tickets[wantTicketsInWindow:] {
+		s.removeTicketRef(r)
+	}
+}
+
+type ticketRefByWaitTime []ticketRef
+
+// Len is the number of elements in the collection.
+func (s ticketRefByWaitTime) Len() int {
+	return len(s)
+}
+
+func (r ticketRef) waitTime() mclock.AbsTime {
+	return r.t.regTime[r.idx] - r.t.issueTime
+}
+
+// Less reports whether the element with
+// index i should sort before the element with index j.
+func (s ticketRefByWaitTime) Less(i, j int) bool {
+	return s[i].waitTime() < s[j].waitTime()
+}
+
+// Swap swaps the elements with indexes i and j.
+func (s ticketRefByWaitTime) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s *ticketStore) addTicketRef(r ticketRef) {
+	topic := r.t.topics[r.idx]
+	t := s.tickets[topic]
+	if t.buckets == nil {
+		return
+	}
+	bucket := timeBucket(r.t.regTime[r.idx] / mclock.AbsTime(ticketTimeBucketLen))
+	t.buckets[bucket] = append(t.buckets[bucket], r)
+	r.t.refCnt++
+
+	min := mclock.Now() - mclock.AbsTime(collectFrequency)*maxCollectDebt
+	if t.nextLookup < min {
+		t.nextLookup = min
+	}
+	t.nextLookup += mclock.AbsTime(collectFrequency)
+	s.tickets[topic] = t
+
+	//s.removeExcessTickets(topic)
+}
+
+func (s *ticketStore) nextFilteredTicket() (t *ticketRef, wait time.Duration) {
+	now := mclock.Now()
+	for {
+		t, wait = s.nextRegisterableTicket()
+		if t == nil {
+			return
+		}
+		regTime := now + mclock.AbsTime(wait)
+		topic := t.t.topics[t.idx]
+		if regTime >= s.tickets[topic].nextReg {
+			return
+		}
+		s.removeTicketRef(*t)
+	}
+}
+
+func (s *ticketStore) ticketRegistered(t ticketRef) {
+	now := mclock.Now()
+
+	topic := t.t.topics[t.idx]
+	tt := s.tickets[topic]
+	min := now - mclock.AbsTime(registerFrequency)*maxRegisterDebt
+	if min > tt.nextReg {
+		tt.nextReg = min
+	}
+	tt.nextReg += mclock.AbsTime(registerFrequency)
+	s.tickets[topic] = tt
+
+	s.removeTicketRef(t)
+}
+
+// nextRegisterableTicket returns the next ticket that can be used
+// to register.
+//
+// If the returned wait time <= zero the ticket can be used. For a positive
+// wait time, the caller should requery the next ticket later.
+//
+// A ticket can be returned more than once with <= zero wait time in case
+// the ticket contains multiple topics.
+func (s *ticketStore) nextRegisterableTicket() (t *ticketRef, wait time.Duration) {
+	defer func() {
+		if t == nil {
+			debugLog(" nil")
+		} else {
+			debugLog(fmt.Sprintf(" node = %x sn = %v wait = %v", t.t.node.ID[:8], t.t.serial, wait))
+		}
+	}()
+
+	debugLog("nextRegisterableTicket()")
+	now := mclock.Now()
+	if s.nextTicketCached != nil {
+		return s.nextTicketCached, time.Duration(s.nextTicketCached.topicRegTime() - now)
+	}
+
+	for bucket := s.lastBucketFetched; ; bucket++ {
+		var (
+			empty      = true    // true if there are no tickets
+			nextTicket ticketRef // uninitialized if this bucket is empty
+		)
+		for _, tickets := range s.tickets {
+			//s.removeExcessTickets(topic)
+			if len(tickets.buckets) != 0 {
+				empty = false
+				if list := tickets.buckets[bucket]; list != nil {
+					for _, ref := range list {
+						//debugLog(fmt.Sprintf(" nrt bucket = %d node = %x sn = %v wait = %v", bucket, ref.t.node.ID[:8], ref.t.serial, time.Duration(ref.topicRegTime()-now)))
+						if nextTicket.t == nil || ref.topicRegTime() < nextTicket.topicRegTime() {
+							nextTicket = ref
+						}
+					}
+				}
+			}
+		}
+		if empty {
+			return nil, 0
+		}
+		if nextTicket.t != nil {
+			wait = time.Duration(nextTicket.topicRegTime() - now)
+			s.nextTicketCached = &nextTicket
+			return &nextTicket, wait
+		}
+		s.lastBucketFetched = bucket
+	}
+}
+
+// removeTicket removes a ticket from the ticket store
+func (s *ticketStore) removeTicketRef(ref ticketRef) {
+	debugLog(fmt.Sprintf("removeTicketRef(node = %x sn = %v)", ref.t.node.ID[:8], ref.t.serial))
+	topic := ref.topic()
+	tickets := s.tickets[topic].buckets
+	if tickets == nil {
+		return
+	}
+	bucket := timeBucket(ref.t.regTime[ref.idx] / mclock.AbsTime(ticketTimeBucketLen))
+	list := tickets[bucket]
+	idx := -1
+	for i, bt := range list {
+		if bt.t == ref.t {
+			idx = i
+			break
+		}
+	}
+	if idx == -1 {
+		panic(nil)
+	}
+	list = append(list[:idx], list[idx+1:]...)
+	if len(list) != 0 {
+		tickets[bucket] = list
+	} else {
+		delete(tickets, bucket)
+	}
+	ref.t.refCnt--
+	if ref.t.refCnt == 0 {
+		delete(s.nodes, ref.t.node)
+		delete(s.nodeLastReq, ref.t.node)
+	}
+
+	// Make nextRegisterableTicket return the next available ticket.
+	s.nextTicketCached = nil
+}
+
+type lookupInfo struct {
+	target       common.Hash
+	topic        Topic
+	radiusLookup bool
+}
+
+type reqInfo struct {
+	pingHash []byte
+	lookup   lookupInfo
+	time     mclock.AbsTime
+}
+
+// returns -1 if not found
+func (t *ticket) findIdx(topic Topic) int {
+	for i, tt := range t.topics {
+		if tt == topic {
+			return i
+		}
+	}
+	return -1
+}
+
+func (s *ticketStore) registerLookupDone(lookup lookupInfo, nodes []*Node, ping func(n *Node) []byte) {
+	now := mclock.Now()
+	for i, n := range nodes {
+		if i == 0 || (binary.BigEndian.Uint64(n.sha[:8])^binary.BigEndian.Uint64(lookup.target[:8])) < s.radius[lookup.topic].minRadius {
+			if lookup.radiusLookup {
+				if lastReq, ok := s.nodeLastReq[n]; !ok || time.Duration(now-lastReq.time) > radiusTC {
+					s.nodeLastReq[n] = reqInfo{pingHash: ping(n), lookup: lookup, time: now}
+				}
+			} else {
+				if s.nodes[n] == nil {
+					s.nodeLastReq[n] = reqInfo{pingHash: ping(n), lookup: lookup, time: now}
+				}
+			}
+		}
+	}
+}
+
+func (s *ticketStore) searchLookupDone(lookup lookupInfo, nodes []*Node, ping func(n *Node) []byte, query func(n *Node, topic Topic) []byte) {
+	now := mclock.Now()
+	for i, n := range nodes {
+		if i == 0 || (binary.BigEndian.Uint64(n.sha[:8])^binary.BigEndian.Uint64(lookup.target[:8])) < s.radius[lookup.topic].minRadius {
+			if lookup.radiusLookup {
+				if lastReq, ok := s.nodeLastReq[n]; !ok || time.Duration(now-lastReq.time) > radiusTC {
+					s.nodeLastReq[n] = reqInfo{pingHash: ping(n), lookup: lookup, time: now}
+				}
+			} // else {
+			if s.canQueryTopic(n, lookup.topic) {
+				hash := query(n, lookup.topic)
+				s.addTopicQuery(common.BytesToHash(hash), n, lookup)
+			}
+			//}
+		}
+	}
+}
+
+func (s *ticketStore) adjustWithTicket(now mclock.AbsTime, targetHash common.Hash, t *ticket) {
+	for i, topic := range t.topics {
+		if tt, ok := s.radius[topic]; ok {
+			tt.adjustWithTicket(now, targetHash, ticketRef{t, i})
+		}
+	}
+}
+
+func (s *ticketStore) addTicket(localTime mclock.AbsTime, pingHash []byte, t *ticket) {
+	debugLog(fmt.Sprintf("add(node = %x sn = %v)", t.node.ID[:8], t.serial))
+
+	lastReq, ok := s.nodeLastReq[t.node]
+	if !(ok && bytes.Equal(pingHash, lastReq.pingHash)) {
+		return
+	}
+	s.adjustWithTicket(localTime, lastReq.lookup.target, t)
+
+	if lastReq.lookup.radiusLookup || s.nodes[t.node] != nil {
+		return
+	}
+
+	topic := lastReq.lookup.topic
+	topicIdx := t.findIdx(topic)
+	if topicIdx == -1 {
+		return
+	}
+
+	bucket := timeBucket(localTime / mclock.AbsTime(ticketTimeBucketLen))
+	if s.lastBucketFetched == 0 || bucket < s.lastBucketFetched {
+		s.lastBucketFetched = bucket
+	}
+
+	if _, ok := s.tickets[topic]; ok {
+		wait := t.regTime[topicIdx] - localTime
+		rnd := rand.ExpFloat64()
+		if rnd > 10 {
+			rnd = 10
+		}
+		if float64(wait) < float64(keepTicketConst)+float64(keepTicketExp)*rnd {
+			// use the ticket to register this topic
+			//fmt.Println("addTicket", t.node.ID[:8], t.node.addr().String(), t.serial, t.pong)
+			s.addTicketRef(ticketRef{t, topicIdx})
+		}
+	}
+
+	if t.refCnt > 0 {
+		s.nextTicketCached = nil
+		s.nodes[t.node] = t
+	}
+}
+
+func (s *ticketStore) getNodeTicket(node *Node) *ticket {
+	if s.nodes[node] == nil {
+		debugLog(fmt.Sprintf("getNodeTicket(%x) sn = nil", node.ID[:8]))
+	} else {
+		debugLog(fmt.Sprintf("getNodeTicket(%x) sn = %v", node.ID[:8], s.nodes[node].serial))
+	}
+	return s.nodes[node]
+}
+
+func (s *ticketStore) canQueryTopic(node *Node, topic Topic) bool {
+	qq := s.queriesSent[node]
+	if qq != nil {
+		now := mclock.Now()
+		for _, sq := range qq {
+			if sq.lookup.topic == topic && sq.sent > now-mclock.AbsTime(topicQueryResend) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func (s *ticketStore) addTopicQuery(hash common.Hash, node *Node, lookup lookupInfo) {
+	now := mclock.Now()
+	qq := s.queriesSent[node]
+	if qq == nil {
+		qq = make(map[common.Hash]sentQuery)
+		s.queriesSent[node] = qq
+	}
+	qq[hash] = sentQuery{sent: now, lookup: lookup}
+	s.cleanupTopicQueries(now)
+}
+
+func (s *ticketStore) cleanupTopicQueries(now mclock.AbsTime) {
+	if s.nextTopicQueryCleanup > now {
+		return
+	}
+	exp := now - mclock.AbsTime(topicQueryResend)
+	for n, qq := range s.queriesSent {
+		for h, q := range qq {
+			if q.sent < exp {
+				delete(qq, h)
+			}
+		}
+		if len(qq) == 0 {
+			delete(s.queriesSent, n)
+		}
+	}
+	s.nextTopicQueryCleanup = now + mclock.AbsTime(topicQueryTimeout)
+}
+
+func (s *ticketStore) gotTopicNodes(from *Node, hash common.Hash, nodes []rpcNode) (timeout bool) {
+	now := mclock.Now()
+	//fmt.Println("got", from.addr().String(), hash, len(nodes))
+	qq := s.queriesSent[from]
+	if qq == nil {
+		return true
+	}
+	q, ok := qq[hash]
+	if !ok || now > q.sent+mclock.AbsTime(topicQueryTimeout) {
+		return true
+	}
+	inside := float64(0)
+	if len(nodes) > 0 {
+		inside = 1
+	}
+	s.radius[q.lookup.topic].adjust(now, q.lookup.target, from.sha, inside)
+	chn := s.searchTopicMap[q.lookup.topic].foundChn
+	if chn == nil {
+		//fmt.Println("no channel")
+		return false
+	}
+	for _, node := range nodes {
+		ip := node.IP
+		if ip.IsUnspecified() || ip.IsLoopback() {
+			ip = from.IP
+		}
+		enode := NewNode(node.ID, ip, node.UDP-1, node.TCP-1).String() // subtract one from port while discv5 is running in test mode on UDPport+1
+		select {
+		case chn <- enode:
+		default:
+			return false
+		}
+	}
+	return false
+}
+
+type topicRadius struct {
+	topic             Topic
+	topicHashPrefix   uint64
+	radius, minRadius uint64
+	buckets           []topicRadiusBucket
+}
+
+type topicRadiusEvent int
+
+const (
+	trOutside topicRadiusEvent = iota
+	trInside
+	trNoAdjust
+	trCount
+)
+
+type topicRadiusBucket struct {
+	weights    [trCount]float64
+	lastTime   mclock.AbsTime
+	value      float64
+	lookupSent map[common.Hash]mclock.AbsTime
+}
+
+func (b *topicRadiusBucket) update(now mclock.AbsTime) {
+	if now == b.lastTime {
+		return
+	}
+	exp := math.Exp(-float64(now-b.lastTime) / float64(radiusTC))
+	for i, w := range b.weights {
+		b.weights[i] = w * exp
+	}
+	b.lastTime = now
+
+	for target, tm := range b.lookupSent {
+		if now-tm > mclock.AbsTime(pingTimeout) {
+			b.weights[trNoAdjust] += 1
+			delete(b.lookupSent, target)
+		}
+	}
+}
+
+func (b *topicRadiusBucket) adjust(now mclock.AbsTime, inside float64) {
+	b.update(now)
+	if inside <= 0 {
+		b.weights[trOutside] += 1
+	} else {
+		if inside >= 1 {
+			b.weights[trInside] += 1
+		} else {
+			b.weights[trInside] += inside
+			b.weights[trOutside] += 1 - inside
+		}
+	}
+}
+
+func newTopicRadius(t Topic) *topicRadius {
+	topicHash := crypto.Keccak256Hash([]byte(t))
+	topicHashPrefix := binary.BigEndian.Uint64(topicHash[0:8])
+
+	return &topicRadius{
+		topic:           t,
+		topicHashPrefix: topicHashPrefix,
+		radius:          maxRadius,
+		minRadius:       maxRadius,
+	}
+}
+
+func (r *topicRadius) getBucketIdx(addrHash common.Hash) int {
+	prefix := binary.BigEndian.Uint64(addrHash[0:8])
+	var log2 float64
+	if prefix != r.topicHashPrefix {
+		log2 = math.Log2(float64(prefix ^ r.topicHashPrefix))
+	}
+	bucket := int((64 - log2) * radiusBucketsPerBit)
+	max := 64*radiusBucketsPerBit - 1
+	if bucket > max {
+		return max
+	}
+	if bucket < 0 {
+		return 0
+	}
+	return bucket
+}
+
+func (r *topicRadius) targetForBucket(bucket int) common.Hash {
+	min := math.Pow(2, 64-float64(bucket+1)/radiusBucketsPerBit)
+	max := math.Pow(2, 64-float64(bucket)/radiusBucketsPerBit)
+	a := uint64(min)
+	b := randUint64n(uint64(max - min))
+	xor := a + b
+	if xor < a {
+		xor = ^uint64(0)
+	}
+	prefix := r.topicHashPrefix ^ xor
+	var target common.Hash
+	binary.BigEndian.PutUint64(target[0:8], prefix)
+	rand.Read(target[8:])
+	return target
+}
+
+func (r *topicRadius) isInRadius(addrHash common.Hash) bool {
+	nodePrefix := binary.BigEndian.Uint64(addrHash[0:8])
+	dist := nodePrefix ^ r.topicHashPrefix
+	return dist < r.radius
+}
+
+func (r *topicRadius) chooseLookupBucket(a, b int) int {
+	if a < 0 {
+		a = 0
+	}
+	if a > b {
+		return -1
+	}
+	c := 0
+	for i := a; i <= b; i++ {
+		if i >= len(r.buckets) || r.buckets[i].weights[trNoAdjust] < maxNoAdjust {
+			c++
+		}
+	}
+	if c == 0 {
+		return -1
+	}
+	rnd := randUint(uint32(c))
+	for i := a; i <= b; i++ {
+		if i >= len(r.buckets) || r.buckets[i].weights[trNoAdjust] < maxNoAdjust {
+			if rnd == 0 {
+				return i
+			}
+			rnd--
+		}
+	}
+	panic(nil) // should never happen
+}
+
+func (r *topicRadius) needMoreLookups(a, b int, maxValue float64) bool {
+	var max float64
+	if a < 0 {
+		a = 0
+	}
+	if b >= len(r.buckets) {
+		b = len(r.buckets) - 1
+		if r.buckets[b].value > max {
+			max = r.buckets[b].value
+		}
+	}
+	if b >= a {
+		for i := a; i <= b; i++ {
+			if r.buckets[i].value > max {
+				max = r.buckets[i].value
+			}
+		}
+	}
+	return maxValue-max < minPeakSize
+}
+
+func (r *topicRadius) recalcRadius() (radius uint64, radiusLookup int) {
+	maxBucket := 0
+	maxValue := float64(0)
+	now := mclock.Now()
+	v := float64(0)
+	for i, _ := range r.buckets {
+		r.buckets[i].update(now)
+		v += r.buckets[i].weights[trOutside] - r.buckets[i].weights[trInside]
+		r.buckets[i].value = v
+		//fmt.Printf("%v %v | ", v, r.buckets[i].weights[trNoAdjust])
+	}
+	//fmt.Println()
+	slopeCross := -1
+	for i, b := range r.buckets {
+		v := b.value
+		if v < float64(i)*minSlope {
+			slopeCross = i
+			break
+		}
+		if v > maxValue {
+			maxValue = v
+			maxBucket = i + 1
+		}
+	}
+
+	minRadBucket := len(r.buckets)
+	sum := float64(0)
+	for minRadBucket > 0 && sum < minRightSum {
+		minRadBucket--
+		b := r.buckets[minRadBucket]
+		sum += b.weights[trInside] + b.weights[trOutside]
+	}
+	r.minRadius = uint64(math.Pow(2, 64-float64(minRadBucket)/radiusBucketsPerBit))
+
+	lookupLeft := -1
+	if r.needMoreLookups(0, maxBucket-lookupWidth-1, maxValue) {
+		lookupLeft = r.chooseLookupBucket(maxBucket-lookupWidth, maxBucket-1)
+	}
+	lookupRight := -1
+	if slopeCross != maxBucket && (minRadBucket <= maxBucket || r.needMoreLookups(maxBucket+lookupWidth, len(r.buckets)-1, maxValue)) {
+		for len(r.buckets) <= maxBucket+lookupWidth {
+			r.buckets = append(r.buckets, topicRadiusBucket{lookupSent: make(map[common.Hash]mclock.AbsTime)})
+		}
+		lookupRight = r.chooseLookupBucket(maxBucket, maxBucket+lookupWidth-1)
+	}
+	if lookupLeft == -1 {
+		radiusLookup = lookupRight
+	} else {
+		if lookupRight == -1 {
+			radiusLookup = lookupLeft
+		} else {
+			if randUint(2) == 0 {
+				radiusLookup = lookupLeft
+			} else {
+				radiusLookup = lookupRight
+			}
+		}
+	}
+
+	//fmt.Println("mb", maxBucket, "sc", slopeCross, "mrb", minRadBucket, "ll", lookupLeft, "lr", lookupRight, "mv", maxValue)
+
+	if radiusLookup == -1 {
+		// no more radius lookups needed at the moment, return a radius
+		rad := maxBucket
+		if minRadBucket < rad {
+			rad = minRadBucket
+		}
+		radius = ^uint64(0)
+		if rad > 0 {
+			radius = uint64(math.Pow(2, 64-float64(rad)/radiusBucketsPerBit))
+		}
+		r.radius = radius
+	}
+
+	return
+}
+
+func (r *topicRadius) nextTarget(forceRegular bool) lookupInfo {
+	if !forceRegular {
+		_, radiusLookup := r.recalcRadius()
+		if radiusLookup != -1 {
+			target := r.targetForBucket(radiusLookup)
+			r.buckets[radiusLookup].lookupSent[target] = mclock.Now()
+			return lookupInfo{target: target, topic: r.topic, radiusLookup: true}
+		}
+	}
+
+	radExt := r.radius / 2
+	if radExt > maxRadius-r.radius {
+		radExt = maxRadius - r.radius
+	}
+	rnd := randUint64n(r.radius) + randUint64n(2*radExt)
+	if rnd > radExt {
+		rnd -= radExt
+	} else {
+		rnd = radExt - rnd
+	}
+
+	prefix := r.topicHashPrefix ^ rnd
+	var target common.Hash
+	binary.BigEndian.PutUint64(target[0:8], prefix)
+	rand.Read(target[8:])
+	return lookupInfo{target: target, topic: r.topic, radiusLookup: false}
+}
+
+func (r *topicRadius) adjustWithTicket(now mclock.AbsTime, targetHash common.Hash, t ticketRef) {
+	wait := t.t.regTime[t.idx] - t.t.issueTime
+	inside := float64(wait)/float64(targetWaitTime) - 0.5
+	if inside > 1 {
+		inside = 1
+	}
+	if inside < 0 {
+		inside = 0
+	}
+	r.adjust(now, targetHash, t.t.node.sha, inside)
+}
+
+func (r *topicRadius) adjust(now mclock.AbsTime, targetHash, addrHash common.Hash, inside float64) {
+	bucket := r.getBucketIdx(addrHash)
+	//fmt.Println("adjust", bucket, len(r.buckets), inside)
+	if bucket >= len(r.buckets) {
+		return
+	}
+	r.buckets[bucket].adjust(now, inside)
+	delete(r.buckets[bucket].lookupSent, targetHash)
+}
diff --git a/p2p/discv5/topic.go b/p2p/discv5/topic.go
new file mode 100644
index 000000000..e603cf7e4
--- /dev/null
+++ b/p2p/discv5/topic.go
@@ -0,0 +1,406 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"container/heap"
+	"fmt"
+	"math"
+	"math/rand"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+const (
+	maxEntries         = 10000
+	maxEntriesPerTopic = 50
+
+	fallbackRegistrationExpiry = 1 * time.Hour
+)
+
+type Topic string
+
+type topicEntry struct {
+	topic   Topic
+	fifoIdx uint64
+	node    *Node
+	expire  mclock.AbsTime
+}
+
+type topicInfo struct {
+	entries            map[uint64]*topicEntry
+	fifoHead, fifoTail uint64
+	rqItem             *topicRequestQueueItem
+	wcl                waitControlLoop
+}
+
+// removes tail element from the fifo
+func (t *topicInfo) getFifoTail() *topicEntry {
+	for t.entries[t.fifoTail] == nil {
+		t.fifoTail++
+	}
+	tail := t.entries[t.fifoTail]
+	t.fifoTail++
+	return tail
+}
+
+type nodeInfo struct {
+	entries                          map[Topic]*topicEntry
+	lastIssuedTicket, lastUsedTicket uint32
+	// you can't register a ticket newer than lastUsedTicket before noRegUntil (absolute time)
+	noRegUntil mclock.AbsTime
+}
+
+type topicTable struct {
+	db                    *nodeDB
+	self                  *Node
+	nodes                 map[*Node]*nodeInfo
+	topics                map[Topic]*topicInfo
+	globalEntries         uint64
+	requested             topicRequestQueue
+	requestCnt            uint64
+	lastGarbageCollection mclock.AbsTime
+}
+
+func newTopicTable(db *nodeDB, self *Node) *topicTable {
+	if printTestImgLogs {
+		fmt.Printf("*N %016x\n", self.sha[:8])
+	}
+	return &topicTable{
+		db:     db,
+		nodes:  make(map[*Node]*nodeInfo),
+		topics: make(map[Topic]*topicInfo),
+		self:   self,
+	}
+}
+
+func (t *topicTable) getOrNewTopic(topic Topic) *topicInfo {
+	ti := t.topics[topic]
+	if ti == nil {
+		rqItem := &topicRequestQueueItem{
+			topic:    topic,
+			priority: t.requestCnt,
+		}
+		ti = &topicInfo{
+			entries: make(map[uint64]*topicEntry),
+			rqItem:  rqItem,
+		}
+		t.topics[topic] = ti
+		heap.Push(&t.requested, rqItem)
+	}
+	return ti
+}
+
+func (t *topicTable) checkDeleteTopic(topic Topic) {
+	ti := t.topics[topic]
+	if ti == nil {
+		return
+	}
+	if len(ti.entries) == 0 && ti.wcl.hasMinimumWaitPeriod() {
+		delete(t.topics, topic)
+		heap.Remove(&t.requested, ti.rqItem.index)
+	}
+}
+
+func (t *topicTable) getOrNewNode(node *Node) *nodeInfo {
+	n := t.nodes[node]
+	if n == nil {
+		//fmt.Printf("newNode %016x %016x\n", t.self.sha[:8], node.sha[:8])
+		var issued, used uint32
+		if t.db != nil {
+			issued, used = t.db.fetchTopicRegTickets(node.ID)
+		}
+		n = &nodeInfo{
+			entries:          make(map[Topic]*topicEntry),
+			lastIssuedTicket: issued,
+			lastUsedTicket:   used,
+		}
+		t.nodes[node] = n
+	}
+	return n
+}
+
+func (t *topicTable) checkDeleteNode(node *Node) {
+	if n, ok := t.nodes[node]; ok && len(n.entries) == 0 && n.noRegUntil < mclock.Now() {
+		//fmt.Printf("deleteNode %016x %016x\n", t.self.sha[:8], node.sha[:8])
+		delete(t.nodes, node)
+	}
+}
+
+func (t *topicTable) storeTicketCounters(node *Node) {
+	n := t.getOrNewNode(node)
+	if t.db != nil {
+		t.db.updateTopicRegTickets(node.ID, n.lastIssuedTicket, n.lastUsedTicket)
+	}
+}
+
+func (t *topicTable) getEntries(topic Topic) []*Node {
+	t.collectGarbage()
+
+	te := t.topics[topic]
+	if te == nil {
+		return nil
+	}
+	nodes := make([]*Node, len(te.entries))
+	i := 0
+	for _, e := range te.entries {
+		nodes[i] = e.node
+		i++
+	}
+	t.requestCnt++
+	t.requested.update(te.rqItem, t.requestCnt)
+	return nodes
+}
+
+func (t *topicTable) addEntry(node *Node, topic Topic) {
+	n := t.getOrNewNode(node)
+	// clear previous entries by the same node
+	for _, e := range n.entries {
+		t.deleteEntry(e)
+	}
+	// ***
+	n = t.getOrNewNode(node)
+
+	tm := mclock.Now()
+	te := t.getOrNewTopic(topic)
+
+	if len(te.entries) == maxEntriesPerTopic {
+		t.deleteEntry(te.getFifoTail())
+	}
+
+	if t.globalEntries == maxEntries {
+		t.deleteEntry(t.leastRequested()) // not empty, no need to check for nil
+	}
+
+	fifoIdx := te.fifoHead
+	te.fifoHead++
+	entry := &topicEntry{
+		topic:   topic,
+		fifoIdx: fifoIdx,
+		node:    node,
+		expire:  tm + mclock.AbsTime(fallbackRegistrationExpiry),
+	}
+	if printTestImgLogs {
+		fmt.Printf("*+ %d %v %016x %016x\n", tm/1000000, topic, t.self.sha[:8], node.sha[:8])
+	}
+	te.entries[fifoIdx] = entry
+	n.entries[topic] = entry
+	t.globalEntries++
+	te.wcl.registered(tm)
+}
+
+// removes least requested element from the fifo
+func (t *topicTable) leastRequested() *topicEntry {
+	for t.requested.Len() > 0 && t.topics[t.requested[0].topic] == nil {
+		heap.Pop(&t.requested)
+	}
+	if t.requested.Len() == 0 {
+		return nil
+	}
+	return t.topics[t.requested[0].topic].getFifoTail()
+}
+
+// entry should exist
+func (t *topicTable) deleteEntry(e *topicEntry) {
+	if printTestImgLogs {
+		fmt.Printf("*- %d %v %016x %016x\n", mclock.Now()/1000000, e.topic, t.self.sha[:8], e.node.sha[:8])
+	}
+	ne := t.nodes[e.node].entries
+	delete(ne, e.topic)
+	if len(ne) == 0 {
+		t.checkDeleteNode(e.node)
+	}
+	te := t.topics[e.topic]
+	delete(te.entries, e.fifoIdx)
+	if len(te.entries) == 0 {
+		t.checkDeleteTopic(e.topic)
+	}
+	t.globalEntries--
+}
+
+// It is assumed that topics and waitPeriods have the same length.
+func (t *topicTable) useTicket(node *Node, serialNo uint32, topics []Topic, idx int, issueTime uint64, waitPeriods []uint32) (registered bool) {
+	debugLog(fmt.Sprintf("useTicket %v %v %v", serialNo, topics, waitPeriods))
+	//fmt.Println("useTicket", serialNo, topics, waitPeriods)
+	t.collectGarbage()
+
+	n := t.getOrNewNode(node)
+	if serialNo < n.lastUsedTicket {
+		return false
+	}
+
+	tm := mclock.Now()
+	if serialNo > n.lastUsedTicket && tm < n.noRegUntil {
+		return false
+	}
+	if serialNo != n.lastUsedTicket {
+		n.lastUsedTicket = serialNo
+		n.noRegUntil = tm + mclock.AbsTime(noRegTimeout())
+		t.storeTicketCounters(node)
+	}
+
+	currTime := uint64(tm / mclock.AbsTime(time.Second))
+	regTime := issueTime + uint64(waitPeriods[idx])
+	relTime := int64(currTime - regTime)
+	if relTime >= -1 && relTime <= regTimeWindow+1 { // give clients a little security margin on both ends
+		if e := n.entries[topics[idx]]; e == nil {
+			t.addEntry(node, topics[idx])
+		} else {
+			// if there is an active entry, don't move to the front of the FIFO but prolong expire time
+			e.expire = tm + mclock.AbsTime(fallbackRegistrationExpiry)
+		}
+		return true
+	}
+
+	return false
+}
+
+func (topictab *topicTable) getTicket(node *Node, topics []Topic) *ticket {
+	topictab.collectGarbage()
+
+	now := mclock.Now()
+	n := topictab.getOrNewNode(node)
+	n.lastIssuedTicket++
+	topictab.storeTicketCounters(node)
+
+	t := &ticket{
+		issueTime: now,
+		topics:    topics,
+		serial:    n.lastIssuedTicket,
+		regTime:   make([]mclock.AbsTime, len(topics)),
+	}
+	for i, topic := range topics {
+		var waitPeriod time.Duration
+		if topic := topictab.topics[topic]; topic != nil {
+			waitPeriod = topic.wcl.waitPeriod
+		} else {
+			waitPeriod = minWaitPeriod
+		}
+
+		t.regTime[i] = now + mclock.AbsTime(waitPeriod)
+	}
+	return t
+}
+
+const gcInterval = time.Minute
+
+func (t *topicTable) collectGarbage() {
+	tm := mclock.Now()
+	if time.Duration(tm-t.lastGarbageCollection) < gcInterval {
+		return
+	}
+	t.lastGarbageCollection = tm
+
+	for node, n := range t.nodes {
+		for _, e := range n.entries {
+			if e.expire <= tm {
+				t.deleteEntry(e)
+			}
+		}
+
+		t.checkDeleteNode(node)
+	}
+
+	for topic, _ := range t.topics {
+		t.checkDeleteTopic(topic)
+	}
+}
+
+const (
+	minWaitPeriod   = time.Minute
+	regTimeWindow   = 10 // seconds
+	avgnoRegTimeout = time.Minute * 10
+	// target average interval between two incoming ad requests
+	wcTargetRegInterval = time.Minute * 10 / maxEntriesPerTopic
+	//
+	wcTimeConst = time.Minute * 10
+)
+
+// initialization is not required, will set to minWaitPeriod at first registration
+type waitControlLoop struct {
+	lastIncoming mclock.AbsTime
+	waitPeriod   time.Duration
+}
+
+func (w *waitControlLoop) registered(tm mclock.AbsTime) {
+	w.waitPeriod = w.nextWaitPeriod(tm)
+	w.lastIncoming = tm
+}
+
+func (w *waitControlLoop) nextWaitPeriod(tm mclock.AbsTime) time.Duration {
+	period := tm - w.lastIncoming
+	wp := time.Duration(float64(w.waitPeriod) * math.Exp((float64(wcTargetRegInterval)-float64(period))/float64(wcTimeConst)))
+	if wp < minWaitPeriod {
+		wp = minWaitPeriod
+	}
+	return wp
+}
+
+func (w *waitControlLoop) hasMinimumWaitPeriod() bool {
+	return w.nextWaitPeriod(mclock.Now()) == minWaitPeriod
+}
+
+func noRegTimeout() time.Duration {
+	e := rand.ExpFloat64()
+	if e > 100 {
+		e = 100
+	}
+	return time.Duration(float64(avgnoRegTimeout) * e)
+}
+
+type topicRequestQueueItem struct {
+	topic    Topic
+	priority uint64
+	index    int
+}
+
+// A topicRequestQueue implements heap.Interface and holds topicRequestQueueItems.
+type topicRequestQueue []*topicRequestQueueItem
+
+func (tq topicRequestQueue) Len() int { return len(tq) }
+
+func (tq topicRequestQueue) Less(i, j int) bool {
+	return tq[i].priority < tq[j].priority
+}
+
+func (tq topicRequestQueue) Swap(i, j int) {
+	tq[i], tq[j] = tq[j], tq[i]
+	tq[i].index = i
+	tq[j].index = j
+}
+
+func (tq *topicRequestQueue) Push(x interface{}) {
+	n := len(*tq)
+	item := x.(*topicRequestQueueItem)
+	item.index = n
+	*tq = append(*tq, item)
+}
+
+func (tq *topicRequestQueue) Pop() interface{} {
+	old := *tq
+	n := len(old)
+	item := old[n-1]
+	item.index = -1
+	*tq = old[0 : n-1]
+	return item
+}
+
+func (tq *topicRequestQueue) update(item *topicRequestQueueItem, priority uint64) {
+	item.priority = priority
+	heap.Fix(tq, item.index)
+}
diff --git a/p2p/discv5/topic_test.go b/p2p/discv5/topic_test.go
new file mode 100644
index 000000000..f29df1638
--- /dev/null
+++ b/p2p/discv5/topic_test.go
@@ -0,0 +1,71 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"encoding/binary"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/mclock"
+)
+
+func TestTopicRadius(t *testing.T) {
+	now := mclock.Now()
+	topic := Topic("qwerty")
+	rad := newTopicRadius(topic)
+	targetRad := (^uint64(0)) / 100
+
+	waitFn := func(addr common.Hash) time.Duration {
+		prefix := binary.BigEndian.Uint64(addr[0:8])
+		dist := prefix ^ rad.topicHashPrefix
+		relDist := float64(dist) / float64(targetRad)
+		relTime := (1 - relDist/2) * 2
+		if relTime < 0 {
+			relTime = 0
+		}
+		return time.Duration(float64(targetWaitTime) * relTime)
+	}
+
+	bcnt := 0
+	cnt := 0
+	var sum float64
+	for cnt < 100 {
+		addr := rad.nextTarget(false).target
+		wait := waitFn(addr)
+		ticket := &ticket{
+			topics:  []Topic{topic},
+			regTime: []mclock.AbsTime{mclock.AbsTime(wait)},
+			node:    &Node{nodeNetGuts: nodeNetGuts{sha: addr}},
+		}
+		rad.adjustWithTicket(now, addr, ticketRef{ticket, 0})
+		if rad.radius != maxRadius {
+			cnt++
+			sum += float64(rad.radius)
+		} else {
+			bcnt++
+			if bcnt > 500 {
+				t.Errorf("Radius did not converge in 500 iterations")
+			}
+		}
+	}
+	avgRel := sum / float64(cnt) / float64(targetRad)
+	if avgRel > 1.05 || avgRel < 0.95 {
+		t.Errorf("Average/target ratio is too far from 1 (%v)", avgRel)
+	}
+}
diff --git a/p2p/discv5/udp.go b/p2p/discv5/udp.go
new file mode 100644
index 000000000..328d94ef7
--- /dev/null
+++ b/p2p/discv5/udp.go
@@ -0,0 +1,456 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"errors"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/logger"
+	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/p2p/nat"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+const Version = 4
+
+// Errors
+var (
+	errPacketTooSmall   = errors.New("too small")
+	errBadHash          = errors.New("bad hash")
+	errExpired          = errors.New("expired")
+	errUnsolicitedReply = errors.New("unsolicited reply")
+	errUnknownNode      = errors.New("unknown node")
+	errTimeout          = errors.New("RPC timeout")
+	errClockWarp        = errors.New("reply deadline too far in the future")
+	errClosed           = errors.New("socket closed")
+)
+
+// Timeouts
+const (
+	respTimeout = 500 * time.Millisecond
+	sendTimeout = 500 * time.Millisecond
+	expiration  = 20 * time.Second
+
+	ntpFailureThreshold = 32               // Continuous timeouts after which to check NTP
+	ntpWarningCooldown  = 10 * time.Minute // Minimum amount of time to pass before repeating NTP warning
+	driftThreshold      = 10 * time.Second // Allowed clock drift before warning user
+)
+
+// RPC request structures
+type (
+	ping struct {
+		Version    uint
+		From, To   rpcEndpoint
+		Expiration uint64
+
+		// v5
+		Topics []Topic
+
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// pong is the reply to ping.
+	pong struct {
+		// This field should mirror the UDP envelope address
+		// of the ping packet, which provides a way to discover the
+		// the external address (after NAT).
+		To rpcEndpoint
+
+		ReplyTok   []byte // This contains the hash of the ping packet.
+		Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
+
+		// v5
+		TopicHash    common.Hash
+		TicketSerial uint32
+		WaitPeriods  []uint32
+
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// findnode is a query for nodes close to the given target.
+	findnode struct {
+		Target     NodeID // doesn't need to be an actual public key
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// findnode is a query for nodes close to the given target.
+	findnodeHash struct {
+		Target     common.Hash
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	// reply to findnode
+	neighbors struct {
+		Nodes      []rpcNode
+		Expiration uint64
+		// Ignore additional fields (for forward compatibility).
+		Rest []rlp.RawValue `rlp:"tail"`
+	}
+
+	topicRegister struct {
+		Topics []Topic
+		Idx    uint
+		Pong   []byte
+	}
+
+	topicQuery struct {
+		Topic      Topic
+		Expiration uint64
+	}
+
+	// reply to topicQuery
+	topicNodes struct {
+		Echo  common.Hash
+		Nodes []rpcNode
+	}
+
+	rpcNode struct {
+		IP  net.IP // len 4 for IPv4 or 16 for IPv6
+		UDP uint16 // for discovery protocol
+		TCP uint16 // for RLPx protocol
+		ID  NodeID
+	}
+
+	rpcEndpoint struct {
+		IP  net.IP // len 4 for IPv4 or 16 for IPv6
+		UDP uint16 // for discovery protocol
+		TCP uint16 // for RLPx protocol
+	}
+)
+
+const (
+	macSize  = 256 / 8
+	sigSize  = 520 / 8
+	headSize = macSize + sigSize // space of packet frame data
+)
+
+// Neighbors replies are sent across multiple packets to
+// stay below the 1280 byte limit. We compute the maximum number
+// of entries by stuffing a packet until it grows too large.
+var maxNeighbors = func() int {
+	p := neighbors{Expiration: ^uint64(0)}
+	maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
+	for n := 0; ; n++ {
+		p.Nodes = append(p.Nodes, maxSizeNode)
+		size, _, err := rlp.EncodeToReader(p)
+		if err != nil {
+			// If this ever happens, it will be caught by the unit tests.
+			panic("cannot encode: " + err.Error())
+		}
+		if headSize+size+1 >= 1280 {
+			return n
+		}
+	}
+}()
+
+var maxTopicNodes = func() int {
+	p := topicNodes{}
+	maxSizeNode := rpcNode{IP: make(net.IP, 16), UDP: ^uint16(0), TCP: ^uint16(0)}
+	for n := 0; ; n++ {
+		p.Nodes = append(p.Nodes, maxSizeNode)
+		size, _, err := rlp.EncodeToReader(p)
+		if err != nil {
+			// If this ever happens, it will be caught by the unit tests.
+			panic("cannot encode: " + err.Error())
+		}
+		if headSize+size+1 >= 1280 {
+			return n
+		}
+	}
+}()
+
+func makeEndpoint(addr *net.UDPAddr, tcpPort uint16) rpcEndpoint {
+	ip := addr.IP.To4()
+	if ip == nil {
+		ip = addr.IP.To16()
+	}
+	return rpcEndpoint{IP: ip, UDP: uint16(addr.Port), TCP: tcpPort}
+}
+
+func (e1 rpcEndpoint) equal(e2 rpcEndpoint) bool {
+	return e1.UDP == e2.UDP && e1.TCP == e2.TCP && bytes.Equal(e1.IP, e2.IP)
+}
+
+func nodeFromRPC(rn rpcNode) (*Node, error) {
+	// TODO: don't accept localhost, LAN addresses from internet hosts
+	n := NewNode(rn.ID, rn.IP, rn.UDP, rn.TCP)
+	err := n.validateComplete()
+	return n, err
+}
+
+func nodeToRPC(n *Node) rpcNode {
+	return rpcNode{ID: n.ID, IP: n.IP, UDP: n.UDP, TCP: n.TCP}
+}
+
+type ingressPacket struct {
+	remoteID   NodeID
+	remoteAddr *net.UDPAddr
+	ev         nodeEvent
+	hash       []byte
+	data       interface{} // one of the RPC structs
+	rawData    []byte
+}
+
+type conn interface {
+	ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error)
+	WriteToUDP(b []byte, addr *net.UDPAddr) (n int, err error)
+	Close() error
+	LocalAddr() net.Addr
+}
+
+// udp implements the RPC protocol.
+type udp struct {
+	conn        conn
+	priv        *ecdsa.PrivateKey
+	ourEndpoint rpcEndpoint
+	nat         nat.Interface
+	net         *Network
+}
+
+// ListenUDP returns a new table that listens for UDP packets on laddr.
+func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Network, error) {
+	transport, err := listenUDP(priv, laddr)
+	if err != nil {
+		return nil, err
+	}
+	net, err := newNetwork(transport, priv.PublicKey, natm, nodeDBPath)
+	if err != nil {
+		return nil, err
+	}
+	transport.net = net
+	go transport.readLoop()
+	return net, nil
+}
+
+func listenUDP(priv *ecdsa.PrivateKey, laddr string) (*udp, error) {
+	addr, err := net.ResolveUDPAddr("udp", laddr)
+	if err != nil {
+		return nil, err
+	}
+	conn, err := net.ListenUDP("udp", addr)
+	if err != nil {
+		return nil, err
+	}
+	return &udp{conn: conn, priv: priv, ourEndpoint: makeEndpoint(addr, uint16(addr.Port))}, nil
+}
+
+func (t *udp) localAddr() *net.UDPAddr {
+	return t.conn.LocalAddr().(*net.UDPAddr)
+}
+
+func (t *udp) Close() {
+	t.conn.Close()
+}
+
+func (t *udp) send(remote *Node, ptype nodeEvent, data interface{}) (hash []byte) {
+	hash, _ = t.sendPacket(remote.ID, remote.addr(), byte(ptype), data)
+	return hash
+}
+
+func (t *udp) sendPing(remote *Node, toaddr *net.UDPAddr, topics []Topic) (hash []byte) {
+	hash, _ = t.sendPacket(remote.ID, toaddr, byte(pingPacket), ping{
+		Version:    Version,
+		From:       t.ourEndpoint,
+		To:         makeEndpoint(toaddr, uint16(toaddr.Port)), // TODO: maybe use known TCP port from DB
+		Expiration: uint64(time.Now().Add(expiration).Unix()),
+		Topics:     topics,
+	})
+	return hash
+}
+
+func (t *udp) sendFindnode(remote *Node, target NodeID) {
+	t.sendPacket(remote.ID, remote.addr(), byte(findnodePacket), findnode{
+		Target:     target,
+		Expiration: uint64(time.Now().Add(expiration).Unix()),
+	})
+}
+
+func (t *udp) sendNeighbours(remote *Node, results []*Node) {
+	// Send neighbors in chunks with at most maxNeighbors per packet
+	// to stay below the 1280 byte limit.
+	p := neighbors{Expiration: uint64(time.Now().Add(expiration).Unix())}
+	for i, result := range results {
+		p.Nodes = append(p.Nodes, nodeToRPC(result))
+		if len(p.Nodes) == maxNeighbors || i == len(results)-1 {
+			t.sendPacket(remote.ID, remote.addr(), byte(neighborsPacket), p)
+			p.Nodes = p.Nodes[:0]
+		}
+	}
+}
+
+func (t *udp) sendFindnodeHash(remote *Node, target common.Hash) {
+	t.sendPacket(remote.ID, remote.addr(), byte(findnodeHashPacket), findnodeHash{
+		Target:     target,
+		Expiration: uint64(time.Now().Add(expiration).Unix()),
+	})
+}
+
+func (t *udp) sendTopicRegister(remote *Node, topics []Topic, idx int, pong []byte) {
+	t.sendPacket(remote.ID, remote.addr(), byte(topicRegisterPacket), topicRegister{
+		Topics: topics,
+		Idx:    uint(idx),
+		Pong:   pong,
+	})
+}
+
+func (t *udp) sendTopicNodes(remote *Node, queryHash common.Hash, nodes []*Node) {
+	p := topicNodes{Echo: queryHash}
+	if len(nodes) == 0 {
+		t.sendPacket(remote.ID, remote.addr(), byte(topicNodesPacket), p)
+		return
+	}
+	for i, result := range nodes {
+		p.Nodes = append(p.Nodes, nodeToRPC(result))
+		if len(p.Nodes) == maxTopicNodes || i == len(nodes)-1 {
+			t.sendPacket(remote.ID, remote.addr(), byte(topicNodesPacket), p)
+			p.Nodes = p.Nodes[:0]
+		}
+	}
+}
+
+func (t *udp) sendPacket(toid NodeID, toaddr *net.UDPAddr, ptype byte, req interface{}) (hash []byte, err error) {
+	packet, hash, err := encodePacket(t.priv, ptype, req)
+	if err != nil {
+		return hash, err
+	}
+	glog.V(logger.Detail).Infof(">>> %v to %x@%v\n", nodeEvent(ptype), toid[:8], toaddr)
+	if _, err = t.conn.WriteToUDP(packet, toaddr); err != nil {
+		glog.V(logger.Detail).Infoln("UDP send failed:", err)
+	}
+	return hash, err
+}
+
+// zeroed padding space for encodePacket.
+var headSpace = make([]byte, headSize)
+
+func encodePacket(priv *ecdsa.PrivateKey, ptype byte, req interface{}) (p, hash []byte, err error) {
+	b := new(bytes.Buffer)
+	b.Write(headSpace)
+	b.WriteByte(ptype)
+	if err := rlp.Encode(b, req); err != nil {
+		glog.V(logger.Error).Infoln("error encoding packet:", err)
+		return nil, nil, err
+	}
+	packet := b.Bytes()
+	sig, err := crypto.Sign(crypto.Keccak256(packet[headSize:]), priv)
+	if err != nil {
+		glog.V(logger.Error).Infoln("could not sign packet:", err)
+		return nil, nil, err
+	}
+	copy(packet[macSize:], sig)
+	// add the hash to the front. Note: this doesn't protect the
+	// packet in any way.
+	hash = crypto.Keccak256(packet[macSize:])
+	copy(packet, hash)
+	return packet, hash, nil
+}
+
+// readLoop runs in its own goroutine. it injects ingress UDP packets
+// into the network loop.
+func (t *udp) readLoop() {
+	defer t.conn.Close()
+	// Discovery packets are defined to be no larger than 1280 bytes.
+	// Packets larger than this size will be cut at the end and treated
+	// as invalid because their hash won't match.
+	buf := make([]byte, 1280)
+	for {
+		nbytes, from, err := t.conn.ReadFromUDP(buf)
+		if isTemporaryError(err) {
+			// Ignore temporary read errors.
+			glog.V(logger.Debug).Infof("Temporary read error: %v", err)
+			continue
+		} else if err != nil {
+			// Shut down the loop for permament errors.
+			glog.V(logger.Debug).Infof("Read error: %v", err)
+			return
+		}
+		t.handlePacket(from, buf[:nbytes])
+	}
+}
+
+func isTemporaryError(err error) bool {
+	tempErr, ok := err.(interface {
+		Temporary() bool
+	})
+	return ok && tempErr.Temporary() || isPacketTooBig(err)
+}
+
+func (t *udp) handlePacket(from *net.UDPAddr, buf []byte) error {
+	pkt := ingressPacket{remoteAddr: from}
+	if err := decodePacket(buf, &pkt); err != nil {
+		glog.V(logger.Debug).Infof("Bad packet from %v: %v\n", from, err)
+		return err
+	}
+	t.net.reqReadPacket(pkt)
+	return nil
+}
+
+func decodePacket(buffer []byte, pkt *ingressPacket) error {
+	if len(buffer) < headSize+1 {
+		return errPacketTooSmall
+	}
+	buf := make([]byte, len(buffer))
+	copy(buf, buffer)
+	hash, sig, sigdata := buf[:macSize], buf[macSize:headSize], buf[headSize:]
+	shouldhash := crypto.Keccak256(buf[macSize:])
+	if !bytes.Equal(hash, shouldhash) {
+		return errBadHash
+	}
+	fromID, err := recoverNodeID(crypto.Keccak256(buf[headSize:]), sig)
+	if err != nil {
+		return err
+	}
+	pkt.rawData = buf
+	pkt.hash = hash
+	pkt.remoteID = fromID
+	switch pkt.ev = nodeEvent(sigdata[0]); pkt.ev {
+	case pingPacket:
+		pkt.data = new(ping)
+	case pongPacket:
+		pkt.data = new(pong)
+	case findnodePacket:
+		pkt.data = new(findnode)
+	case neighborsPacket:
+		pkt.data = new(neighbors)
+	case findnodeHashPacket:
+		pkt.data = new(findnodeHash)
+	case topicRegisterPacket:
+		pkt.data = new(topicRegister)
+	case topicQueryPacket:
+		pkt.data = new(topicQuery)
+	case topicNodesPacket:
+		pkt.data = new(topicNodes)
+	default:
+		return fmt.Errorf("unknown packet type: %d", sigdata[0])
+	}
+	s := rlp.NewStream(bytes.NewReader(sigdata[1:]), 0)
+	err = s.Decode(pkt.data)
+	return err
+}
diff --git a/p2p/discv5/udp_notwindows.go b/p2p/discv5/udp_notwindows.go
new file mode 100644
index 000000000..4da18d0f6
--- /dev/null
+++ b/p2p/discv5/udp_notwindows.go
@@ -0,0 +1,26 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+//+build !windows
+
+package discv5
+
+// reports whether err indicates that a UDP packet didn't
+// fit the receive buffer. There is no such error on
+// non-Windows platforms.
+func isPacketTooBig(err error) bool {
+	return false
+}
diff --git a/p2p/discv5/udp_test.go b/p2p/discv5/udp_test.go
new file mode 100644
index 000000000..267eaf225
--- /dev/null
+++ b/p2p/discv5/udp_test.go
@@ -0,0 +1,505 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package discv5
+
+import (
+	"encoding/hex"
+	"errors"
+	"io"
+	"net"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/davecgh/go-spew/spew"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+func init() {
+	spew.Config.DisableMethods = true
+}
+
+// This test checks that isPacketTooBig correctly identifies
+// errors that result from receiving a UDP packet larger
+// than the supplied receive buffer.
+func TestIsPacketTooBig(t *testing.T) {
+	listener, err := net.ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+	sender, err := net.Dial("udp", listener.LocalAddr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer sender.Close()
+
+	sendN := 1800
+	recvN := 300
+	for i := 0; i < 20; i++ {
+		go func() {
+			buf := make([]byte, sendN)
+			for i := range buf {
+				buf[i] = byte(i)
+			}
+			sender.Write(buf)
+		}()
+
+		buf := make([]byte, recvN)
+		listener.SetDeadline(time.Now().Add(1 * time.Second))
+		n, _, err := listener.ReadFrom(buf)
+		if err != nil {
+			if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
+				continue
+			}
+			if !isPacketTooBig(err) {
+				t.Fatal("unexpected read error:", spew.Sdump(err))
+			}
+			continue
+		}
+		if n != recvN {
+			t.Fatalf("short read: %d, want %d", n, recvN)
+		}
+		for i := range buf {
+			if buf[i] != byte(i) {
+				t.Fatalf("error in pattern")
+				break
+			}
+		}
+	}
+}
+
+// shared test variables
+var (
+	futureExp          = uint64(time.Now().Add(10 * time.Hour).Unix())
+	testTarget         = NodeID{0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1}
+	testRemote         = rpcEndpoint{IP: net.ParseIP("1.1.1.1").To4(), UDP: 1, TCP: 2}
+	testLocalAnnounced = rpcEndpoint{IP: net.ParseIP("2.2.2.2").To4(), UDP: 3, TCP: 4}
+	testLocal          = rpcEndpoint{IP: net.ParseIP("3.3.3.3").To4(), UDP: 5, TCP: 6}
+)
+
+// type udpTest struct {
+// 	t                   *testing.T
+// 	pipe                *dgramPipe
+// 	table               *Table
+// 	udp                 *udp
+// 	sent                [][]byte
+// 	localkey, remotekey *ecdsa.PrivateKey
+// 	remoteaddr          *net.UDPAddr
+// }
+//
+// func newUDPTest(t *testing.T) *udpTest {
+// 	test := &udpTest{
+// 		t:          t,
+// 		pipe:       newpipe(),
+// 		localkey:   newkey(),
+// 		remotekey:  newkey(),
+// 		remoteaddr: &net.UDPAddr{IP: net.IP{1, 2, 3, 4}, Port: 30303},
+// 	}
+// 	test.table, test.udp, _ = newUDP(test.localkey, test.pipe, nil, "")
+// 	return test
+// }
+//
+// // handles a packet as if it had been sent to the transport.
+// func (test *udpTest) packetIn(wantError error, ptype byte, data packet) error {
+// 	enc, err := encodePacket(test.remotekey, ptype, data)
+// 	if err != nil {
+// 		return test.errorf("packet (%d) encode error: %v", ptype, err)
+// 	}
+// 	test.sent = append(test.sent, enc)
+// 	if err = test.udp.handlePacket(test.remoteaddr, enc); err != wantError {
+// 		return test.errorf("error mismatch: got %q, want %q", err, wantError)
+// 	}
+// 	return nil
+// }
+//
+// // waits for a packet to be sent by the transport.
+// // validate should have type func(*udpTest, X) error, where X is a packet type.
+// func (test *udpTest) waitPacketOut(validate interface{}) error {
+// 	dgram := test.pipe.waitPacketOut()
+// 	p, _, _, err := decodePacket(dgram)
+// 	if err != nil {
+// 		return test.errorf("sent packet decode error: %v", err)
+// 	}
+// 	fn := reflect.ValueOf(validate)
+// 	exptype := fn.Type().In(0)
+// 	if reflect.TypeOf(p) != exptype {
+// 		return test.errorf("sent packet type mismatch, got: %v, want: %v", reflect.TypeOf(p), exptype)
+// 	}
+// 	fn.Call([]reflect.Value{reflect.ValueOf(p)})
+// 	return nil
+// }
+//
+// func (test *udpTest) errorf(format string, args ...interface{}) error {
+// 	_, file, line, ok := runtime.Caller(2) // errorf + waitPacketOut
+// 	if ok {
+// 		file = filepath.Base(file)
+// 	} else {
+// 		file = "???"
+// 		line = 1
+// 	}
+// 	err := fmt.Errorf(format, args...)
+// 	fmt.Printf("\t%s:%d: %v\n", file, line, err)
+// 	test.t.Fail()
+// 	return err
+// }
+//
+// func TestUDP_packetErrors(t *testing.T) {
+// 	test := newUDPTest(t)
+// 	defer test.table.Close()
+//
+// 	test.packetIn(errExpired, pingPacket, &ping{From: testRemote, To: testLocalAnnounced, Version: Version})
+// 	test.packetIn(errUnsolicitedReply, pongPacket, &pong{ReplyTok: []byte{}, Expiration: futureExp})
+// 	test.packetIn(errUnknownNode, findnodePacket, &findnode{Expiration: futureExp})
+// 	test.packetIn(errUnsolicitedReply, neighborsPacket, &neighbors{Expiration: futureExp})
+// }
+//
+// func TestUDP_findnode(t *testing.T) {
+// 	test := newUDPTest(t)
+// 	defer test.table.Close()
+//
+// 	// put a few nodes into the table. their exact
+// 	// distribution shouldn't matter much, altough we need to
+// 	// take care not to overflow any bucket.
+// 	targetHash := crypto.Keccak256Hash(testTarget[:])
+// 	nodes := &nodesByDistance{target: targetHash}
+// 	for i := 0; i < bucketSize; i++ {
+// 		nodes.push(nodeAtDistance(test.table.self.sha, i+2), bucketSize)
+// 	}
+// 	test.table.stuff(nodes.entries)
+//
+// 	// ensure there's a bond with the test node,
+// 	// findnode won't be accepted otherwise.
+// 	test.table.db.updateNode(NewNode(
+// 		PubkeyID(&test.remotekey.PublicKey),
+// 		test.remoteaddr.IP,
+// 		uint16(test.remoteaddr.Port),
+// 		99,
+// 	))
+// 	// check that closest neighbors are returned.
+// 	test.packetIn(nil, findnodePacket, &findnode{Target: testTarget, Expiration: futureExp})
+// 	expected := test.table.closest(targetHash, bucketSize)
+//
+// 	waitNeighbors := func(want []*Node) {
+// 		test.waitPacketOut(func(p *neighbors) {
+// 			if len(p.Nodes) != len(want) {
+// 				t.Errorf("wrong number of results: got %d, want %d", len(p.Nodes), bucketSize)
+// 			}
+// 			for i := range p.Nodes {
+// 				if p.Nodes[i].ID != want[i].ID {
+// 					t.Errorf("result mismatch at %d:\n  got:  %v\n  want: %v", i, p.Nodes[i], expected.entries[i])
+// 				}
+// 			}
+// 		})
+// 	}
+// 	waitNeighbors(expected.entries[:maxNeighbors])
+// 	waitNeighbors(expected.entries[maxNeighbors:])
+// }
+//
+// func TestUDP_findnodeMultiReply(t *testing.T) {
+// 	test := newUDPTest(t)
+// 	defer test.table.Close()
+//
+// 	// queue a pending findnode request
+// 	resultc, errc := make(chan []*Node), make(chan error)
+// 	go func() {
+// 		rid := PubkeyID(&test.remotekey.PublicKey)
+// 		ns, err := test.udp.findnode(rid, test.remoteaddr, testTarget)
+// 		if err != nil && len(ns) == 0 {
+// 			errc <- err
+// 		} else {
+// 			resultc <- ns
+// 		}
+// 	}()
+//
+// 	// wait for the findnode to be sent.
+// 	// after it is sent, the transport is waiting for a reply
+// 	test.waitPacketOut(func(p *findnode) {
+// 		if p.Target != testTarget {
+// 			t.Errorf("wrong target: got %v, want %v", p.Target, testTarget)
+// 		}
+// 	})
+//
+// 	// send the reply as two packets.
+// 	list := []*Node{
+// 		MustParseNode("enode://ba85011c70bcc5c04d8607d3a0ed29aa6179c092cbdda10d5d32684fb33ed01bd94f588ca8f91ac48318087dcb02eaf36773a7a453f0eedd6742af668097b29c@10.0.1.16:30303?discport=30304"),
+// 		MustParseNode("enode://81fa361d25f157cd421c60dcc28d8dac5ef6a89476633339c5df30287474520caca09627da18543d9079b5b288698b542d56167aa5c09111e55acdbbdf2ef799@10.0.1.16:30303"),
+// 		MustParseNode("enode://9bffefd833d53fac8e652415f4973bee289e8b1a5c6c4cbe70abf817ce8a64cee11b823b66a987f51aaa9fba0d6a91b3e6bf0d5a5d1042de8e9eeea057b217f8@10.0.1.36:30301?discport=17"),
+// 		MustParseNode("enode://1b5b4aa662d7cb44a7221bfba67302590b643028197a7d5214790f3bac7aaa4a3241be9e83c09cf1f6c69d007c634faae3dc1b1221793e8446c0b3a09de65960@10.0.1.16:30303"),
+// 	}
+// 	rpclist := make([]rpcNode, len(list))
+// 	for i := range list {
+// 		rpclist[i] = nodeToRPC(list[i])
+// 	}
+// 	test.packetIn(nil, neighborsPacket, &neighbors{Expiration: futureExp, Nodes: rpclist[:2]})
+// 	test.packetIn(nil, neighborsPacket, &neighbors{Expiration: futureExp, Nodes: rpclist[2:]})
+//
+// 	// check that the sent neighbors are all returned by findnode
+// 	select {
+// 	case result := <-resultc:
+// 		if !reflect.DeepEqual(result, list) {
+// 			t.Errorf("neighbors mismatch:\n  got:  %v\n  want: %v", result, list)
+// 		}
+// 	case err := <-errc:
+// 		t.Errorf("findnode error: %v", err)
+// 	case <-time.After(5 * time.Second):
+// 		t.Error("findnode did not return within 5 seconds")
+// 	}
+// }
+//
+// func TestUDP_successfulPing(t *testing.T) {
+// 	test := newUDPTest(t)
+// 	added := make(chan *Node, 1)
+// 	test.table.nodeAddedHook = func(n *Node) { added <- n }
+// 	defer test.table.Close()
+//
+// 	// The remote side sends a ping packet to initiate the exchange.
+// 	go test.packetIn(nil, pingPacket, &ping{From: testRemote, To: testLocalAnnounced, Version: Version, Expiration: futureExp})
+//
+// 	// the ping is replied to.
+// 	test.waitPacketOut(func(p *pong) {
+// 		pinghash := test.sent[0][:macSize]
+// 		if !bytes.Equal(p.ReplyTok, pinghash) {
+// 			t.Errorf("got pong.ReplyTok %x, want %x", p.ReplyTok, pinghash)
+// 		}
+// 		wantTo := rpcEndpoint{
+// 			// The mirrored UDP address is the UDP packet sender
+// 			IP: test.remoteaddr.IP, UDP: uint16(test.remoteaddr.Port),
+// 			// The mirrored TCP port is the one from the ping packet
+// 			TCP: testRemote.TCP,
+// 		}
+// 		if !reflect.DeepEqual(p.To, wantTo) {
+// 			t.Errorf("got pong.To %v, want %v", p.To, wantTo)
+// 		}
+// 	})
+//
+// 	// remote is unknown, the table pings back.
+// 	test.waitPacketOut(func(p *ping) error {
+// 		if !reflect.DeepEqual(p.From, test.udp.ourEndpoint) {
+// 			t.Errorf("got ping.From %v, want %v", p.From, test.udp.ourEndpoint)
+// 		}
+// 		wantTo := rpcEndpoint{
+// 			// The mirrored UDP address is the UDP packet sender.
+// 			IP: test.remoteaddr.IP, UDP: uint16(test.remoteaddr.Port),
+// 			TCP: 0,
+// 		}
+// 		if !reflect.DeepEqual(p.To, wantTo) {
+// 			t.Errorf("got ping.To %v, want %v", p.To, wantTo)
+// 		}
+// 		return nil
+// 	})
+// 	test.packetIn(nil, pongPacket, &pong{Expiration: futureExp})
+//
+// 	// the node should be added to the table shortly after getting the
+// 	// pong packet.
+// 	select {
+// 	case n := <-added:
+// 		rid := PubkeyID(&test.remotekey.PublicKey)
+// 		if n.ID != rid {
+// 			t.Errorf("node has wrong ID: got %v, want %v", n.ID, rid)
+// 		}
+// 		if !bytes.Equal(n.IP, test.remoteaddr.IP) {
+// 			t.Errorf("node has wrong IP: got %v, want: %v", n.IP, test.remoteaddr.IP)
+// 		}
+// 		if int(n.UDP) != test.remoteaddr.Port {
+// 			t.Errorf("node has wrong UDP port: got %v, want: %v", n.UDP, test.remoteaddr.Port)
+// 		}
+// 		if n.TCP != testRemote.TCP {
+// 			t.Errorf("node has wrong TCP port: got %v, want: %v", n.TCP, testRemote.TCP)
+// 		}
+// 	case <-time.After(2 * time.Second):
+// 		t.Errorf("node was not added within 2 seconds")
+// 	}
+// }
+
+var testPackets = []struct {
+	input      string
+	wantPacket interface{}
+}{
+	{
+		input: "71dbda3a79554728d4f94411e42ee1f8b0d561c10e1e5f5893367948c6a7d70bb87b235fa28a77070271b6c164a2dce8c7e13a5739b53b5e96f2e5acb0e458a02902f5965d55ecbeb2ebb6cabb8b2b232896a36b737666c55265ad0a68412f250001ea04cb847f000001820cfa8215a8d790000000000000000000000000000000018208ae820d058443b9a355",
+		wantPacket: &ping{
+			Version:    4,
+			From:       rpcEndpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
+			To:         rpcEndpoint{net.ParseIP("::1"), 2222, 3333},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{},
+		},
+	},
+	{
+		input: "e9614ccfd9fc3e74360018522d30e1419a143407ffcce748de3e22116b7e8dc92ff74788c0b6663aaa3d67d641936511c8f8d6ad8698b820a7cf9e1be7155e9a241f556658c55428ec0563514365799a4be2be5a685a80971ddcfa80cb422cdd0101ec04cb847f000001820cfa8215a8d790000000000000000000000000000000018208ae820d058443b9a3550102",
+		wantPacket: &ping{
+			Version:    4,
+			From:       rpcEndpoint{net.ParseIP("127.0.0.1").To4(), 3322, 5544},
+			To:         rpcEndpoint{net.ParseIP("::1"), 2222, 3333},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0x01}, {0x02}},
+		},
+	},
+	{
+		input: "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",
+		wantPacket: &ping{
+			Version:    555,
+			From:       rpcEndpoint{net.ParseIP("2001:db8:3c4d:15::abcd:ef12"), 3322, 5544},
+			To:         rpcEndpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0xC5, 0x01, 0x02, 0x03, 0x04, 0x05}},
+		},
+	},
+	{
+		input: "09b2428d83348d27cdf7064ad9024f526cebc19e4958f0fdad87c15eb598dd61d08423e0bf66b2069869e1724125f820d851c136684082774f870e614d95a2855d000f05d1648b2d5945470bc187c2d2216fbe870f43ed0909009882e176a46b0102f846d79020010db885a308d313198a2e037073488208ae82823aa0fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c9548443b9a355c6010203c2040506a0c969a58f6f9095004c0177a6b47f451530cab38966a25cca5cb58f055542124e",
+		wantPacket: &pong{
+			To:         rpcEndpoint{net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"), 2222, 33338},
+			ReplyTok:   common.Hex2Bytes("fbc914b16819237dcd8801d7e53f69e9719adecb3cc0e790c57e91ca4461c954"),
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0xC6, 0x01, 0x02, 0x03, 0xC2, 0x04, 0x05}, {0x06}},
+		},
+	},
+	{
+		input: "c7c44041b9f7c7e41934417ebac9a8e1a4c6298f74553f2fcfdcae6ed6fe53163eb3d2b52e39fe91831b8a927bf4fc222c3902202027e5e9eb812195f95d20061ef5cd31d502e47ecb61183f74a504fe04c51e73df81f25c4d506b26db4517490103f84eb840ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be00812904767bf5ccd1fc7f8443b9a35582999983999999280dc62cc8255c73471e0a61da0c89acdc0e035e260add7fc0c04ad9ebf3919644c91cb247affc82b69bd2ca235c71eab8e49737c937a2c396",
+		wantPacket: &findnode{
+			Target:     MustHexID("ca634cae0d49acb401d8a4c6b6fe8c55b70d115bf400769cc1400f3258cd31387574077f301b421bc84df7266c44e9e6d569fc56be00812904767bf5ccd1fc7f"),
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0x82, 0x99, 0x99}, {0x83, 0x99, 0x99, 0x99}},
+		},
+	},
+	{
+		input: "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",
+		wantPacket: &neighbors{
+			Nodes: []rpcNode{
+				{
+					ID:  MustHexID("3155e1427f85f10a5c9a7755877748041af1bcd8d474ec065eb33df57a97babf54bfd2103575fa829115d224c523596b401065a97f74010610fce76382c0bf32"),
+					IP:  net.ParseIP("99.33.22.55").To4(),
+					UDP: 4444,
+					TCP: 4445,
+				},
+				{
+					ID:  MustHexID("312c55512422cf9b8a4097e9a6ad79402e87a15ae909a4bfefa22398f03d20951933beea1e4dfa6f968212385e829f04c2d314fc2d4e255e0d3bc08792b069db"),
+					IP:  net.ParseIP("1.2.3.4").To4(),
+					UDP: 1,
+					TCP: 1,
+				},
+				{
+					ID:  MustHexID("38643200b172dcfef857492156971f0e6aa2c538d8b74010f8e140811d53b98c765dd2d96126051913f44582e8c199ad7c6d6819e9a56483f637feaac9448aac"),
+					IP:  net.ParseIP("2001:db8:3c4d:15::abcd:ef12"),
+					UDP: 3333,
+					TCP: 3333,
+				},
+				{
+					ID:  MustHexID("8dcab8618c3253b558d459da53bd8fa68935a719aff8b811197101a4b2b47dd2d47295286fc00cc081bb542d760717d1bdd6bec2c37cd72eca367d6dd3b9df73"),
+					IP:  net.ParseIP("2001:db8:85a3:8d3:1319:8a2e:370:7348"),
+					UDP: 999,
+					TCP: 1000,
+				},
+			},
+			Expiration: 1136239445,
+			Rest:       []rlp.RawValue{{0x01}, {0x02}, {0x03}},
+		},
+	},
+}
+
+func TestForwardCompatibility(t *testing.T) {
+	t.Skip("skipped while working on discovery v5")
+
+	testkey, _ := crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+	wantNodeID := PubkeyID(&testkey.PublicKey)
+
+	for _, test := range testPackets {
+		input, err := hex.DecodeString(test.input)
+		if err != nil {
+			t.Fatalf("invalid hex: %s", test.input)
+		}
+		var pkt ingressPacket
+		if err := decodePacket(input, &pkt); err != nil {
+			t.Errorf("did not accept packet %s\n%v", test.input, err)
+			continue
+		}
+		if !reflect.DeepEqual(pkt.data, test.wantPacket) {
+			t.Errorf("got %s\nwant %s", spew.Sdump(pkt.data), spew.Sdump(test.wantPacket))
+		}
+		if pkt.remoteID != wantNodeID {
+			t.Errorf("got id %v\nwant id %v", pkt.remoteID, wantNodeID)
+		}
+	}
+}
+
+// dgramPipe is a fake UDP socket. It queues all sent datagrams.
+type dgramPipe struct {
+	mu      *sync.Mutex
+	cond    *sync.Cond
+	closing chan struct{}
+	closed  bool
+	queue   [][]byte
+}
+
+func newpipe() *dgramPipe {
+	mu := new(sync.Mutex)
+	return &dgramPipe{
+		closing: make(chan struct{}),
+		cond:    &sync.Cond{L: mu},
+		mu:      mu,
+	}
+}
+
+// WriteToUDP queues a datagram.
+func (c *dgramPipe) WriteToUDP(b []byte, to *net.UDPAddr) (n int, err error) {
+	msg := make([]byte, len(b))
+	copy(msg, b)
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.closed {
+		return 0, errors.New("closed")
+	}
+	c.queue = append(c.queue, msg)
+	c.cond.Signal()
+	return len(b), nil
+}
+
+// ReadFromUDP just hangs until the pipe is closed.
+func (c *dgramPipe) ReadFromUDP(b []byte) (n int, addr *net.UDPAddr, err error) {
+	<-c.closing
+	return 0, nil, io.EOF
+}
+
+func (c *dgramPipe) Close() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if !c.closed {
+		close(c.closing)
+		c.closed = true
+	}
+	return nil
+}
+
+func (c *dgramPipe) LocalAddr() net.Addr {
+	return &net.UDPAddr{IP: testLocal.IP, Port: int(testLocal.UDP)}
+}
+
+func (c *dgramPipe) waitPacketOut() []byte {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for len(c.queue) == 0 {
+		c.cond.Wait()
+	}
+	p := c.queue[0]
+	copy(c.queue, c.queue[1:])
+	c.queue = c.queue[:len(c.queue)-1]
+	return p
+}
diff --git a/p2p/discv5/udp_windows.go b/p2p/discv5/udp_windows.go
new file mode 100644
index 000000000..1ab9d655e
--- /dev/null
+++ b/p2p/discv5/udp_windows.go
@@ -0,0 +1,40 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+//+build windows
+
+package discv5
+
+import (
+	"net"
+	"os"
+	"syscall"
+)
+
+const _WSAEMSGSIZE = syscall.Errno(10040)
+
+// reports whether err indicates that a UDP packet didn't
+// fit the receive buffer. On Windows, WSARecvFrom returns
+// code WSAEMSGSIZE and no data if this happens.
+func isPacketTooBig(err error) bool {
+	if opErr, ok := err.(*net.OpError); ok {
+		if scErr, ok := opErr.Err.(*os.SyscallError); ok {
+			return scErr.Err == _WSAEMSGSIZE
+		}
+		return opErr.Err == _WSAEMSGSIZE
+	}
+	return false
+}
diff --git a/p2p/server.go b/p2p/server.go
index 8e3cd93f9..649fbfb82 100644
--- a/p2p/server.go
+++ b/p2p/server.go
@@ -28,6 +28,7 @@ import (
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
 	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/p2p/discv5"
 	"github.com/ethereum/go-ethereum/p2p/nat"
 )
 
@@ -72,6 +73,8 @@ type Config struct {
 	// or not. Disabling is usually useful for protocol debugging (manual topology).
 	Discovery bool
 
+	DiscoveryV5 bool
+
 	// Name sets the node name of this server.
 	// Use common.MakeName to create a name that follows existing conventions.
 	Name string
@@ -105,6 +108,8 @@ type Config struct {
 	// the server is started.
 	ListenAddr string
 
+	ListenAddrV5 string
+
 	// If set to a non-nil value, the given NAT port mapper
 	// is used to make the listening port available to the
 	// Internet.
@@ -135,6 +140,7 @@ type Server struct {
 	listener     net.Listener
 	ourHandshake *protoHandshake
 	lastLookup   time.Time
+	DiscV5       *discv5.Network
 
 	// These are for Peers, PeerCount (and nothing else).
 	peerOp     chan peerOpFunc
@@ -352,6 +358,17 @@ func (srv *Server) Start() (err error) {
 		srv.ntab = ntab
 	}
 
+	if srv.DiscoveryV5 {
+		ntab, err := discv5.ListenUDP(srv.PrivateKey, srv.ListenAddrV5, srv.NAT, "") //srv.NodeDatabase)
+		if err != nil {
+			return err
+		}
+		if err := ntab.SetFallbackNodes(discv5.BootNodes); err != nil {
+			return err
+		}
+		srv.DiscV5 = ntab
+	}
+
 	dynPeers := (srv.MaxPeers + 1) / 2
 	if !srv.Discovery {
 		dynPeers = 0
@@ -527,6 +544,9 @@ running:
 	if srv.ntab != nil {
 		srv.ntab.Close()
 	}
+	if srv.DiscV5 != nil {
+		srv.DiscV5.Close()
+	}
 	// Disconnect all peers.
 	for _, p := range peers {
 		p.Disconnect(DiscQuitting)