1 files changed, 68 insertions, 0 deletions
diff --git a/simulation/network-model.go b/simulation/network-model.go
new file mode 100644
index 0000000..041bd12
--- /dev/null
+++ b/simulation/network-model.go
@@ -0,0 +1,68 @@
+package simulation
+
+import (
+	"math/rand"
+	"time"
+)
+
+// Model is the interface for define a given network environment.
+type Model interface {
+	// LossRate returns the message lost ratio between [0, 1)
+	LossRate() float64
+
+	// Delay returns the send delay of the message.  This function is called each
+	// time before the message is sent, so one can return different number each
+	// time.
+	Delay() time.Duration
+}
+
+// LosslessNetwork is a lossless network model.
+type LosslessNetwork struct {
+}
+
+// LossRate returns lossrate for the model.
+func (l *LosslessNetwork) LossRate() float64 {
+	return 0.0
+}
+
+// Delay returns the send delay of a given message.
+func (l *LosslessNetwork) Delay() time.Duration {
+	return time.Duration(0)
+}
+
+// FixedLostNoDelayModel is a network with no delay and a fixed lost
+// ratio.
+type FixedLostNoDelayModel struct {
+	LossRateValue float64
+}
+
+// LossRate returns lossrate for the model.
+func (f *FixedLostNoDelayModel) LossRate() float64 {
+	return f.LossRateValue
+}
+
+// Delay returns the send delay of a given message.
+func (f *FixedLostNoDelayModel) Delay() time.Duration {
+	return time.Duration(0)
+}
+
+// NormalNetwork is a model where it's delay is a normal distribution.
+type NormalNetwork struct {
+	Sigma         float64
+	Mean          float64
+	LossRateValue float64
+}
+
+// LossRate returns lossrate for the model.
+func (n *NormalNetwork) LossRate() float64 {
+	return n.LossRateValue
+}
+
+// Delay returns the send delay of a given message.
+func (n *NormalNetwork) Delay() time.Duration {
+	delay := rand.NormFloat64()*n.Sigma + n.Mean
+	if delay < 0 {
+		delay = n.Sigma / 2
+	}
+	return time.Duration(delay) * time.Millisecond
+}