path: root/simulation/network-model.go

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
}