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remove the N connection simulation from the Reno code

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This commit is contained in:
Marten Seemann 2020-07-22 13:56:08 +07:00
parent df2998de4f
commit 6328acffd7
2 changed files with 8 additions and 90 deletions
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36
internal/congestion/cubic_sender.go
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@ -10,12 +10,12 @@ import (
const (
// maxDatagramSize is the default maximum packet size used in the Linux TCP implementation.
// Used in QUIC for congestion window computations in bytes.
maxDatagramSize = protocol.ByteCount(protocol.MaxPacketSizeIPv4)
maxBurstBytes = 3 * maxDatagramSize
renoBeta float32 = 0.7 // Reno backoff factor.
maxCongestionWindow = protocol.MaxCongestionWindowPackets * maxDatagramSize
minCongestionWindow = 2 * maxDatagramSize
initialCongestionWindow = 32 * maxDatagramSize
maxDatagramSize = protocol.ByteCount(protocol.MaxPacketSizeIPv4)
maxBurstBytes = 3 * maxDatagramSize
renoBeta = 0.7 // Reno backoff factor.
maxCongestionWindow = protocol.MaxCongestionWindowPackets * maxDatagramSize
minCongestionWindow = 2 * maxDatagramSize
initialCongestionWindow = 32 * maxDatagramSize
)
type cubicSender struct {
@ -52,9 +52,6 @@ type cubicSender struct {
// Slow start congestion window in bytes, aka ssthresh.
slowStartThreshold protocol.ByteCount
// Number of connections to simulate.
numConnections int
// ACK counter for the Reno implementation.
numAckedPackets uint64
@ -82,7 +79,6 @@ func newCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestio
minCongestionWindow: minCongestionWindow,
slowStartThreshold: initialMaxCongestionWindow,
maxCongestionWindow: initialMaxCongestionWindow,
numConnections: defaultNumConnections,
cubic: NewCubic(clock),
clock: clock,
reno: reno,
@ -167,7 +163,7 @@ func (c *cubicSender) OnPacketLost(
c.lastCutbackExitedSlowstart = c.InSlowStart()
if c.reno {
c.congestionWindow = protocol.ByteCount(float32(c.congestionWindow) * c.renoBeta())
c.congestionWindow = protocol.ByteCount(float64(c.congestionWindow) * renoBeta)
} else {
c.congestionWindow = c.cubic.CongestionWindowAfterPacketLoss(c.congestionWindow)
}
@ -181,14 +177,6 @@ func (c *cubicSender) OnPacketLost(
c.numAckedPackets = 0
}
func (c *cubicSender) renoBeta() float32 {
// kNConnectionBeta is the backoff factor after loss for our N-connection
// emulation, which emulates the effective backoff of an ensemble of N
// TCP-Reno connections on a single loss event. The effective multiplier is
// computed as:
return (float32(c.numConnections) - 1. + renoBeta) / float32(c.numConnections)
}
// Called when we receive an ack. Normal TCP tracks how many packets one ack
// represents, but quic has a separate ack for each packet.
func (c *cubicSender) maybeIncreaseCwnd(
@ -215,9 +203,7 @@ func (c *cubicSender) maybeIncreaseCwnd(
if c.reno {
// Classic Reno congestion avoidance.
c.numAckedPackets++
// Divide by num_connections to smoothly increase the CWND at a faster
// rate than conventional Reno.
if c.numAckedPackets*uint64(c.numConnections) >= uint64(c.congestionWindow)/uint64(maxDatagramSize) {
if c.numAckedPackets >= uint64(c.congestionWindow/maxDatagramSize) {
c.congestionWindow += maxDatagramSize
c.numAckedPackets = 0
}
@ -246,12 +232,6 @@ func (c *cubicSender) BandwidthEstimate() Bandwidth {
return BandwidthFromDelta(c.GetCongestionWindow(), srtt)
}
// SetNumEmulatedConnections sets the number of emulated connections
func (c *cubicSender) SetNumEmulatedConnections(n int) {
c.numConnections = utils.Max(n, 1)
c.cubic.SetNumConnections(c.numConnections)
}
// OnRetransmissionTimeout is called on an retransmission timeout
func (c *cubicSender) OnRetransmissionTimeout(packetsRetransmitted bool) {
c.largestSentAtLastCutback = protocol.InvalidPacketNumber