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don't perform a decrease during single packet loss events

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This commit is contained in:
Stephen Birarda 2016-03-18 14:03:56 -07:00
parent 13a906aa20
commit 93a00c3d5d
2 changed files with 14 additions and 6 deletions
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19
libraries/networking/src/udt/CongestionControl.cpp
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@ -138,18 +138,23 @@ void DefaultCC::onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {
}
}
_loss = true;
static const double INTER_PACKET_ARRIVAL_INCREASE = 1.125;
static const int MAX_DECREASES_PER_CONGESTION_EPOCH = 5;
// check if this NAK starts a new congestion period - this will be the case if the
// NAK received occured for a packet sent after the last decrease
if (rangeStart > _lastDecreaseMaxSeq) {
// check if we should skip handling of this loss event
// we do this if this congestion event represents only a single packet loss
if (rangeStart == rangeEnd) {
return;
}
_lastDecreasePeriod = _packetSendPeriod;
_packetSendPeriod = ceil(_packetSendPeriod * INTER_PACKET_ARRIVAL_INCREASE);
// use EWMA to update the average number of NAKs per congestion
static const double NAK_EWMA_ALPHA = 0.125;
_avgNAKNum = (int)ceil(_avgNAKNum * (1 - NAK_EWMA_ALPHA) + _nakCount * NAK_EWMA_ALPHA);
@ -159,7 +164,7 @@ void DefaultCC::onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {
_decreaseCount = 1;
_lastDecreaseMaxSeq = _sendCurrSeqNum;
if (_avgNAKNum < 1) {
_randomDecreaseThreshold = 1;
} else {
@ -177,6 +182,8 @@ void DefaultCC::onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {
_packetSendPeriod = ceil(_packetSendPeriod * INTER_PACKET_ARRIVAL_INCREASE);
_lastDecreaseMaxSeq = _sendCurrSeqNum;
}
_loss = true;
}
// Note: This isn't currently being called by anything since we, unlike UDT, don't have TTL on our packets

1
libraries/networking/src/udt/CongestionControl.h
View file

@ -118,6 +118,7 @@ private:
SequenceNumber _slowStartLastACK; // last ACKed seq num from previous slow start check
bool _loss { false }; // if loss happened since last rate increase
SequenceNumber _lastDecreaseMaxSeq; // max pkt seq num sent out when last decrease happened
SequenceNumber _firstLossFromEvent; // sequence number of first packet ignored for last congestion event
double _lastDecreasePeriod { 1 }; // value of _packetSendPeriod when last decrease happened
int _nakCount { 0 }; // number of NAKs in congestion epoch
int _randomDecreaseThreshold { 1 }; // random threshold on decrease by number of loss events