create the base of the TCPVegasCC class

libraries/networking/src/udt/CongestionControl.cpp

@@ -45,7 +45,7 @@ DefaultCC::DefaultCC() :
 {
     _mss = udt::MAX_PACKET_SIZE_WITH_UDP_HEADER;
     
-    _congestionWindowSize = 16.0;
+    _congestionWindowSize = 16;
     setPacketSendPeriod(1.0);
 }
 
@@ -218,7 +218,7 @@ void DefaultCC::stopSlowStart() {
         // If no receiving rate is observed, we have to compute the sending
         // rate according to the current window size, and decrease it
         // using the method below.
-        setPacketSendPeriod(_congestionWindowSize / (_rtt + synInterval()));
+        setPacketSendPeriod(double(_congestionWindowSize) / (_rtt + synInterval()));
     }
 }
 

libraries/networking/src/udt/CongestionControl.h

@@ -43,6 +43,7 @@ public:
     virtual void onACK(SequenceNumber ackNum) {}
     virtual void onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) {}
     virtual void onTimeout() {}
+    virtual void onPacketSent(int packetSize, SequenceNumber seqNum) {}
 protected:
     void setAckInterval(int ackInterval) { _ackInterval = ackInterval; }
     void setRTO(int rto) { _userDefinedRTO = true; _rto = rto; }
@@ -57,11 +58,11 @@ protected:
     void setPacketSendPeriod(double newSendPeriod); // call this internally to ensure send period doesn't go past max bandwidth
     
     double _packetSendPeriod { 1.0 }; // Packet sending period, in microseconds
-    double _congestionWindowSize { 16.0 }; // Congestion window size, in packets
+    uint64_t _congestionWindowSize { 16 }; // Congestion window size, in packets
     
     int _bandwidth { 0 }; // estimated bandwidth, packets per second
     std::atomic<int> _maxBandwidth { -1 }; // Maximum desired bandwidth, bits per second
-    double _maxCongestionWindowSize { 0.0 }; // maximum cwnd size, in packets
+    uint64_t _maxCongestionWindowSize { 0 }; // maximum cwnd size, in packets
     
     int _mss { 0 }; // Maximum Packet Size, including all packet headers
     SequenceNumber _sendCurrSeqNum; // current maximum seq num sent out

libraries/networking/src/udt/Connection.cpp

@@ -112,13 +112,13 @@ SendQueue& Connection::getSendQueue() {
         qCDebug(networking) << "Created SendQueue for connection to" << _destination;
 #endif
 
-        QObject::connect(_sendQueue.get(), &SendQueue::packetSent, this, &Connection::packetSent);
         QObject::connect(_sendQueue.get(), &SendQueue::packetSent, this, &Connection::recordSentPackets);
         QObject::connect(_sendQueue.get(), &SendQueue::packetRetransmitted, this, &Connection::recordRetransmission);
         QObject::connect(_sendQueue.get(), &SendQueue::queueInactive, this, &Connection::queueInactive);
         QObject::connect(_sendQueue.get(), &SendQueue::timeout, this, &Connection::queueTimeout);
         QObject::connect(_sendQueue.get(), &SendQueue::shortCircuitLoss, this, &Connection::queueShortCircuitLoss);
 
+        
         // set defaults on the send queue from our congestion control object and estimatedTimeout()
         _sendQueue->setPacketSendPeriod(_congestionControl->_packetSendPeriod);
         _sendQueue->setSyncInterval(_synInterval);
@@ -260,12 +260,16 @@ void Connection::sync() {
     }
 }
 
-void Connection::recordSentPackets(int dataSize, int payloadSize) {
+void Connection::recordSentPackets(int dataSize, int payloadSize, SequenceNumber seqNum) {
     _stats.recordSentPackets(payloadSize, dataSize);
+
+    _congestionControl->onPacketSent(dataSize, seqNum);
 }
 
-void Connection::recordRetransmission() {
+void Connection::recordRetransmission(int packetSize, SequenceNumber seqNum) {
     _stats.record(ConnectionStats::Stats::Retransmission);
+
+    _congestionControl->onPacketSent(packetSize, seqNum);
 }
 
 void Connection::sendACK(bool wasCausedBySyncTimeout) {

libraries/networking/src/udt/Connection.h

@@ -87,8 +87,8 @@ signals:
     void receiverHandshakeRequestComplete(const HifiSockAddr& sockAddr);
 
 private slots:
-    void recordSentPackets(int payload, int total);
+    void recordSentPackets(int dataSize, int payloadSize, SequenceNumber seqNum);
-    void recordRetransmission();
+    void recordRetransmission(int packetSize, SequenceNumber sequenceNumber);
     void queueInactive();
     void queueTimeout();
     void queueShortCircuitLoss(quint32 sequenceNumber);

libraries/networking/src/udt/Constants.h

@@ -17,6 +17,7 @@
 #include "SequenceNumber.h"
 
 namespace udt {
+
     static const int UDP_IPV4_HEADER_SIZE = 28;
     static const int MAX_PACKET_SIZE_WITH_UDP_HEADER = 1492;
     static const int MAX_PACKET_SIZE = MAX_PACKET_SIZE_WITH_UDP_HEADER - UDP_IPV4_HEADER_SIZE;

libraries/networking/src/udt/SendQueue.cpp

@@ -242,7 +242,7 @@ bool SendQueue::sendNewPacketAndAddToSentList(std::unique_ptr<Packet> newPacket,
     newPacket->writeSequenceNumber(sequenceNumber);
 
     // Save packet/payload size before we move it
-    auto packetSize = newPacket->getDataSize();
+    auto packetSize = newPacket->getWireSize();
     auto payloadSize = newPacket->getPayloadSize();
     
     auto bytesWritten = sendPacket(*newPacket);
@@ -256,7 +256,7 @@ bool SendQueue::sendNewPacketAndAddToSentList(std::unique_ptr<Packet> newPacket,
     }
     Q_ASSERT_X(!newPacket, "SendQueue::sendNewPacketAndAddToSentList()", "Overriden packet in sent list");
     
-    emit packetSent(packetSize, payloadSize);
+    emit packetSent(packetSize, payloadSize, sequenceNumber);
 
     if (bytesWritten < 0) {
         // this is a short-circuit loss - we failed to put this packet on the wire
@@ -492,7 +492,7 @@ bool SendQueue::maybeResendPacket() {
                     sentLocker.unlock();
                 }
                 
-                emit packetRetransmitted();
+                emit packetRetransmitted(resendPacket.getWireSize(), it->first);
                 
                 // Signal that we did resend a packet
                 return true;

libraries/networking/src/udt/SendQueue.h

@@ -74,8 +74,8 @@ public slots:
     void handshakeACK(SequenceNumber initialSequenceNumber);
 
 signals:
-    void packetSent(int dataSize, int payloadSize);
+    void packetSent(int dataSize, int payloadSize, SequenceNumber seqNum);
-    void packetRetransmitted();
+    void packetRetransmitted(int dataSize, SequenceNumber seqNum);
     
     void queueInactive();
 

libraries/networking/src/udt/Socket.h

@@ -22,7 +22,7 @@
 #include <QtNetwork/QUdpSocket>
 
 #include "../HifiSockAddr.h"
-#include "CongestionControl.h"
+#include "TCPVegasCC.h"
 #include "Connection.h"
 #include "TCPRenoCC.h"
 
@@ -132,7 +132,7 @@ private:
 
     int _maxBandwidth { -1 };
 
-    std::unique_ptr<CongestionControlVirtualFactory> _ccFactory { new CongestionControlFactory<TCPRenoCC>() };
+    std::unique_ptr<CongestionControlVirtualFactory> _ccFactory { new CongestionControlFactory<TCPVegasCC>() };
     
     friend UDTTest;
 };

libraries/networking/src/udt/TCPVegasCC.cpp

@@ -0,0 +1,123 @@
+//
+//  TCPVegasCC.cpp
+//  libraries/networking/src/udt
+//
+//  Created by Stephen Birarda on 2016-09-20.
+//  Copyright 2016 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include "TCPVegasCC.h"
+
+#include <QtCore/QtGlobal>
+
+using namespace udt;
+using namespace std::chrono;
+
+void TCPVegasCC::onACK(SequenceNumber ackNum) {
+    auto it = _sentPacketTimes.find(ackNum);
+
+    if (it != _sentPacketTimes.end()) {
+
+        // calculate the RTT (time now - time ACK sent)
+        auto now = p_high_resolution_clock::now();
+        int lastRTT = duration_cast<microseconds>(now - it->second.first).count();
+
+        if (lastRTT < 0) {
+            Q_ASSERT_X(false, "TCPVegasCC::onACK", "calculated an RTT that is not > 0");
+            return;
+        } else if (lastRTT == 0) {
+            // we do not allow a 0 microsecond RTT
+            lastRTT = 1;
+        }
+
+        // keep track of the lowest RTT during connection
+        _baseRTT = std::min(_baseRTT, lastRTT);
+
+        // find the min RTT during the last RTT
+        _currentMinRTT = std::min(_currentMinRTT, lastRTT);
+
+        ++_numRTT;
+
+        if (ackNum > _lastRTTMaxSeqNum) {
+            performCongestionAvoidance(ackNum);
+        }
+
+    } else {
+        Q_ASSERT_X(false,
+                   "TCPVegasCC::onACK",
+                   "called with a sequence number that has not been sent");
+    }
+}
+
+void TCPVegasCC::performCongestionAvoidance(udt::SequenceNumber ack) {
+    static int VEGAS_MIN_RTT_FOR_CALC = 3;
+
+    static uint64_t VEGAS_ALPHA_SEGMENTS = 2;
+    static uint64_t VEGAS_BETA_SEGMENTS = 4;
+    static uint64_t VEGAS_GAMMA_SEGMENTS = 1;
+
+    if (_numRTT < VEGAS_MIN_RTT_FOR_CALC) {
+        // Vegas calculations are only done if there are enough RTT samples to be
+        // pretty sure that at least one sample did not come from a delayed ACK.
+        // If that is the case, we fallback to the Reno behaviour
+        TCPRenoCC::performCongestionAvoidance(ack);
+    } else {
+        // There are enough RTT samples, use the Vegas algorithm to see if we should
+        // increase or decrease the congestion window size, and by how much
+
+        // Grab the minimum RTT seen during the last RTT
+        // Taking the min avoids the effects of delayed ACKs
+        // (though congestion may be noticed a bit later)
+        int rtt = _currentMinRTT;
+
+        uint64_t expectedWindowSize = _congestionWindowSize * _baseRTT / rtt;
+        uint64_t diff = _congestionWindowSize * (rtt - _baseRTT) / _baseRTT;
+
+        if (diff > VEGAS_GAMMA_SEGMENTS && isInSlowStart()) {
+            // we're going too fast, slow down and switch to congestion avoidance
+
+            // the congestion window should match the actual rate
+            _congestionWindowSize = std::min(_congestionWindowSize, expectedWindowSize + 1);
+            adjustSlowStartThreshold();
+
+        } else if (isInSlowStart()) {
+            // slow start
+            performSlowStart(ack);
+        } else {
+            // figure out where the congestion window should be
+            if (diff > VEGAS_BETA_SEGMENTS) {
+                // the old congestion window was too fast (difference > beta)
+                // so reduce it to slow down
+                --_congestionWindowSize;
+                adjustSlowStartThreshold();
+            } else if (diff < VEGAS_ALPHA_SEGMENTS) {
+                // there aren't enough packets on the wire, add more to the congestion window
+                ++_congestionWindowSize;
+            } else {
+                // sending rate seems good, no congestion window adjustment
+            }
+        }
+
+        // we never allow the congestion window to be smaller than two packets
+        static uint64_t VEGAS_CW_MIN_PACKETS = 2;
+        _congestionWindowSize = std::min(_congestionWindowSize, VEGAS_CW_MIN_PACKETS);
+
+//      _slowStartThreshold = currentSlowStartThreshold();
+
+    }
+
+    _lastRTTMaxSeqNum = _sendCurrSeqNum;
+
+    // reset our state for the next RTT
+    _currentMinRTT = std::numeric_limits<int>::max();
+    _numRTT = 0;
+}
+
+
+void TCPVegasCC::onPacketSent(int packetSize, SequenceNumber seqNum) {
+    _sentPacketTimes[seqNum] = { p_high_resolution_clock::now(), packetSize };
+}
+

libraries/networking/src/udt/TCPVegasCC.h

@@ -0,0 +1,59 @@
+//
+//  TCPVegasCC.h
+//  libraries/networking/src/udt
+//
+//  Created by Stephen Birarda on 2016-09-20.
+//  Copyright 2016 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#pragma once
+
+#ifndef hifi_TCPVegasCC_h
+#define hifi_TCPVegasCC_h
+
+#include <map>
+
+#include "CongestionControl.h"
+#include "Constants.h"
+#include "TCPRenoCC.h"
+
+namespace udt {
+    
+
+class TCPVegasCC : public TCPRenoCC {
+public:
+    TCPVegasCC() {};
+
+public:
+    virtual void onACK(SequenceNumber ackNum) override;
+    virtual void onLoss(SequenceNumber rangeStart, SequenceNumber rangeEnd) override {};
+    virtual void onTimeout() override {};
+    virtual void onPacketSent(int packetSize, SequenceNumber seqNum) override;
+    
+protected:
+    virtual void performCongestionAvoidance(SequenceNumber ack) override;
+private:
+    void adjustSlowStartThreshold()
+        { _slowStartThreshold = std::min(_slowStartThreshold, (uint32_t) _congestionWindowSize - 1); }
+
+    using TimeSizePair = std::pair<p_high_resolution_clock::time_point, int>;
+    using PacketTimeList = std::map<SequenceNumber, TimeSizePair>;
+    PacketTimeList _sentPacketTimes; // Map of sequence numbers to sent time
+
+    int _currentMinRTT { 0x7FFFFFFF }; // Current RTT, in microseconds
+    int _baseRTT { 0x7FFFFFFF }; // Lowest RTT during connection, in microseconds
+    int _numRTT { 0 }; // Number of RTT collected during last RTT
+
+    SequenceNumber _lastRTTMaxSeqNum; // Highest sent sequence number at time of last congestion window adjustment
+};
+
+}
+
+
+
+
+
+#endif // hifi_TCPVegasCC_h