1// Copyright 2014 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#include "net/quic/congestion_control/time_loss_algorithm.h" 6 7#include "net/quic/congestion_control/rtt_stats.h" 8#include "net/quic/quic_protocol.h" 9 10namespace net { 11namespace { 12 13// The minimum delay before a packet will be considered lost, 14// regardless of SRTT. Half of the minimum TLP, since the loss algorithm only 15// triggers when a nack has been receieved for the packet. 16static const size_t kMinLossDelayMs = 5; 17 18// How many RTTs the algorithm waits before determining a packet is lost. 19static const double kLossDelayMultiplier = 1.25; 20 21} // namespace 22 23TimeLossAlgorithm::TimeLossAlgorithm() 24 : loss_detection_timeout_(QuicTime::Zero()) { } 25 26LossDetectionType TimeLossAlgorithm::GetLossDetectionType() const { 27 return kTime; 28} 29 30SequenceNumberSet TimeLossAlgorithm::DetectLostPackets( 31 const QuicUnackedPacketMap& unacked_packets, 32 const QuicTime& time, 33 QuicPacketSequenceNumber largest_observed, 34 const RttStats& rtt_stats) { 35 SequenceNumberSet lost_packets; 36 loss_detection_timeout_ = QuicTime::Zero(); 37 QuicTime::Delta loss_delay = QuicTime::Delta::Max( 38 QuicTime::Delta::FromMilliseconds(kMinLossDelayMs), 39 QuicTime::Delta::Max(rtt_stats.SmoothedRtt(), rtt_stats.latest_rtt()) 40 .Multiply(kLossDelayMultiplier)); 41 42 QuicPacketSequenceNumber sequence_number = unacked_packets.GetLeastUnacked(); 43 for (QuicUnackedPacketMap::const_iterator it = unacked_packets.begin(); 44 it != unacked_packets.end() && sequence_number <= largest_observed; 45 ++it, ++sequence_number) { 46 if (!it->in_flight) { 47 continue; 48 } 49 LOG_IF(DFATAL, it->nack_count == 0) 50 << "All packets less than largest observed should have been nacked."; 51 52 // Packets are sent in order, so break when we haven't waited long enough 53 // to lose any more packets and leave the loss_time_ set for the timeout. 54 QuicTime when_lost = it->sent_time.Add(loss_delay); 55 if (time < when_lost) { 56 loss_detection_timeout_ = when_lost; 57 break; 58 } 59 lost_packets.insert(sequence_number); 60 } 61 62 return lost_packets; 63} 64 65// loss_time_ is updated in DetectLostPackets, which must be called every time 66// an ack is received or the timeout expires. 67QuicTime TimeLossAlgorithm::GetLossTimeout() const { 68 return loss_detection_timeout_; 69} 70 71} // namespace net 72