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| 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 | |
| 10 namespace net { | |
| 11 namespace { | |
| 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. | |
| 16 static const size_t kMinLossDelayMs = 5; | |
| 17 | |
| 18 // How many RTTs the algorithm waits before determining a packet is lost. | |
| 19 static const double kLossDelayMultiplier = 1.25; | |
| 20 | |
| 21 } // namespace | |
| 22 | |
| 23 TimeLossAlgorithm::TimeLossAlgorithm() | |
| 24 : loss_detection_timeout_(QuicTime::Zero()) { } | |
| 25 | |
| 26 LossDetectionType TimeLossAlgorithm::GetLossDetectionType() const { | |
| 27 return kTime; | |
| 28 } | |
| 29 | |
| 30 SequenceNumberSet 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.smoothed_rtt(), 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 && it->sent_time.IsInitialized()) | |
| 50 << "All packets less than largest observed should have been nacked." | |
| 51 << "sequence_number:" << sequence_number | |
| 52 << " largest_observed:" << largest_observed; | |
| 53 | |
| 54 // Packets are sent in order, so break when we haven't waited long enough | |
| 55 // to lose any more packets and leave the loss_time_ set for the timeout. | |
| 56 QuicTime when_lost = it->sent_time.Add(loss_delay); | |
| 57 if (time < when_lost) { | |
| 58 loss_detection_timeout_ = when_lost; | |
| 59 break; | |
| 60 } | |
| 61 lost_packets.insert(sequence_number); | |
| 62 } | |
| 63 | |
| 64 return lost_packets; | |
| 65 } | |
| 66 | |
| 67 // loss_time_ is updated in DetectLostPackets, which must be called every time | |
| 68 // an ack is received or the timeout expires. | |
| 69 QuicTime TimeLossAlgorithm::GetLossTimeout() const { | |
| 70 return loss_detection_timeout_; | |
| 71 } | |
| 72 | |
| 73 } // namespace net | |
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