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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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