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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 // | 4 // |
5 // Cubic algorithm, helper class to TCP cubic. | 5 // Cubic algorithm, helper class to TCP cubic. |
6 // For details see http://netsrv.csc.ncsu.edu/export/cubic_a_new_tcp_2008.pdf. | 6 // For details see http://netsrv.csc.ncsu.edu/export/cubic_a_new_tcp_2008.pdf. |
7 | 7 |
8 #ifndef NET_QUIC_CONGESTION_CONTROL_CUBIC_H_ | 8 #ifndef NET_QUIC_CONGESTION_CONTROL_CUBIC_H_ |
9 #define NET_QUIC_CONGESTION_CONTROL_CUBIC_H_ | 9 #define NET_QUIC_CONGESTION_CONTROL_CUBIC_H_ |
10 | 10 |
11 #include "base/basictypes.h" | 11 #include "base/basictypes.h" |
12 #include "net/base/net_export.h" | 12 #include "net/base/net_export.h" |
13 #include "net/quic/quic_bandwidth.h" | 13 #include "net/quic/quic_bandwidth.h" |
14 #include "net/quic/quic_clock.h" | 14 #include "net/quic/quic_clock.h" |
15 #include "net/quic/quic_connection_stats.h" | 15 #include "net/quic/quic_connection_stats.h" |
16 #include "net/quic/quic_time.h" | 16 #include "net/quic/quic_time.h" |
17 | 17 |
18 namespace net { | 18 namespace net { |
19 | 19 |
20 class NET_EXPORT_PRIVATE Cubic { | 20 class NET_EXPORT_PRIVATE Cubic { |
21 public: | 21 public: |
22 Cubic(const QuicClock* clock, QuicConnectionStats* stats); | 22 explicit Cubic(const QuicClock* clock); |
23 | 23 |
24 void SetNumConnections(int num_connections); | 24 void SetNumConnections(int num_connections); |
25 | 25 |
26 // Call after a timeout to reset the cubic state. | 26 // Call after a timeout to reset the cubic state. |
27 void Reset(); | 27 void Reset(); |
28 | 28 |
29 // Compute a new congestion window to use after a loss event. | 29 // Compute a new congestion window to use after a loss event. |
30 // Returns the new congestion window in packets. The new congestion window is | 30 // Returns the new congestion window in packets. The new congestion window is |
31 // a multiplicative decrease of our current window. | 31 // a multiplicative decrease of our current window. |
32 QuicPacketCount CongestionWindowAfterPacketLoss(QuicPacketCount current); | 32 QuicPacketCount CongestionWindowAfterPacketLoss(QuicPacketCount current); |
33 | 33 |
34 // Compute a new congestion window to use after a received ACK. | 34 // Compute a new congestion window to use after a received ACK. |
35 // Returns the new congestion window in packets. The new congestion window | 35 // Returns the new congestion window in packets. The new congestion window |
36 // follows a cubic function that depends on the time passed since last | 36 // follows a cubic function that depends on the time passed since last |
37 // packet loss. | 37 // packet loss. |
38 QuicPacketCount CongestionWindowAfterAck(QuicPacketCount current, | 38 QuicPacketCount CongestionWindowAfterAck(QuicPacketCount current, |
39 QuicTime::Delta delay_min); | 39 QuicTime::Delta delay_min); |
40 | 40 |
41 private: | 41 private: |
42 static const QuicTime::Delta MaxCubicTimeInterval() { | 42 static const QuicTime::Delta MaxCubicTimeInterval() { |
43 return QuicTime::Delta::FromMilliseconds(30); | 43 return QuicTime::Delta::FromMilliseconds(30); |
44 } | 44 } |
45 | 45 |
46 // Compute the TCP Cubic alpha and beta based on the current number of | 46 // Compute the TCP Cubic alpha and beta based on the current number of |
47 // connections. | 47 // connections. |
48 float Alpha() const; | 48 float Alpha() const; |
49 float Beta() const; | 49 float Beta() const; |
50 | 50 |
51 // Update congestion control variables in QuicConnectionStats. | |
52 void UpdateCongestionControlStats(QuicPacketCount new_cubic_mode_cwnd, | |
53 QuicPacketCount new_reno_mode_cwnd); | |
54 const QuicClock* clock_; | 51 const QuicClock* clock_; |
55 | 52 |
56 // Number of connections to simulate. | 53 // Number of connections to simulate. |
57 int num_connections_; | 54 int num_connections_; |
58 | 55 |
59 // Time when this cycle started, after last loss event. | 56 // Time when this cycle started, after last loss event. |
60 QuicTime epoch_; | 57 QuicTime epoch_; |
61 | 58 |
62 // Time when we updated last_congestion_window. | 59 // Time when we updated last_congestion_window. |
63 QuicTime last_update_time_; | 60 QuicTime last_update_time_; |
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78 | 75 |
79 // Origin point of cubic function. | 76 // Origin point of cubic function. |
80 QuicPacketCount origin_point_congestion_window_; | 77 QuicPacketCount origin_point_congestion_window_; |
81 | 78 |
82 // Time to origin point of cubic function in 2^10 fractions of a second. | 79 // Time to origin point of cubic function in 2^10 fractions of a second. |
83 uint32 time_to_origin_point_; | 80 uint32 time_to_origin_point_; |
84 | 81 |
85 // Last congestion window in packets computed by cubic function. | 82 // Last congestion window in packets computed by cubic function. |
86 QuicPacketCount last_target_congestion_window_; | 83 QuicPacketCount last_target_congestion_window_; |
87 | 84 |
88 // QuicConnectionStats includes congestion control related stats. | |
89 QuicConnectionStats* stats_; | |
90 | |
91 DISALLOW_COPY_AND_ASSIGN(Cubic); | 85 DISALLOW_COPY_AND_ASSIGN(Cubic); |
92 }; | 86 }; |
93 | 87 |
94 } // namespace net | 88 } // namespace net |
95 | 89 |
96 #endif // NET_QUIC_CONGESTION_CONTROL_CUBIC_H_ | 90 #endif // NET_QUIC_CONGESTION_CONTROL_CUBIC_H_ |
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