3 * congestion control logic for the swift protocol
5 * Created by Victor Grishchenko on 12/10/09.
6 * Copyright 2009 Delft University of Technology. All rights reserved.
12 using namespace swift;
15 tint Channel::MIN_DEV = 50*TINT_MSEC;
16 tint Channel::MAX_SEND_INTERVAL = TINT_SEC*58;
17 tint Channel::LEDBAT_TARGET = TINT_MSEC*25;
18 float Channel::LEDBAT_GAIN = 1.0/LEDBAT_TARGET;
19 tint Channel::LEDBAT_DELAY_BIN = TINT_SEC*30;
20 const char* Channel::SEND_CONTROL_MODES[] = {"keepalive", "pingpong",
21 "slowstart", "standard_aimd", "ledbat"};
24 tint Channel::NextSendTime () {
25 switch (send_control_) {
26 case KEEP_ALIVE_CONTROL: return KeepAliveNextSendTime();
27 case PING_PONG_CONTROL: return PingPongNextSendTime();
28 case SLOW_START_CONTROL: return SlowStartNextSendTime();
29 case AIMD_CONTROL: return AimdNextSendTime();
30 case LEDBAT_CONTROL: return LedbatNextSendTime();
31 case CLOSE_CONTROL: return TINT_NEVER;
32 default: assert(false);
36 tint Channel::SwitchSendControl (int control_mode) {
37 dprintf("%s #%u sendctrl switch %s->%s\n",tintstr(),id(),
38 SEND_CONTROL_MODES[send_control_],SEND_CONTROL_MODES[control_mode]);
39 switch (control_mode) {
40 case KEEP_ALIVE_CONTROL:
41 send_interval_ = max(TINT_SEC/10,rtt_avg_);
42 dev_avg_ = max(TINT_SEC,rtt_avg_);
43 data_out_cap_ = bin64_t::ALL;
46 case PING_PONG_CONTROL:
47 dev_avg_ = max(TINT_SEC,rtt_avg_);
48 data_out_cap_ = bin64_t::ALL;
51 case SLOW_START_CONTROL:
63 send_control_ = control_mode;
64 return NextSendTime();
67 tint Channel::KeepAliveNextSendTime () {
68 if (sent_since_recv_>=3 && last_recv_time_<NOW-TINT_MIN)
69 return SwitchSendControl(CLOSE_CONTROL);
71 return SwitchSendControl(SLOW_START_CONTROL);
72 if (data_in_.time!=TINT_NEVER)
75 if (send_interval_>MAX_SEND_INTERVAL)
76 send_interval_ = MAX_SEND_INTERVAL;
77 return last_send_time_ + send_interval_;
80 tint Channel::PingPongNextSendTime () { // FIXME INFINITE LOOP
82 return SwitchSendControl(KEEP_ALIVE_CONTROL);
84 return SwitchSendControl(SLOW_START_CONTROL);
85 if (data_in_.time!=TINT_NEVER)
87 if (last_recv_time_>last_send_time_)
91 return last_send_time_ + ack_timeout(); // timeout
94 tint Channel::CwndRateNextSendTime () {
95 if (data_in_.time!=TINT_NEVER)
96 return NOW; // TODO: delayed ACKs
97 //if (last_recv_time_<NOW-rtt_avg_*4)
98 // return SwitchSendControl(KEEP_ALIVE_CONTROL);
99 send_interval_ = rtt_avg_/cwnd_;
100 if (send_interval_>std::max(rtt_avg_,TINT_SEC)*4)
101 return SwitchSendControl(KEEP_ALIVE_CONTROL);
102 if (data_out_.size()<cwnd_) {
103 dprintf("%s #%u sendctrl next in %llius\n",tintstr(),id_,send_interval_);
104 return last_data_out_time_ + send_interval_;
106 assert(data_out_.front().time!=TINT_NEVER);
107 return data_out_.front().time + ack_timeout();
111 void Channel::BackOffOnLosses (float ratio) {
112 ack_rcvd_recent_ = 0;
113 ack_not_rcvd_recent_ = 0;
114 if (last_loss_time_<NOW-rtt_avg_) {
116 last_loss_time_ = NOW;
117 dprintf("%s #%u sendctrl backoff %3.2f\n",tintstr(),id_,cwnd_);
121 tint Channel::SlowStartNextSendTime () {
122 if (ack_not_rcvd_recent_) {
124 return SwitchSendControl(LEDBAT_CONTROL);//AIMD_CONTROL);
126 if (rtt_avg_/cwnd_<TINT_SEC/10)
127 return SwitchSendControl(LEDBAT_CONTROL);//AIMD_CONTROL);
128 cwnd_+=ack_rcvd_recent_;
130 return CwndRateNextSendTime();
133 tint Channel::AimdNextSendTime () {
134 if (ack_not_rcvd_recent_)
136 if (ack_rcvd_recent_) {
138 cwnd_ += ack_rcvd_recent_/cwnd_;
143 return CwndRateNextSendTime();
146 tint Channel::LedbatNextSendTime () {
147 tint owd_cur(TINT_NEVER), owd_min(TINT_NEVER);
148 for(int i=0; i<4; i++) {
149 if (owd_min>owd_min_bins_[i])
150 owd_min = owd_min_bins_[i];
151 if (owd_cur>owd_current_[i])
152 owd_cur = owd_current_[i];
154 if (ack_not_rcvd_recent_)
155 BackOffOnLosses(0.8);
156 ack_rcvd_recent_ = 0;
157 tint queueing_delay = owd_cur - owd_min;
158 tint off_target = LEDBAT_TARGET - queueing_delay;
159 cwnd_ += LEDBAT_GAIN * off_target / cwnd_;
160 dprintf("%s #%u sendctrl ledbat %lli-%lli => %3.2f\n",
161 tintstr(),id_,owd_cur,owd_min,cwnd_);
162 return CwndRateNextSendTime();