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 default: assert(false);
35 tint Channel::SwitchSendControl (int control_mode) {
36 dprintf("%s #%u sendctrl switch %s->%s\n",tintstr(),id(),
37 SEND_CONTROL_MODES[send_control_],SEND_CONTROL_MODES[control_mode]);
38 switch (control_mode) {
39 case KEEP_ALIVE_CONTROL:
40 send_interval_ = max(TINT_SEC/10,rtt_avg_);
41 dev_avg_ = max(TINT_SEC,rtt_avg_);
42 data_out_cap_ = bin64_t::ALL;
45 case PING_PONG_CONTROL:
46 dev_avg_ = max(TINT_SEC,rtt_avg_);
47 data_out_cap_ = bin64_t::ALL;
50 case SLOW_START_CONTROL:
60 send_control_ = control_mode;
61 return NextSendTime();
64 tint Channel::KeepAliveNextSendTime () {
65 if (sent_since_recv_>=3 && last_recv_time_<NOW-TINT_MIN)
68 return SwitchSendControl(SLOW_START_CONTROL);
69 if (data_in_.time!=TINT_NEVER)
72 if (send_interval_>MAX_SEND_INTERVAL)
73 send_interval_ = MAX_SEND_INTERVAL;
74 return last_send_time_ + send_interval_;
77 tint Channel::PingPongNextSendTime () { // FIXME INFINITE LOOP
79 return SwitchSendControl(KEEP_ALIVE_CONTROL);
81 return SwitchSendControl(SLOW_START_CONTROL);
82 if (data_in_.time!=TINT_NEVER)
84 if (last_recv_time_>last_send_time_)
88 return last_send_time_ + ack_timeout(); // timeout
91 tint Channel::CwndRateNextSendTime () {
92 if (data_in_.time!=TINT_NEVER)
93 return NOW; // TODO: delayed ACKs
94 //if (last_recv_time_<NOW-rtt_avg_*4)
95 // return SwitchSendControl(KEEP_ALIVE_CONTROL);
96 send_interval_ = rtt_avg_/cwnd_;
97 if (send_interval_>std::max(rtt_avg_,TINT_SEC)*4)
98 return SwitchSendControl(KEEP_ALIVE_CONTROL);
99 if (data_out_.size()<cwnd_) {
100 dprintf("%s #%u sendctrl next in %llius\n",tintstr(),id_,send_interval_);
101 return last_data_out_time_ + send_interval_;
103 assert(data_out_.front().time!=TINT_NEVER);
104 return data_out_.front().time + ack_timeout();
108 void Channel::BackOffOnLosses (float ratio) {
109 ack_rcvd_recent_ = 0;
110 ack_not_rcvd_recent_ = 0;
111 if (last_loss_time_<NOW-rtt_avg_) {
113 last_loss_time_ = NOW;
114 dprintf("%s #%u sendctrl backoff %3.2f\n",tintstr(),id_,cwnd_);
118 tint Channel::SlowStartNextSendTime () {
119 if (ack_not_rcvd_recent_) {
121 return SwitchSendControl(LEDBAT_CONTROL);//AIMD_CONTROL);
123 if (rtt_avg_/cwnd_<TINT_SEC/10)
124 return SwitchSendControl(LEDBAT_CONTROL);//AIMD_CONTROL);
125 cwnd_+=ack_rcvd_recent_;
127 return CwndRateNextSendTime();
130 tint Channel::AimdNextSendTime () {
131 if (ack_not_rcvd_recent_)
133 if (ack_rcvd_recent_) {
135 cwnd_ += ack_rcvd_recent_/cwnd_;
140 return CwndRateNextSendTime();
143 tint Channel::LedbatNextSendTime () {
144 tint owd_cur(TINT_NEVER), owd_min(TINT_NEVER);
145 for(int i=0; i<4; i++) {
146 if (owd_min>owd_min_bins_[i])
147 owd_min = owd_min_bins_[i];
148 if (owd_cur>owd_current_[i])
149 owd_cur = owd_current_[i];
151 if (ack_not_rcvd_recent_)
152 BackOffOnLosses(0.8);
153 ack_rcvd_recent_ = 0;
154 tint queueing_delay = owd_cur - owd_min;
155 tint off_target = LEDBAT_TARGET - queueing_delay;
156 cwnd_ += LEDBAT_GAIN * off_target / cwnd_;
157 dprintf("%s #%u sendctrl ledbat %lli-%lli => %3.2f\n",
158 tintstr(),id_,owd_cur,owd_min,cwnd_);
159 return CwndRateNextSendTime();