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 tint Channel::MAX_POSSIBLE_RTT = TINT_SEC*10;
21 const char* Channel::SEND_CONTROL_MODES[] = {"keepalive", "pingpong",
22 "slowstart", "standard_aimd", "ledbat", "closing"};
25 tint Channel::NextSendTime () {
26 switch (send_control_) {
27 case KEEP_ALIVE_CONTROL: return KeepAliveNextSendTime();
28 case PING_PONG_CONTROL: return PingPongNextSendTime();
29 case SLOW_START_CONTROL: return SlowStartNextSendTime();
30 case AIMD_CONTROL: return AimdNextSendTime();
31 case LEDBAT_CONTROL: return LedbatNextSendTime();
32 case CLOSE_CONTROL: return TINT_NEVER;
33 default: assert(false);
37 tint Channel::SwitchSendControl (int control_mode) {
38 dprintf("%s #%u sendctrl switch %s->%s\n",tintstr(),id(),
39 SEND_CONTROL_MODES[send_control_],SEND_CONTROL_MODES[control_mode]);
40 switch (control_mode) {
41 case KEEP_ALIVE_CONTROL:
42 send_interval_ = max(TINT_SEC/10,rtt_avg_);
43 dev_avg_ = max(TINT_SEC,rtt_avg_);
44 data_out_cap_ = bin64_t::ALL;
47 case PING_PONG_CONTROL:
48 dev_avg_ = max(TINT_SEC,rtt_avg_);
49 data_out_cap_ = bin64_t::ALL;
52 case SLOW_START_CONTROL:
64 send_control_ = control_mode;
65 return NextSendTime();
68 tint Channel::KeepAliveNextSendTime () {
69 if (sent_since_recv_>=3 && last_recv_time_<NOW-TINT_MIN)
70 return SwitchSendControl(CLOSE_CONTROL);
72 return SwitchSendControl(SLOW_START_CONTROL);
73 if (data_in_.time!=TINT_NEVER)
76 if (send_interval_>MAX_SEND_INTERVAL)
77 send_interval_ = MAX_SEND_INTERVAL;
78 return last_send_time_ + send_interval_;
81 tint Channel::PingPongNextSendTime () { // FIXME INFINITE LOOP
83 return SwitchSendControl(KEEP_ALIVE_CONTROL);
85 return SwitchSendControl(SLOW_START_CONTROL);
86 if (data_in_.time!=TINT_NEVER)
88 if (last_recv_time_>last_send_time_)
92 return last_send_time_ + ack_timeout(); // timeout
95 tint Channel::CwndRateNextSendTime () {
96 if (data_in_.time!=TINT_NEVER)
97 return NOW; // TODO: delayed ACKs
98 //if (last_recv_time_<NOW-rtt_avg_*4)
99 // return SwitchSendControl(KEEP_ALIVE_CONTROL);
100 send_interval_ = rtt_avg_/cwnd_;
101 if (send_interval_>max(rtt_avg_,TINT_SEC)*4)
102 return SwitchSendControl(KEEP_ALIVE_CONTROL);
103 if (data_out_.size()<cwnd_) {
104 dprintf("%s #%u sendctrl next in %llius (cwnd %.2f, data_out %i)\n",
105 tintstr(),id_,send_interval_,cwnd_,(int)data_out_.size());
106 return last_data_out_time_ + send_interval_;
108 assert(data_out_.front().time!=TINT_NEVER);
109 return data_out_.front().time + ack_timeout();
113 void Channel::BackOffOnLosses (float ratio) {
114 ack_rcvd_recent_ = 0;
115 ack_not_rcvd_recent_ = 0;
116 if (last_loss_time_<NOW-rtt_avg_) {
118 last_loss_time_ = NOW;
119 dprintf("%s #%u sendctrl backoff %3.2f\n",tintstr(),id_,cwnd_);
123 tint Channel::SlowStartNextSendTime () {
124 if (ack_not_rcvd_recent_) {
126 return SwitchSendControl(LEDBAT_CONTROL);//AIMD_CONTROL);
128 if (rtt_avg_/cwnd_<TINT_SEC/10)
129 return SwitchSendControl(LEDBAT_CONTROL);//AIMD_CONTROL);
130 cwnd_+=ack_rcvd_recent_;
132 return CwndRateNextSendTime();
135 tint Channel::AimdNextSendTime () {
136 if (ack_not_rcvd_recent_)
138 if (ack_rcvd_recent_) {
140 cwnd_ += ack_rcvd_recent_/cwnd_;
145 return CwndRateNextSendTime();
148 tint Channel::LedbatNextSendTime () {
149 tint owd_cur(TINT_NEVER), owd_min(TINT_NEVER);
150 for(int i=0; i<4; i++) {
151 if (owd_min>owd_min_bins_[i])
152 owd_min = owd_min_bins_[i];
153 if (owd_cur>owd_current_[i])
154 owd_cur = owd_current_[i];
156 if (ack_not_rcvd_recent_)
157 BackOffOnLosses(0.8);
158 ack_rcvd_recent_ = 0;
159 tint queueing_delay = owd_cur - owd_min;
160 tint off_target = LEDBAT_TARGET - queueing_delay;
161 cwnd_ += LEDBAT_GAIN * off_target / cwnd_;
164 if (owd_cur==TINT_NEVER || owd_min==TINT_NEVER)
166 dprintf("%s #%u sendctrl ledbat %lli-%lli => %3.2f\n",
167 tintstr(),id_,owd_cur,owd_min,cwnd_);
168 return CwndRateNextSendTime();