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lines changed Original file line number Diff line number Diff line change
@@ -539,21 +539,10 @@ at that moment.
539 539 540 540
#### msRTT
541 541 542 -
Calculated Round trip time (RTT), in milliseconds. Sender and Receiver. \
543 -
The value is calculated by the receiver based on the incoming ACKACK control packets
544 -
(used by sender to acknowledge ACKs from receiver).
545 - 546 -
The RTT (Round-Trip time) is the sum of two STT (Single-Trip time)
547 -
values, one from agent to peer, and one from peer to agent. Note that **the
548 -
measurement method is different than in TCP**. SRT measures only the "reverse
549 -
RTT", that is, the time measured at the receiver between sending a `UMSG_ACK`
550 -
message until receiving the sender's `UMSG_ACKACK` response message (with the
551 -
same journal). This happens to be a little different from the "forward RTT"
552 -
measured in TCP, which is the time between sending a data packet of a particular
553 -
sequence number and receiving `UMSG_ACK` with a sequence number that is later
554 -
by 1. Forward RTT isn't being measured or reported in SRT, although some
555 -
research works have shown that these values, even though they should be the same,
556 -
happen to differ; "reverse RTT" seems to be more optimistic.
542 +
Smoothed round-trip time (SRTT), an exponentially-weighted moving average (EWMA) of an endpoint's RTT samples, in milliseconds.
543 +
Available both for sender and receiver.
544 + 545 +
See [Section 4.10. Round-Trip Time Estimation](https://tools.ietf.org/html/draft-sharabayko-srt-00#section-4.10) of the [SRT RFC](https://datatracker.ietf.org/doc/html/draft-sharabayko-srt-00) and [[RFC6298] Paxson, V., Allman, M., Chu, J., and M. Sargent, "Computing TCP's Retransmission Timer"](https://datatracker.ietf.org/doc/html/rfc6298) for more details.
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#### mbpsBandwidth
559 548
@@ -50,14 +50,14 @@ using namespace std;
50 50
CInfoBlock& CInfoBlock::copyFrom(const CInfoBlock& obj)
51 51
{
52 52
std::copy(obj.m_piIP, obj.m_piIP + 4, m_piIP);
53 -
m_iIPversion = obj.m_iIPversion;
54 -
m_ullTimeStamp = obj.m_ullTimeStamp;
55 -
m_iRTT = obj.m_iRTT;
56 -
m_iBandwidth = obj.m_iBandwidth;
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m_iLossRate = obj.m_iLossRate;
53 +
m_iIPversion = obj.m_iIPversion;
54 +
m_ullTimeStamp = obj.m_ullTimeStamp;
55 +
m_iSRTT = obj.m_iSRTT;
56 +
m_iBandwidth = obj.m_iBandwidth;
57 +
m_iLossRate = obj.m_iLossRate;
58 58
m_iReorderDistance = obj.m_iReorderDistance;
59 -
m_dInterval = obj.m_dInterval;
60 -
m_dCWnd = obj.m_dCWnd;
59 +
m_dInterval = obj.m_dInterval;
60 +
m_dCWnd = obj.m_dCWnd;
61 61 62 62
return *this;
63 63
}
@@ -84,14 +84,14 @@ CInfoBlock* CInfoBlock::clone()
84 84
CInfoBlock* obj = new CInfoBlock;
85 85 86 86
std::copy(m_piIP, m_piIP + 4, obj->m_piIP);
87 -
obj->m_iIPversion = m_iIPversion;
88 -
obj->m_ullTimeStamp = m_ullTimeStamp;
89 -
obj->m_iRTT = m_iRTT;
90 -
obj->m_iBandwidth = m_iBandwidth;
91 -
obj->m_iLossRate = m_iLossRate;
87 +
obj->m_iIPversion = m_iIPversion;
88 +
obj->m_ullTimeStamp = m_ullTimeStamp;
89 +
obj->m_iSRTT = m_iSRTT;
90 +
obj->m_iBandwidth = m_iBandwidth;
91 +
obj->m_iLossRate = m_iLossRate;
92 92
obj->m_iReorderDistance = m_iReorderDistance;
93 -
obj->m_dInterval = m_dInterval;
94 -
obj->m_dCWnd = m_dCWnd;
93 +
obj->m_dInterval = m_dInterval;
94 +
obj->m_dCWnd = m_dCWnd;
95 95 96 96
return obj;
97 97
}
@@ -235,15 +235,15 @@ template<typename T> class CCache
235 235
class CInfoBlock
236 236
{
237 237
public:
238 -
uint32_t m_piIP[4]; // IP address, machine read only, not human readable format
239 -
int m_iIPversion; // Address family: AF_INET or AF_INET6
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uint64_t m_ullTimeStamp; // last update time
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int m_iRTT; // RTT
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int m_iBandwidth; // estimated bandwidth
243 -
int m_iLossRate; // average loss rate
244 -
int m_iReorderDistance; // packet reordering distance
245 -
double m_dInterval; // inter-packet time, congestion control
246 -
double m_dCWnd; // congestion window size, congestion control
238 +
uint32_t m_piIP[4]; // IP address, machine read only, not human readable format.
239 +
int m_iIPversion; // Address family: AF_INET or AF_INET6.
240 +
uint64_t m_ullTimeStamp; // Last update time.
241 +
int m_iSRTT; // Smoothed RTT.
242 +
int m_iBandwidth; // Estimated link bandwidth.
243 +
int m_iLossRate; // Average loss rate.
244 +
int m_iReorderDistance; // Packet reordering distance.
245 +
double m_dInterval; // Inter-packet time (Congestion Control).
246 +
double m_dCWnd; // Congestion window size (Congestion Control).
247 247 248 248
public:
249 249
CInfoBlock() {} // NOTE: leaves uninitialized
@@ -284,7 +284,7 @@ enum ETransmissionEvent
284 284
{
285 285
TEV_INIT, // --> After creation, and after any parameters were updated.
286 286
TEV_ACK, // --> When handling UMSG_ACK - older CCC:onAck()
287 -
TEV_ACKACK, // --> UDT does only RTT sync, can be read from CUDT::RTT().
287 +
TEV_ACKACK, // --> UDT does only RTT sync, can be read from CUDT::SRTT().
288 288
TEV_LOSSREPORT, // --> When handling UMSG_LOSSREPORT - older CCC::onLoss()
289 289
TEV_CHECKTIMER, // --> See TEV_CHT_REXMIT
290 290
TEV_SEND, // --> When the packet is scheduled for sending - older CCC::onPktSent
@@ -358,11 +358,11 @@ class FileCC : public SrtCongestionControlBase
358 358
}
359 359
else
360 360
{
361 -
m_dPktSndPeriod = m_dCWndSize / (m_parent->RTT() + m_iRCInterval);
361 +
m_dPktSndPeriod = m_dCWndSize / (m_parent->SRTT() + m_iRCInterval);
362 362
HLOGC(cclog.Debug, log << "FileCC: UPD (slowstart:ENDED) wndsize="
363 363
<< m_dCWndSize << "/" << m_dMaxCWndSize
364 364
<< " sndperiod=" << m_dPktSndPeriod << "us = wndsize/(RTT+RCIV) RTT="
365 -
<< m_parent->RTT() << " RCIV=" << m_iRCInterval);
365 +
<< m_parent->SRTT() << " RCIV=" << m_iRCInterval);
366 366
}
367 367
}
368 368
else
@@ -374,9 +374,9 @@ class FileCC : public SrtCongestionControlBase
374 374
}
375 375
else
376 376
{
377 -
m_dCWndSize = m_parent->deliveryRate() / 1000000.0 * (m_parent->RTT() + m_iRCInterval) + 16;
377 +
m_dCWndSize = m_parent->deliveryRate() / 1000000.0 * (m_parent->SRTT() + m_iRCInterval) + 16;
378 378
HLOGC(cclog.Debug, log << "FileCC: UPD (speed mode) wndsize="
379 -
<< m_dCWndSize << "/" << m_dMaxCWndSize << " RTT = " << m_parent->RTT()
379 +
<< m_dCWndSize << "/" << m_dMaxCWndSize << " RTT = " << m_parent->SRTT()
380 380
<< " sndperiod=" << m_dPktSndPeriod << "us. deliverRate = "
381 381
<< m_parent->deliveryRate() << " pkts/s)");
382 382
}
@@ -481,17 +481,17 @@ class FileCC : public SrtCongestionControlBase
481 481
}
482 482
else
483 483
{
484 -
m_dPktSndPeriod = m_dCWndSize / (m_parent->RTT() + m_iRCInterval);
484 +
m_dPktSndPeriod = m_dCWndSize / (m_parent->SRTT() + m_iRCInterval);
485 485
HLOGC(cclog.Debug, log << "FileCC: LOSS, SLOWSTART:OFF, sndperiod=" << m_dPktSndPeriod << "us AS wndsize/(RTT+RCIV) (RTT="
486 -
<< m_parent->RTT() << " RCIV=" << m_iRCInterval << ")");
486 +
<< m_parent->SRTT() << " RCIV=" << m_iRCInterval << ")");
487 487
}
488 488 489 489
}
490 490 491 491
m_bLoss = true;
492 492 493 493
// TODO: const int pktsInFlight = CSeqNo::seqoff(m_iLastAck, m_parent->sndSeqNo());
494 -
const int pktsInFlight = m_parent->RTT() / m_dPktSndPeriod;
494 +
const int pktsInFlight = m_parent->SRTT() / m_dPktSndPeriod;
495 495
const int numPktsLost = m_parent->sndLossLength();
496 496
const int lost_pcent_x10 = pktsInFlight > 0 ? (numPktsLost * 1000) / pktsInFlight : 0;
497 497
@@ -581,9 +581,9 @@ class FileCC : public SrtCongestionControlBase
581 581
}
582 582
else
583 583
{
584 -
m_dPktSndPeriod = m_dCWndSize / (m_parent->RTT() + m_iRCInterval);
584 +
m_dPktSndPeriod = m_dCWndSize / (m_parent->SRTT() + m_iRCInterval);
585 585
HLOGC(cclog.Debug, log << "FileCC: CHKTIMER, SLOWSTART:OFF, sndperiod=" << m_dPktSndPeriod << "us AS wndsize/(RTT+RCIV) (wndsize="
586 -
<< setprecision(6) << m_dCWndSize << " RTT=" << m_parent->RTT() << " RCIV=" << m_iRCInterval << ")");
586 +
<< setprecision(6) << m_dCWndSize << " RTT=" << m_parent->SRTT() << " RCIV=" << m_iRCInterval << ")");
587 587
}
588 588
}
589 589
else
@@ -146,7 +146,7 @@ class SrtCongestionControlBase
146 146
//int m_iMSS; // NOT REQUIRED. Use m_parent->MSS() instead.
147 147
//int32_t m_iSndCurrSeqNo; // NOT REQUIRED. Use m_parent->sndSeqNo().
148 148
//int m_iRcvRate; // NOT REQUIRED. Use m_parent->deliveryRate() instead.
149 -
//int m_RTT; // NOT REQUIRED. Use m_parent->RTT() instead.
149 +
//int m_RTT; // NOT REQUIRED. Use m_parent->SRTT() instead.
150 150
//char* m_pcParam; // Used to access m_llMaxBw. Use m_parent->maxBandwidth() instead.
151 151 152 152
// Constructor in protected section so that this class is semi-abstract.
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