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/*
* Copyright (c) 2017-2019 Cisco and/or its affiliates.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <protocols/rtc_data_path.h>
#include <cfloat>
#include <chrono>
#define MAX_ROUNDS_WITHOUT_PKTS 10 // 2sec
namespace transport {
namespace protocol {
RTCDataPath::RTCDataPath()
: min_rtt(UINT_MAX),
prev_min_rtt(UINT_MAX),
min_owd(INT_MAX), // this is computed like in LEDBAT, so it is not the
// real OWD, but the measured one, that depends on the
// clock of sender and receiver. the only meaningful
// value is is the queueing delay. for this reason we
// keep both RTT (for the windowd calculation) and OWD
// (for congestion/quality control)
prev_min_owd(INT_MAX),
avg_owd(0.0),
queuing_delay(DBL_MAX),
lastRecvSeq_(0),
lastRecvTime_(0),
avg_inter_arrival_(DBL_MAX),
received_nacks_(false),
received_packets_(false),
rounds_without_packets_(0),
RTThistory_(HISTORY_LEN),
OWDhistory_(HISTORY_LEN){};
void RTCDataPath::insertRttSample(uint64_t rtt) {
// for the rtt we only keep track of the min one
if (rtt < min_rtt) min_rtt = rtt;
}
void RTCDataPath::insertOwdSample(int64_t owd) {
// for owd we use both min and avg
if (owd < min_owd) min_owd = owd;
if (avg_owd != DBL_MAX)
avg_owd = (avg_owd * (1 - ALPHA_RTC)) + (owd * ALPHA_RTC);
else {
avg_owd = owd;
}
// owd is computed only for valid data packets so we count only
// this for decide if we recevie traffic or not
received_packets_ = true;
}
void RTCDataPath::computeInterArrivalGap(uint32_t segmentNumber) {
// got packet in sequence, compute gap
if (lastRecvSeq_ == (segmentNumber - 1)) {
uint64_t now = std::chrono::duration_cast<std::chrono::milliseconds>(
std::chrono::steady_clock::now().time_since_epoch())
.count();
uint64_t delta = now - lastRecvTime_;
lastRecvSeq_ = segmentNumber;
lastRecvTime_ = now;
if (avg_inter_arrival_ == DBL_MAX)
avg_inter_arrival_ = delta;
else
avg_inter_arrival_ =
(avg_inter_arrival_ * (1 - ALPHA_RTC)) + (delta * ALPHA_RTC);
return;
}
// ooo packet, update the stasts if needed
if (lastRecvSeq_ <= segmentNumber) {
lastRecvSeq_ = segmentNumber;
lastRecvTime_ = std::chrono::duration_cast<std::chrono::milliseconds>(
std::chrono::steady_clock::now().time_since_epoch())
.count();
}
}
void RTCDataPath::receivedNack() { received_nacks_ = true; }
double RTCDataPath::getInterArrivalGap() {
if (avg_inter_arrival_ == DBL_MAX) return 0;
return avg_inter_arrival_;
}
bool RTCDataPath::isActive() {
if (received_nacks_ && rounds_without_packets_ < MAX_ROUNDS_WITHOUT_PKTS)
return true;
return false;
}
void RTCDataPath::roundEnd() {
// reset min_rtt and add it to the history
if (min_rtt != UINT_MAX) {
prev_min_rtt = min_rtt;
} else {
// this may happen if we do not receive any packet
// from this path in the last round. in this case
// we use the measure from the previuos round
min_rtt = prev_min_rtt;
}
if (min_rtt == 0) min_rtt = 1;
RTThistory_.pushBack(min_rtt);
min_rtt = UINT_MAX;
// do the same for min owd
if (min_owd != INT_MAX) {
prev_min_owd = min_owd;
} else {
min_owd = prev_min_owd;
}
if (min_owd != INT_MAX) {
OWDhistory_.pushBack(min_owd);
min_owd = INT_MAX;
// compute queuing delay
queuing_delay = avg_owd - getMinOwd();
} else {
queuing_delay = 0.0;
}
if (!received_packets_)
rounds_without_packets_++;
else
rounds_without_packets_ = 0;
received_packets_ = false;
}
double RTCDataPath::getQueuingDealy() { return queuing_delay; }
uint64_t RTCDataPath::getMinRtt() { return RTThistory_.begin(); }
int64_t RTCDataPath::getMinOwd() { return OWDhistory_.begin(); }
} // end namespace protocol
} // end namespace transport
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