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/*
* Copyright (c) 2021 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/rtc_consts.h>
#include <protocols/rtc/rtc_rc_queue.h>
#include <algorithm>
namespace transport {
namespace protocol {
namespace rtc {
RTCRateControlQueue::RTCRateControlQueue()
: rounds_since_last_drop_(0),
rounds_without_congestion_(0),
last_queue_(0) {}
RTCRateControlQueue::~RTCRateControlQueue() {}
void RTCRateControlQueue::onNewRound(double round_len) {
if (!rc_on_) return;
double received_rate = protocol_state_->getReceivedRate();
double target_rate =
protocol_state_->getProducerRate() * PRODUCTION_RATE_FRACTION;
double rtt = (double)protocol_state_->getMinRTT() / MILLI_IN_A_SEC;
double packet_size = protocol_state_->getAveragePacketSize();
double queue = protocol_state_->getQueuing();
if (rtt == 0.0) return; // no info from the producer
CongestionState prev_congestion_state = congestion_state_;
if (prev_congestion_state == CongestionState::Normal &&
received_rate >= target_rate) {
// if the queue is high in this case we are most likelly fighting with
// a TCP flow and there is enough bandwidth to match the producer rate
congestion_state_ = CongestionState::Normal;
} else if (queue > MAX_QUEUING_DELAY || last_queue_ == queue) {
// here we detect congestion. in the case that last_queue == queue
// the consumer didn't receive any packet from the producer so we
// consider this case as congestion
// TODO: wath happen in case of high loss rate?
congestion_state_ = CongestionState::Congested;
} else {
// nothing bad is happening
congestion_state_ = CongestionState::Normal;
}
last_queue_ = queue;
if (congestion_state_ == CongestionState::Congested) {
if (prev_congestion_state == CongestionState::Normal) {
// init the congetion window using the received rate
congestion_win_ = (uint32_t)ceil(received_rate * rtt / packet_size);
rounds_since_last_drop_ = ROUNDS_BEFORE_TAKE_ACTION + 1;
}
if (rounds_since_last_drop_ >= ROUNDS_BEFORE_TAKE_ACTION) {
uint32_t win = congestion_win_ * WIN_DECREASE_FACTOR;
congestion_win_ = std::max(win, WIN_MIN);
rounds_since_last_drop_ = 0;
return;
}
rounds_since_last_drop_++;
}
if (congestion_state_ == CongestionState::Normal) {
if (prev_congestion_state == CongestionState::Congested) {
rounds_without_congestion_ = 0;
}
rounds_without_congestion_++;
if (rounds_without_congestion_ < ROUNDS_BEFORE_TAKE_ACTION) return;
congestion_win_ = congestion_win_ * WIN_INCREASE_FACTOR;
congestion_win_ = std::min(congestion_win_, INITIAL_WIN_MAX);
}
}
void RTCRateControlQueue::onDataPacketReceived(
const core::ContentObject &content_object, bool compute_stats) {
// nothing to do
return;
}
} // end namespace rtc
} // end namespace protocol
} // end namespace transport
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