1 files changed, 106 insertions, 0 deletions
diff --git a/libtransport/src/protocols/rtc/rtc_rc_queue.cc b/libtransport/src/protocols/rtc/rtc_rc_queue.cc
new file mode 100644
index 000000000..a1c89e329
--- /dev/null
+++ b/libtransport/src/protocols/rtc/rtc_rc_queue.cc
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2017-2021 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_->getRTT() / 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) {
+  // nothing to do
+  return;
+}
+
+}  // end namespace rtc
+
+}  // end namespace protocol
+
+}  // end namespace transport