1 files changed, 74 insertions, 0 deletions
diff --git a/libtransport/src/protocols/rtc/rtc_rc_congestion_detection.cc b/libtransport/src/protocols/rtc/rtc_rc_congestion_detection.cc
new file mode 100644
index 000000000..6cd3094b5
--- /dev/null
+++ b/libtransport/src/protocols/rtc/rtc_rc_congestion_detection.cc
@@ -0,0 +1,74 @@
+/*
+ * 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_congestion_detection.h>
+
+#include <algorithm>
+
+namespace transport {
+
+namespace protocol {
+
+namespace rtc {
+
+RTCRateControlCongestionDetection::RTCRateControlCongestionDetection()
+    : rounds_without_congestion_(4), last_queue_(0) {}  // must be > 3
+
+RTCRateControlCongestionDetection::~RTCRateControlCongestionDetection() {}
+
+void RTCRateControlCongestionDetection::onNewRound(double round_len) {
+  if (!rc_on_) return;
+
+  double rtt = (double)protocol_state_->getMinRTT() / MILLI_IN_A_SEC;
+  double queue = protocol_state_->getQueuing();
+
+  if (rtt == 0.0) return;  // no info from the producer
+
+  if (last_queue_ == queue) {
+    // if last_queue == queue the consumer didn't receive any
+    // packet from the producer. we do not change the current congestion state.
+    // we just increase the counter of rounds whithout congestion if needed
+    // (in case of congestion the counter is already set to 0)
+    if (congestion_state_ == CongestionState::Normal)
+      rounds_without_congestion_++;
+  } else {
+    if (queue > MAX_QUEUING_DELAY) {
+      // here we detect congestion.
+      congestion_state_ = CongestionState::Congested;
+      rounds_without_congestion_ = 0;
+    } else {
+      // wait 3 rounds before switch back to no congestion
+      if (rounds_without_congestion_ > 3) {
+        // nothing bad is happening
+        congestion_state_ = CongestionState::Normal;
+      }
+      rounds_without_congestion_++;
+    }
+    last_queue_ = queue;
+  }
+}
+
+void RTCRateControlCongestionDetection::onDataPacketReceived(
+    const core::ContentObject &content_object, bool compute_stats) {
+  // nothing to do
+  return;
+}
+
+}  // end namespace rtc
+
+}  // end namespace protocol
+
+}  // end namespace transport