Enable Kathleen Nichols min rtt algorithm with a 1 minute window in

net/quic/quic_sent_packet_manager.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_sent_packet_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "net/quic/congestion_control/pacing_sender.h"
 #include "net/quic/crypto/crypto_protocol.h"
 #include "net/quic/quic_ack_notifier_manager.h"
 #include "net/quic/quic_connection_stats.h"
 #include "net/quic/quic_flags.h"
 #include "net/quic/quic_utils_chromium.h"
 
 using std::make_pair;
 using std::max;
 using std::min;
 
 namespace net {
+
+// The length of the recent min rtt window in seconds. Windowing is disabled for
+// values less than or equal to 0.
+int32 FLAGS_quic_recent_min_rtt_window_s = 60;
+
 namespace {
 static const int kDefaultRetransmissionTimeMs = 500;
 // TCP RFC calls for 1 second RTO however Linux differs from this default and
 // define the minimum RTO to 200ms, we will use the same until we have data to
 // support a higher or lower value.
 static const int kMinRetransmissionTimeMs = 200;
 static const int kMaxRetransmissionTimeMs = 60000;
 static const size_t kMaxRetransmissions = 10;
 
 // Only exponentially back off the handshake timer 5 times due to a timeout.
 static const size_t kMaxHandshakeRetransmissionBackoffs = 5;
 static const size_t kMinHandshakeTimeoutMs = 10;
 
 // Sends up to two tail loss probes before firing an RTO,
 // per draft RFC draft-dukkipati-tcpm-tcp-loss-probe.
 static const size_t kDefaultMaxTailLossProbes = 2;
 static const int64 kMinTailLossProbeTimeoutMs = 10;
 
 // Number of samples before we force a new recent min rtt to be captured.
 static const size_t kNumMinRttSamplesAfterQuiescence = 2;
 
 // Number of unpaced packets to send after quiescence.
 static const size_t kInitialUnpacedBurst = 10;
 
+// Use a 1 minute window for Recent Min RTT with BBR.
+
 bool HasCryptoHandshake(const TransmissionInfo& transmission_info) {
   if (transmission_info.retransmittable_frames == NULL) {
     return false;
   }
   return transmission_info.retransmittable_frames->HasCryptoHandshake() ==
       IS_HANDSHAKE;
 }
 
 }  // namespace
 
@@ skipping 27 matching lines @@
 
 void QuicSentPacketManager::SetFromConfig(const QuicConfig& config) {
   if (config.HasReceivedInitialRoundTripTimeUs() &&
       config.ReceivedInitialRoundTripTimeUs() > 0) {
     rtt_stats_.set_initial_rtt_us(min(kMaxInitialRoundTripTimeUs,
                                       config.ReceivedInitialRoundTripTimeUs()));
   }
   // TODO(ianswett): BBR is currently a server only feature.
   if (config.HasReceivedConnectionOptions() &&
       ContainsQuicTag(config.ReceivedConnectionOptions(), kTBBR)) {
+    if (FLAGS_quic_recent_min_rtt_window_s > 0) {
+      rtt_stats_.set_recent_min_rtt_window(
+          QuicTime::Delta::FromSeconds(FLAGS_quic_recent_min_rtt_window_s));
+    }
     send_algorithm_.reset(
         SendAlgorithmInterface::Create(clock_, &rtt_stats_, kTCPBBR, stats_));
   }
   if (config.congestion_feedback() == kPACE ||
       (config.HasReceivedConnectionOptions() &&
        ContainsQuicTag(config.ReceivedConnectionOptions(), kPACE))) {
     MaybeEnablePacing();
   }
   // TODO(ianswett): Remove the "HasReceivedLossDetection" branch once
   // the ConnectionOptions code is live everywhere.
@@ skipping 709 matching lines @@
 
   // Set up a pacing sender with a 5 millisecond alarm granularity.
   using_pacing_ = true;
   send_algorithm_.reset(
       new PacingSender(send_algorithm_.release(),
                        QuicTime::Delta::FromMilliseconds(5),
                        kInitialUnpacedBurst));
 }
 
 }  // namespace net