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      1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 // Based on the inter arrival time of the received packets relative to the time
      6 // those packets where sent we can estimate the max capacity of the channel.
      7 // We can only use packet pair that are sent out faster than the acctual
      8 // channel capacity.
      9 #ifndef NET_QUIC_CONGESTION_CONTROL_CHANNEL_ESTIMATOR_H_
     10 #define NET_QUIC_CONGESTION_CONTROL_CHANNEL_ESTIMATOR_H_
     11 
     12 #include <list>
     13 #include <map>
     14 
     15 #include "base/basictypes.h"
     16 #include "net/base/net_export.h"
     17 #include "net/quic/congestion_control/quic_max_sized_map.h"
     18 #include "net/quic/quic_bandwidth.h"
     19 #include "net/quic/quic_protocol.h"
     20 #include "net/quic/quic_time.h"
     21 
     22 namespace net {
     23 
     24 enum ChannelEstimateState {
     25   kChannelEstimateUnknown = 0,
     26   kChannelEstimateUncertain = 1,
     27   kChannelEstimateGood = 2
     28 };
     29 
     30 class NET_EXPORT_PRIVATE ChannelEstimator {
     31  public:
     32   ChannelEstimator();
     33   ~ChannelEstimator();
     34 
     35   // This method should be called each time we acquire a receive time for a
     36   // packet we previously sent.  It calculates deltas between consecutive
     37   // receive times, and may use that to update the channel bandwidth estimate.
     38   void OnAcknowledgedPacket(QuicPacketSequenceNumber sequence_number,
     39                             QuicByteCount packet_size,
     40                             QuicTime send_time,
     41                             QuicTime receive_time);
     42 
     43   // Get the current estimated state and channel capacity.
     44   // Note: estimate will not be valid when kChannelEstimateUnknown is returned.
     45   ChannelEstimateState GetChannelEstimate(QuicBandwidth* estimate) const;
     46 
     47  private:
     48   void UpdateFilter(QuicTime::Delta received_delta, QuicByteCount size_delta,
     49                     QuicPacketSequenceNumber sequence_number);
     50 
     51   QuicPacketSequenceNumber last_sequence_number_;
     52   QuicTime last_send_time_;
     53   QuicTime last_receive_time_;
     54   QuicMaxSizedMap<QuicBandwidth, QuicPacketSequenceNumber>
     55       sorted_bitrate_estimates_;
     56 
     57   DISALLOW_COPY_AND_ASSIGN(ChannelEstimator);
     58 };
     59 
     60 }  // namespace net
     61 #endif  // NET_QUIC_CONGESTION_CONTROL_CHANNEL_ESTIMATOR_H_
     62