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// Copyright (c) 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/congestion_control/available_channel_estimator.h"
static const int kNumberOfSamples = 9;
namespace net {
AvailableChannelEstimator::AvailableChannelEstimator(
QuicPacketSequenceNumber sequence_number,
QuicTime first_send_time,
QuicTime first_receive_time)
: first_sequence_number_(sequence_number),
first_send_time_(first_send_time),
first_receive_time_(first_receive_time),
last_incorporated_sequence_number_(sequence_number),
last_time_sent_(QuicTime::Zero()),
last_receive_time_(QuicTime::Zero()),
number_of_sequence_numbers_(0),
received_bytes_(0) {
}
void AvailableChannelEstimator::OnIncomingFeedback(
QuicPacketSequenceNumber sequence_number,
QuicByteCount packet_size,
QuicTime sent_time,
QuicTime receive_time) {
if (sequence_number <= first_sequence_number_) {
// Ignore pre-probe feedback.
return;
}
if (sequence_number <= last_incorporated_sequence_number_) {
// Ignore old feedback; will remove duplicates.
return;
}
// Remember the highest received sequence number.
last_incorporated_sequence_number_ = sequence_number;
if (number_of_sequence_numbers_ < kNumberOfSamples) {
// We don't care how many sequence numbers we have after we pass
// kNumberOfSamples.
number_of_sequence_numbers_++;
}
last_receive_time_ = receive_time;
last_time_sent_ = sent_time;
received_bytes_ += packet_size;
// TODO(pwestin): the variance here should give us information about accuracy.
}
AvailableChannelEstimateState
AvailableChannelEstimator::GetAvailableChannelEstimate(
QuicBandwidth* bandwidth) const {
if (number_of_sequence_numbers_ < 2) {
return kAvailableChannelEstimateUnknown;
}
QuicTime::Delta send_delta = last_time_sent_.Subtract(first_send_time_);
QuicTime::Delta receive_delta =
last_receive_time_.Subtract(first_receive_time_);
// TODO(pwestin): room for improvement here. Keeping it simple for now.
*bandwidth = QuicBandwidth::FromBytesAndTimeDelta(received_bytes_,
receive_delta);
QuicTime::Delta diff = receive_delta.Subtract(send_delta);
QuicTime::Delta ten_percent_of_send_time =
QuicTime::Delta::FromMicroseconds(send_delta.ToMicroseconds() / 10);
if (diff < ten_percent_of_send_time) {
return kAvailableChannelEstimateSenderLimited;
}
if (number_of_sequence_numbers_ < kNumberOfSamples) {
return kAvailableChannelEstimateUncertain;
}
return kAvailableChannelEstimateGood;
}
} // namespace net
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