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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
//
// Copyright (c) 2006 Georgia Tech Research Corporation
// (c) 2013 University of Arizona
// (c) 2013 University of California, Los Angeles
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation;
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
// Author: Rajib Bhattacharjea<raj.b@gatech.edu>
// Cheng Yi <yic@email.arizona.edu>
// Alexander Afanasyev <alexander.afanasyev@ucla.edu>
//
// Georgia Tech Network Simulator - Round Trip Time Estimation Class
// George F. Riley. Georgia Tech, Spring 2002
#include "ndn-rtt-mean-deviation.h"
#include "ns3/simulator.h"
#include "ns3/double.h"
#include "ns3/integer.h"
#include "ns3/uinteger.h"
#include "ns3/log.h"
NS_LOG_COMPONENT_DEFINE ("ndn.RttMeanDeviation");
namespace ns3 {
namespace ndn {
//---------------------------------------------------------------------------------
// A modified version of Mean-Deviation Estimator optimized for NDN packet delivery
NS_OBJECT_ENSURE_REGISTERED (RttMeanDeviation);
TypeId
RttMeanDeviation::GetTypeId (void)
{
static TypeId tid = TypeId ("ns3::ndn::RttMeanDeviation")
.SetParent<RttEstimator> ()
.AddConstructor<RttMeanDeviation> ()
.AddAttribute ("Gain",
"Gain used in estimating the RTT (smoothed RTT), must be 0 < Gain < 1",
DoubleValue (0.125),
MakeDoubleAccessor (&RttMeanDeviation::m_gain),
MakeDoubleChecker<double> ())
.AddAttribute ("Gain2",
"Gain2 used in estimating the RTT (variance), must be 0 < Gain2 < 1",
DoubleValue (0.25),
MakeDoubleAccessor (&RttMeanDeviation::m_gain2),
MakeDoubleChecker<double> ())
;
return tid;
}
RttMeanDeviation::RttMeanDeviation() :
m_variance (0)
{
NS_LOG_FUNCTION (this);
}
RttMeanDeviation::RttMeanDeviation (const RttMeanDeviation& c)
: RttEstimator (c), m_gain (c.m_gain), m_gain2 (c.m_gain2), m_variance (c.m_variance)
{
NS_LOG_FUNCTION (this);
}
void RttMeanDeviation::Measurement (Time m)
{
NS_LOG_FUNCTION (this << m);
if (m_nSamples)
{ // Not first
Time err (m - m_currentEstimatedRtt);
double gErr = err.ToDouble (Time::S) * m_gain;
m_currentEstimatedRtt += Time::FromDouble (gErr, Time::S);
Time difference = Abs (err) - m_variance;
NS_LOG_DEBUG ("m_variance += " << Time::FromDouble (difference.ToDouble (Time::S) * m_gain2, Time::S));
m_variance += Time::FromDouble (difference.ToDouble (Time::S) * m_gain2, Time::S);
}
else
{ // First sample
m_currentEstimatedRtt = m; // Set estimate to current
//variance = sample / 2; // And variance to current / 2
// m_variance = m; // try this why????
m_variance = Seconds (m.ToDouble (Time::S) / 2);
NS_LOG_DEBUG ("(first sample) m_variance += " << m);
}
m_nSamples++;
}
Time RttMeanDeviation::RetransmitTimeout ()
{
NS_LOG_FUNCTION (this);
double retval = std::min (m_maxRto.ToDouble (Time::S),
std::max (m_multiplier*m_minRto.ToDouble (Time::S),
m_multiplier*(m_currentEstimatedRtt.ToDouble (Time::S) + 4 * m_variance.ToDouble (Time::S))));
NS_LOG_DEBUG ("RetransmitTimeout: return " << retval);
return Seconds (retval);
}
Ptr<RttEstimator> RttMeanDeviation::Copy () const
{
NS_LOG_FUNCTION (this);
return CopyObject<RttMeanDeviation> (this);
}
void RttMeanDeviation::Reset ()
{
NS_LOG_FUNCTION (this);
// Reset to initial state
m_variance = Seconds (0);
RttEstimator::Reset ();
}
void RttMeanDeviation::Gain (double g)
{
NS_LOG_FUNCTION (this);
NS_ASSERT_MSG( (g > 0) && (g < 1), "RttMeanDeviation: Gain must be less than 1 and greater than 0" );
m_gain = g;
}
Time RttMeanDeviation::AckSeq (SequenceNumber32 ackSeq)
{
NS_LOG_FUNCTION (this << ackSeq);
// An ack has been received, calculate rtt and log this measurement
// Note we use a linear search (O(n)) for this since for the common
// case the ack'ed packet will be at the head of the list
Time m = Seconds (0.0);
if (m_history.size () == 0) return (m); // No pending history, just exit
for (RttHistory_t::iterator i = m_history.begin (); i != m_history.end (); ++i)
{
if (ackSeq == i->seq)
{ // Found it
m = Simulator::Now () - i->time;// Elapsed time
Measurement (m); // Log the measurement
ResetMultiplier (); // Reset multiplier on valid measurement
m_history.erase(i);
break;
}
}
return m;
}
} // namespace ndn
} // namespace ns3