Issue #25 Replacing usage of TCP RTT estimator with a customized version
In the current commit, RTT estimator does not implement Karn's algorithm
and takes into account all RTT samples, including ambiguous samples from
retransmitted Interests.
diff --git a/utils/ndn-rtt-mean-deviation.cc b/utils/ndn-rtt-mean-deviation.cc
new file mode 100644
index 0000000..8675479
--- /dev/null
+++ b/utils/ndn-rtt-mean-deviation.cc
@@ -0,0 +1,160 @@
+/* -*- 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
+