apps/ndn-consumer.cc - ndnSIM - Gitiles

 /* -*-  Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
 /*
  * Copyright (c) 2011 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: Ilya Moiseenko <iliamo@cs.ucla.edu>
  */

 #include "ndn-consumer.h"
 #include "ns3/ptr.h"
 #include "ns3/log.h"
 #include "ns3/simulator.h"
 #include "ns3/packet.h"
 #include "ns3/callback.h"
 #include "ns3/string.h"
 #include "ns3/boolean.h"
 #include "ns3/uinteger.h"
 #include "ns3/double.h"

 #include "ns3/ndn.h"
 #include "ns3/ndn-app-face.h"
 #include "ns3/ndn-interest-header.h"
 #include "ns3/ndn-content-object-header.h"
 // #include "ns3/weights-path-stretch-tag.h"

 #include <boost/ref.hpp>
 #include <boost/lexical_cast.hpp>
 #include <boost/lambda/lambda.hpp>
 #include <boost/lambda/bind.hpp>

 #include "ns3/names.h"

 namespace ll = boost::lambda;

 NS_LOG_COMPONENT_DEFINE ("ndn.Consumer");

 namespace ns3 {
 namespace ndn {

 NS_OBJECT_ENSURE_REGISTERED (Consumer);

 TypeId
 Consumer::GetTypeId (void)
 {
   static TypeId tid = TypeId ("ns3::ndn::Consumer")
     .SetGroupName ("Ndn")
     .SetParent<App> ()
     .AddAttribute ("StartSeq", "Initial sequence number",
                    IntegerValue (0),
                    MakeIntegerAccessor(&Consumer::m_seq),
                    MakeIntegerChecker<int32_t>())

     .AddAttribute ("Prefix","Name of the Interest",
                    StringValue ("/"),
                    MakeNameComponentsAccessor (&Consumer::m_interestName),
                    MakeNameComponentsChecker ())
     .AddAttribute ("LifeTime", "LifeTime for interest packet",
                    StringValue ("2s"),
                    MakeTimeAccessor (&Consumer::m_interestLifeTime),
                    MakeTimeChecker ())
     .AddAttribute ("MinSuffixComponents", "MinSuffixComponents",
                    IntegerValue(-1),
                    MakeIntegerAccessor(&Consumer::m_minSuffixComponents),
                    MakeIntegerChecker<int32_t>())
     .AddAttribute ("MaxSuffixComponents", "MaxSuffixComponents",
                    IntegerValue(-1),
                    MakeIntegerAccessor(&Consumer::m_maxSuffixComponents),
                    MakeIntegerChecker<int32_t>())
     .AddAttribute ("ChildSelector", "ChildSelector",
                    BooleanValue(false),
                    MakeBooleanAccessor(&Consumer::m_childSelector),
                    MakeBooleanChecker())
     .AddAttribute ("Exclude", "only simple name matching is supported (use NameComponents)",
                    NameComponentsValue (),
                    MakeNameComponentsAccessor (&Consumer::m_exclude),
                    MakeNameComponentsChecker ())

     .AddAttribute ("RetxTimer",
                    "Timeout defining how frequent retransmission timeouts should be checked",
                    StringValue ("50ms"),
                    MakeTimeAccessor (&Consumer::GetRetxTimer, &Consumer::SetRetxTimer),
                    MakeTimeChecker ())

     .AddTraceSource ("PathWeightsTrace", "PathWeightsTrace",
                     MakeTraceSourceAccessor (&Consumer::m_pathWeightsTrace))
     ;

   return tid;
 }

 Consumer::Consumer ()
   : m_rand (0, std::numeric_limits<uint32_t>::max ())
   , m_seq (0)
   , m_seqMax (0) // don't request anything
 {
   NS_LOG_FUNCTION_NOARGS ();

   m_rtt = CreateObject<RttMeanDeviation> ();
 }

 void
 Consumer::SetRetxTimer (Time retxTimer)
 {
   m_retxTimer = retxTimer;
   if (m_retxEvent.IsRunning ())
     m_retxEvent.Cancel (); // cancel any scheduled cleanup events

   // schedule even with new timeout
   m_retxEvent = Simulator::Schedule (m_retxTimer,
                                      &Consumer::CheckRetxTimeout, this);
 }

 Time
 Consumer::GetRetxTimer () const
 {
   return m_retxTimer;
 }

 void
 Consumer::CheckRetxTimeout ()
 {
   Time now = Simulator::Now ();

   Time rto = m_rtt->RetransmitTimeout ();

   while (!m_seqTimeouts.empty ())
     {
       SeqTimeoutsContainer::index<i_timestamp>::type::iterator entry =
         m_seqTimeouts.get<i_timestamp> ().begin ();
       if (entry->time + rto <= now) // timeout expired?
         {
           uint32_t seqNo = entry->seq;
           m_seqTimeouts.get<i_timestamp> ().erase (entry);
           OnTimeout (seqNo);
         }
       else
         break; // nothing else to do. All later packets need not be retransmitted
     }

   m_retxEvent = Simulator::Schedule (m_retxTimer,
                                      &Consumer::CheckRetxTimeout, this);
 }

 // Application Methods
 void
 Consumer::StartApplication () // Called at time specified by Start
 {
   NS_LOG_FUNCTION_NOARGS ();

   // do base stuff
   App::StartApplication ();

   ScheduleNextPacket ();
 }

 void
 Consumer::StopApplication () // Called at time specified by Stop
 {
   NS_LOG_FUNCTION_NOARGS ();

   // cancel periodic packet generation
   Simulator::Cancel (m_sendEvent);

   // cleanup base stuff
   App::StopApplication ();
 }

 void
 Consumer::SendPacket ()
 {
   if (!m_active) return;

   NS_LOG_FUNCTION_NOARGS ();

   uint32_t seq=std::numeric_limits<uint32_t>::max (); //invalid

   // std::cout << Simulator::Now ().ToDouble (Time::S) << "s max -> " << m_seqMax << "\n";

   while (m_retxSeqs.size ())
     {
       seq = *m_retxSeqs.begin ();
       m_retxSeqs.erase (m_retxSeqs.begin ());

       // NS_ASSERT (m_seqLifetimes.find (seq) != m_seqLifetimes.end ());
       // if (m_seqLifetimes.find (seq)->time <= Simulator::Now ())
       //   {

       //     NS_LOG_DEBUG ("Expire " << seq);
       //     m_seqLifetimes.erase (seq); // lifetime expired. Trying to find another unexpired sequence number
       //     continue;
       //   }
       break;
     }

   if (seq == std::numeric_limits<uint32_t>::max ())
     {
       if (m_seqMax != std::numeric_limits<uint32_t>::max ())
         {
           if (m_seq >= m_seqMax)
             {
               return; // we are totally done
             }
         }

       seq = m_seq++;
     }

   // std::cout << Simulator::Now ().ToDouble (Time::S) << "s -> " << seq << "\n";

   //
   Ptr<NameComponents> nameWithSequence = Create<NameComponents> (m_interestName);
   (*nameWithSequence) (seq);
   //

   InterestHeader interestHeader;
   interestHeader.SetNonce               (m_rand.GetValue ());
   interestHeader.SetName                (nameWithSequence);
   interestHeader.SetInterestLifetime    (m_interestLifeTime);
   interestHeader.SetChildSelector       (m_childSelector);
   if (m_exclude.size ()>0)
     {
       interestHeader.SetExclude (Create<NameComponents> (m_exclude));
     }
   interestHeader.SetMaxSuffixComponents (m_maxSuffixComponents);
   interestHeader.SetMinSuffixComponents (m_minSuffixComponents);

   // NS_LOG_INFO ("Requesting Interest: \n" << interestHeader);
   NS_LOG_INFO ("> Interest for " << seq);

   Ptr<Packet> packet = Create<Packet> ();
   packet->AddHeader (interestHeader);
   NS_LOG_DEBUG ("Interest packet size: " << packet->GetSize ());

   m_protocolHandler (packet);

   NS_LOG_DEBUG ("Trying to add " << seq << " with " << Simulator::Now () << ". already " << m_seqTimeouts.size () << " items");

   m_seqTimeouts.insert (SeqTimeout (seq, Simulator::Now ()));
   m_seqLifetimes.insert (SeqTimeout (seq, Simulator::Now () + m_interestLifeTime)); // only one insert will work. if entry exists, nothing will happen... nothing should happen
   m_transmittedInterests (&interestHeader, this, m_face);

   m_rtt->SentSeq (SequenceNumber32 (seq), 1);
   ScheduleNextPacket ();
 }

 ///////////////////////////////////////////////////
 //          Process incoming packets             //
 ///////////////////////////////////////////////////


 void
 Consumer::OnContentObject (const Ptr<const ContentObjectHeader> &contentObject,
                                Ptr<Packet> payload)
 {
   if (!m_active) return;

   App::OnContentObject (contentObject, payload); // tracing inside

   NS_LOG_FUNCTION (this << contentObject << payload);

   // NS_LOG_INFO ("Received content object: " << boost::cref(*contentObject));

   uint32_t seq = boost::lexical_cast<uint32_t> (contentObject->GetName ().GetComponents ().back ());
   NS_LOG_INFO ("< DATA for " << seq);

   // SeqTimeoutsContainer::iterator entry = m_seqTimeouts.find (seq);

   //  NS_ASSERT_MSG (entry != m_seqTimeouts.end (),
   //             "Comment out this assert, if it causes problems");

   // if (entry != m_seqTimeouts.end ())
   //   m_seqTimeouts.erase (entry);

   m_seqLifetimes.erase (seq);
   m_seqTimeouts.erase (seq);
   m_retxSeqs.erase (seq);

   m_rtt->AckSeq (SequenceNumber32 (seq));

   // Ptr<const WeightsPathStretchTag> tag = payload->RemovePacketTag<WeightsPathStretchTag> ();
   // if (tag != 0)
   //   {
   //     // Notify trace about path weights vector (e.g., for path-stretch calculation)
   //     m_pathWeightsTrace (GetNode (), tag->GetSourceNode (), seq, tag->GetTotalWeight ());
   //     // if (Names::FindName (GetNode ()) == "36")// || Names::FindName (GetNode ()) == "40"|| Names::FindName (GetNode ()) == "5")
   //     //   std::cout << Simulator::Now () << "\t" << boost::cref(*tag) << " = " << tag->GetTotalWeight () << "\n";
   //   }
 }

 void
 Consumer::OnNack (const Ptr<const InterestHeader> &interest, Ptr<Packet> origPacket)
 {
   if (!m_active) return;

   App::OnNack (interest, origPacket); // tracing inside

   NS_LOG_DEBUG ("Nack type: " << interest->GetNack ());

   NS_LOG_FUNCTION (this << interest);

   // NS_LOG_INFO ("Received NACK: " << boost::cref(*interest));
   uint32_t seq = boost::lexical_cast<uint32_t> (interest->GetName ().GetComponents ().back ());
   NS_LOG_INFO ("< NACK for " << seq);
   // std::cout << Simulator::Now ().ToDouble (Time::S) << "s -> " << "NACK for " << seq << "\n";

   // put in the queue of interests to be retransmitted
   NS_LOG_INFO ("Before: " << m_retxSeqs.size ());
   m_retxSeqs.insert (seq);
   NS_LOG_INFO ("After: " << m_retxSeqs.size ());

   // m_rtt->IncreaseMultiplier ();             // Double the next RTO ??
   ScheduleNextPacket ();
 }

 void
 Consumer::OnTimeout (uint32_t sequenceNumber)
 {
   // std::cout << Simulator::Now () << ", TO: " << sequenceNumber << ", current RTO: " << m_rtt->RetransmitTimeout ().ToDouble (Time::S) << "s\n";

   // m_rtt->IncreaseMultiplier ();             // Double the next RTO
   m_rtt->SentSeq (SequenceNumber32 (sequenceNumber), 1); // make sure to disable RTT calculation for this sample
   m_retxSeqs.insert (sequenceNumber);
   ScheduleNextPacket ();
 }

 } // namespace ndn
 } // namespace ns3
	/* -- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -- */
	/*
	* Copyright (c) 2011 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: Ilya Moiseenko <iliamo@cs.ucla.edu>
	*/

	#include "ndn-consumer.h"
	#include "ns3/ptr.h"
	#include "ns3/log.h"
	#include "ns3/simulator.h"
	#include "ns3/packet.h"
	#include "ns3/callback.h"
	#include "ns3/string.h"
	#include "ns3/boolean.h"
	#include "ns3/uinteger.h"
	#include "ns3/double.h"

	#include "ns3/ndn.h"
	#include "ns3/ndn-app-face.h"
	#include "ns3/ndn-interest-header.h"
	#include "ns3/ndn-content-object-header.h"
	// #include "ns3/weights-path-stretch-tag.h"

	#include <boost/ref.hpp>
	#include <boost/lexical_cast.hpp>
	#include <boost/lambda/lambda.hpp>
	#include <boost/lambda/bind.hpp>

	#include "ns3/names.h"

	namespace ll = boost::lambda;

	NS_LOG_COMPONENT_DEFINE ("ndn.Consumer");

	namespace ns3 {
	namespace ndn {

	NS_OBJECT_ENSURE_REGISTERED (Consumer);

	TypeId
	Consumer::GetTypeId (void)
	{
	static TypeId tid = TypeId ("ns3::ndn::Consumer")
	.SetGroupName ("Ndn")
	.SetParent<App> ()
	.AddAttribute ("StartSeq", "Initial sequence number",
	IntegerValue (0),
	MakeIntegerAccessor(&Consumer::m_seq),
	MakeIntegerChecker<int32_t>())

	.AddAttribute ("Prefix","Name of the Interest",
	StringValue ("/"),
	MakeNameComponentsAccessor (&Consumer::m_interestName),
	MakeNameComponentsChecker ())
	.AddAttribute ("LifeTime", "LifeTime for interest packet",
	StringValue ("2s"),
	MakeTimeAccessor (&Consumer::m_interestLifeTime),
	MakeTimeChecker ())
	.AddAttribute ("MinSuffixComponents", "MinSuffixComponents",
	IntegerValue(-1),
	MakeIntegerAccessor(&Consumer::m_minSuffixComponents),
	MakeIntegerChecker<int32_t>())
	.AddAttribute ("MaxSuffixComponents", "MaxSuffixComponents",
	IntegerValue(-1),
	MakeIntegerAccessor(&Consumer::m_maxSuffixComponents),
	MakeIntegerChecker<int32_t>())
	.AddAttribute ("ChildSelector", "ChildSelector",
	BooleanValue(false),
	MakeBooleanAccessor(&Consumer::m_childSelector),
	MakeBooleanChecker())
	.AddAttribute ("Exclude", "only simple name matching is supported (use NameComponents)",
	NameComponentsValue (),
	MakeNameComponentsAccessor (&Consumer::m_exclude),
	MakeNameComponentsChecker ())

	.AddAttribute ("RetxTimer",
	"Timeout defining how frequent retransmission timeouts should be checked",
	StringValue ("50ms"),
	MakeTimeAccessor (&Consumer::GetRetxTimer, &Consumer::SetRetxTimer),
	MakeTimeChecker ())

	.AddTraceSource ("PathWeightsTrace", "PathWeightsTrace",
	MakeTraceSourceAccessor (&Consumer::m_pathWeightsTrace))
	;

	return tid;
	}

	Consumer::Consumer ()
	: m_rand (0, std::numeric_limits<uint32_t>::max ())
	, m_seq (0)
	, m_seqMax (0) // don't request anything
	{
	NS_LOG_FUNCTION_NOARGS ();

	m_rtt = CreateObject<RttMeanDeviation> ();
	}

	void
	Consumer::SetRetxTimer (Time retxTimer)
	{
	m_retxTimer = retxTimer;
	if (m_retxEvent.IsRunning ())
	m_retxEvent.Cancel (); // cancel any scheduled cleanup events

	// schedule even with new timeout
	m_retxEvent = Simulator::Schedule (m_retxTimer,
	&Consumer::CheckRetxTimeout, this);
	}

	Time
	Consumer::GetRetxTimer () const
	{
	return m_retxTimer;
	}

	void
	Consumer::CheckRetxTimeout ()
	{
	Time now = Simulator::Now ();

	Time rto = m_rtt->RetransmitTimeout ();

	while (!m_seqTimeouts.empty ())
	{
	SeqTimeoutsContainer::index<i_timestamp>::type::iterator entry =
	m_seqTimeouts.get<i_timestamp> ().begin ();
	if (entry->time + rto <= now) // timeout expired?
	{
	uint32_t seqNo = entry->seq;
	m_seqTimeouts.get<i_timestamp> ().erase (entry);
	OnTimeout (seqNo);
	}
	else
	break; // nothing else to do. All later packets need not be retransmitted
	}

	m_retxEvent = Simulator::Schedule (m_retxTimer,
	&Consumer::CheckRetxTimeout, this);
	}

	// Application Methods
	void
	Consumer::StartApplication () // Called at time specified by Start
	{
	NS_LOG_FUNCTION_NOARGS ();

	// do base stuff
	App::StartApplication ();

	ScheduleNextPacket ();
	}

	void
	Consumer::StopApplication () // Called at time specified by Stop
	{
	NS_LOG_FUNCTION_NOARGS ();

	// cancel periodic packet generation
	Simulator::Cancel (m_sendEvent);

	// cleanup base stuff
	App::StopApplication ();
	}

	void
	Consumer::SendPacket ()
	{
	if (!m_active) return;

	NS_LOG_FUNCTION_NOARGS ();

	uint32_t seq=std::numeric_limits<uint32_t>::max (); //invalid

	// std::cout << Simulator::Now ().ToDouble (Time::S) << "s max -> " << m_seqMax << "\n";

	while (m_retxSeqs.size ())
	{
	seq = *m_retxSeqs.begin ();
	m_retxSeqs.erase (m_retxSeqs.begin ());

	// NS_ASSERT (m_seqLifetimes.find (seq) != m_seqLifetimes.end ());
	// if (m_seqLifetimes.find (seq)->time <= Simulator::Now ())
	// {

	// NS_LOG_DEBUG ("Expire " << seq);
	// m_seqLifetimes.erase (seq); // lifetime expired. Trying to find another unexpired sequence number
	// continue;
	// }
	break;
	}

	if (seq == std::numeric_limits<uint32_t>::max ())
	{
	if (m_seqMax != std::numeric_limits<uint32_t>::max ())
	{
	if (m_seq >= m_seqMax)
	{
	return; // we are totally done
	}
	}

	seq = m_seq++;
	}

	// std::cout << Simulator::Now ().ToDouble (Time::S) << "s -> " << seq << "\n";

	//
	Ptr<NameComponents> nameWithSequence = Create<NameComponents> (m_interestName);
	(*nameWithSequence) (seq);
	//

	InterestHeader interestHeader;
	interestHeader.SetNonce (m_rand.GetValue ());
	interestHeader.SetName (nameWithSequence);
	interestHeader.SetInterestLifetime (m_interestLifeTime);
	interestHeader.SetChildSelector (m_childSelector);
	if (m_exclude.size ()>0)
	{
	interestHeader.SetExclude (Create<NameComponents> (m_exclude));
	}
	interestHeader.SetMaxSuffixComponents (m_maxSuffixComponents);
	interestHeader.SetMinSuffixComponents (m_minSuffixComponents);

	// NS_LOG_INFO ("Requesting Interest: \n" << interestHeader);
	NS_LOG_INFO ("> Interest for " << seq);

	Ptr<Packet> packet = Create<Packet> ();
	packet->AddHeader (interestHeader);
	NS_LOG_DEBUG ("Interest packet size: " << packet->GetSize ());

	m_protocolHandler (packet);

	NS_LOG_DEBUG ("Trying to add " << seq << " with " << Simulator::Now () << ". already " << m_seqTimeouts.size () << " items");

	m_seqTimeouts.insert (SeqTimeout (seq, Simulator::Now ()));
	m_seqLifetimes.insert (SeqTimeout (seq, Simulator::Now () + m_interestLifeTime)); // only one insert will work. if entry exists, nothing will happen... nothing should happen
	m_transmittedInterests (&interestHeader, this, m_face);

	m_rtt->SentSeq (SequenceNumber32 (seq), 1);
	ScheduleNextPacket ();
	}

	///////////////////////////////////////////////////
	// Process incoming packets //
	///////////////////////////////////////////////////


	void
	Consumer::OnContentObject (const Ptr<const ContentObjectHeader> &contentObject,
	Ptr<Packet> payload)
	{
	if (!m_active) return;

	App::OnContentObject (contentObject, payload); // tracing inside

	NS_LOG_FUNCTION (this << contentObject << payload);

	// NS_LOG_INFO ("Received content object: " << boost::cref(*contentObject));

	uint32_t seq = boost::lexical_cast<uint32_t> (contentObject->GetName ().GetComponents ().back ());
	NS_LOG_INFO ("< DATA for " << seq);

	// SeqTimeoutsContainer::iterator entry = m_seqTimeouts.find (seq);

	// NS_ASSERT_MSG (entry != m_seqTimeouts.end (),
	// "Comment out this assert, if it causes problems");

	// if (entry != m_seqTimeouts.end ())
	// m_seqTimeouts.erase (entry);

	m_seqLifetimes.erase (seq);
	m_seqTimeouts.erase (seq);
	m_retxSeqs.erase (seq);

	m_rtt->AckSeq (SequenceNumber32 (seq));

	// Ptr<const WeightsPathStretchTag> tag = payload->RemovePacketTag<WeightsPathStretchTag> ();
	// if (tag != 0)
	// {
	// // Notify trace about path weights vector (e.g., for path-stretch calculation)
	// m_pathWeightsTrace (GetNode (), tag->GetSourceNode (), seq, tag->GetTotalWeight ());
	// // if (Names::FindName (GetNode ()) == "36")// \|\| Names::FindName (GetNode ()) == "40"\|\| Names::FindName (GetNode ()) == "5")
	// // std::cout << Simulator::Now () << "\t" << boost::cref(*tag) << " = " << tag->GetTotalWeight () << "\n";
	// }
	}

	void
	Consumer::OnNack (const Ptr<const InterestHeader> &interest, Ptr<Packet> origPacket)
	{
	if (!m_active) return;

	App::OnNack (interest, origPacket); // tracing inside

	NS_LOG_DEBUG ("Nack type: " << interest->GetNack ());

	NS_LOG_FUNCTION (this << interest);

	// NS_LOG_INFO ("Received NACK: " << boost::cref(*interest));
	uint32_t seq = boost::lexical_cast<uint32_t> (interest->GetName ().GetComponents ().back ());
	NS_LOG_INFO ("< NACK for " << seq);
	// std::cout << Simulator::Now ().ToDouble (Time::S) << "s -> " << "NACK for " << seq << "\n";

	// put in the queue of interests to be retransmitted
	NS_LOG_INFO ("Before: " << m_retxSeqs.size ());
	m_retxSeqs.insert (seq);
	NS_LOG_INFO ("After: " << m_retxSeqs.size ());

	// m_rtt->IncreaseMultiplier (); // Double the next RTO ??
	ScheduleNextPacket ();
	}

	void
	Consumer::OnTimeout (uint32_t sequenceNumber)
	{
	// std::cout << Simulator::Now () << ", TO: " << sequenceNumber << ", current RTO: " << m_rtt->RetransmitTimeout ().ToDouble (Time::S) << "s\n";

	// m_rtt->IncreaseMultiplier (); // Double the next RTO
	m_rtt->SentSeq (SequenceNumber32 (sequenceNumber), 1); // make sure to disable RTT calculation for this sample
	m_retxSeqs.insert (sequenceNumber);
	ScheduleNextPacket ();
	}

	} // namespace ndn
	} // namespace ns3