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In ~ns/tcp.h, three classes are derived from the base class class TimerHandler:class RtxTimer : public TimerHandler {public:RtxTimer(TcpAgent *a) : TimerHandler() { a_ = a; }protected:virtual void expire(Event *e);TcpAgent *a_;};class DelSndTimer : public TimerHandler {public:DelSndTimer(TcpAgent *a) : TimerHandler() { a_ = a; }protected:virtual void expire(Event *e);TcpAgent *a_;};class BurstSndTimer : public TimerHandler {public:BurstSndTimer(TcpAgent *a) : TimerHandler() { a_ = a; }protected:virtual void expire(Event *e);TcpAgent *a_;};In the constructor for TcpAgent in tcp.cc, each of these timers is initialized with the this pointer, which is assigned tothe pointer a_.TcpAgent::TcpAgent() : Agent(PT_TCP), rtt_active_(0), rtt_seq_(-1),...rtx_timer_(this), delsnd_timer_(this), burstsnd_timer_(this){...}In the following, we will focus only on the retransmission timer. Various helper methods may be defined to schedule timerevents; e.g.,/** Set retransmit timer using current rtt estimate. By calling resched()* it does not matter whether the timer was already running.*/void TcpAgent::set_rtx_timer(){rtx_timer_.resched(rtt_timeout());}/** Set new retransmission timer if not all outstanding* data has been acked. Otherwise, if a timer is still113
* outstanding, cancel it.*/void TcpAgent::newtimer(Packet* pkt){hdr_tcp *tcph = (hdr_tcp*)pkt->access(off_tcp_);if (t_seqno_ > tcph->seqno())set_rtx_timer();else if (rtx_timer_.status() == TIMER_PENDING)rtx_timer_.cancel();}In the above code, the set_rtx_timer() method reschedules the retransmission timer by calling rtx_timer_.resched().Note that if it is unclear whether or not the timer is already running, calling resched() eliminates the need to explicitly cancelthe timer. In the second function, examples are given of the use of the status() and cancel(void) methods.Finally, the expire(void) method for class RtxTimer must be defined. In this case, expire(void) calls the timeout(void)method for TcpAgent. This is possible because timeout() is a public member function; if it were not, then RtxTimerwould have had to have been declared a friend class of TcpAgent.void TcpAgent::timeout(int tno){/* retransmit timer */if (tno == TCP_TIMER_RTX) {if (highest_ack_ == maxseq_ && !slow_start_restart_) {/** TCP option:* If no outstanding data, then don’t do anything.*/return;};recover_ = maxseq_;recover_cause_ = 2;closecwnd(0);reset_rtx_timer(0,1);send_much(0, TCP_REASON_TIMEOUT, maxburst_);} else {/** delayed-send timer, with random overhead* to avoid phase effects*/send_much(1, TCP_REASON_TIMEOUT, maxburst_);}}void RtxTimer::expire(Event *e) {a_->timeout(TCP_TIMER_RTX);}The various TCP agents contain additional examples of timers.114
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18 Radio Propagation Models 17718.1
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30 Multicast Routing 25130.1 Multic
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38.2.5 An example . . . . . . . . .
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X Other 40347 Educational use of NS
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# so, we lied. now, we define the t
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Chapter 2Undocumented FacilitiesNs
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Part IInterface to the Interpreter1
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• if you can do what you want by
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• tcl.result(const char* s)Pass t
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By convention in ns, the class Agen
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$object set bwvar 1500kb$object set
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For a C++ variable to be traceable,
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3.5 Class TclClassThis compiled cla
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class Packet {......static int hdrl
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The actual arguments passed by the
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class TclClass (Section 3.5) define
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Chapter 4The Class SimulatorThe ove
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4.2.2 the heap schedulerThe heap sc
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4.4 Commands at a glanceSynopsis:ns
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$ns_ dumpqCommand for dumping event
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NODEPortClassifierAgentAgentAddrCla
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The Node instance variable, entry_,
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The default values for all the abov
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The classify() method is pure virtu
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};The class imposes no direct seman
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flow-specific queuing disciplines a
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5.5 Routing Module and Classifier O
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Module NameRtModule/BaseRtModule/Mc
Page 63 and 64: $node neighborsThis returns the lis
Page 65 and 66: Linkhead_enqT_queue_ deqT_ link_ tt
Page 67 and 68: 6.2 ConnectorsConnectors, unlink cl
Page 69 and 70: $ns_ link-lossmodel This function
Page 71 and 72: Chapter 7Queue Management and Packe
Page 73 and 74: }}}void Queue::resume(){Packet* p =
Page 75 and 76: 7.3 Different types of Queue object
Page 77 and 78: maxidle_ is the maximum amount of t
Page 79 and 80: dst_ The destination address of pac
Page 81 and 82: 7.5.2 ConfigurationRunning a JoBS s
Page 83 and 84: mean_pkt_size_ Used to set the expe
Page 85 and 86: Demarker objects$q trace-file This
Page 87 and 88: The recv() method overrides the bas
Page 89 and 90: 9.2 ImplementationThe procedures an
Page 91 and 92: Average sending rateTSW window leng
Page 93 and 94: The following command adds an entry
Page 95 and 96: $qCE configQ 0 1 10 20 0.10Note tha
Page 97 and 98: Chapter 10AgentsAgents represent en
Page 99 and 100: CtrMcast/EncapCtrMcast/DecapMessage
Page 101 and 102: }bind("windowOption_", &wnd_option_
Page 103 and 104: hdr_flags* nf = (hdr_flags*)npkt->a
Page 105 and 106: public:ECHO_Timer(ECHO_Agent *a) :
Page 107 and 108: 10.6.4 Using the agent through OTcl
Page 109 and 110: State Variables are:dupacks_ Number
Page 111 and 112: $agent attach-tbf Attaches a token
Page 113: (void)Scheduler::instance().schedul
Page 117 and 118: Chapter 12Packet Headers and Format
Page 119 and 120: method is now obsolete; its usage i
Page 121 and 122: Packethdrsize_next_bits()points to
Page 123 and 124: the system’s memory allocator. In
Page 125 and 126: }incr hdrlen_ $incrreturn $baseFrom
Page 127 and 128: Chapter 13Error ModelThis chapter d
Page 129 and 130: SimpleLink::errormodule argsSimulat
Page 131 and 132: This is a simple example of how to
Page 133 and 134: Higher LayersNode 1Node 2. . .Node
Page 135 and 136: };void recv(Packet* p, Handler*);vi
Page 137 and 138: and the frame type. It then passes
Page 139 and 140: $ll_ set delay_ $delay$ll_ set band
Page 141 and 142: 14.10 Commands at a glanceThe follo
Page 143 and 144: 15.2.1 Default Hierarchical Setting
Page 145 and 146: Chapter 16Mobile Networking in nsTh
Page 147 and 148: entry_addrdemuxIP addressdefaulttar
Page 149 and 150: 16.1.2 Creating Node movementsThe m
Page 151 and 152: set netif $netif_($t)set mac $mac_(
Page 153 and 154: the hardware address of a packet’
Page 155 and 156: destined to itself to the port dmux
Page 157 and 158: switch(ch->ptype()) {case PT_MAC:br
Page 159 and 160: 16.1.7 Revised format for wireless
Page 161 and 162: Packet info at "Application level"
Page 163 and 164: The main problem facing the wired-c
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target_target_encapsulatorreg_agent
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why: This avoids header clashes bet
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This command is used to create a Go
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Chapter 17Satellite Networking in n
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in counter-rotating planes (where t
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• Position/Sat/Geo A geostationar
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$ns add-isl $ltype $node1 $node2 $b
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$satrouteobject_ compute_routeswher
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This will add an error model to the
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lh_firstnameobj‘‘name’’ is
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from routing agentto Node->entrySat
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$satnode add-isl This method c
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set prop [new Propagation/FreeSpace
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18.3.2 Using shadowing modelBefore
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Chapter 19Energy Model in nsEnergy
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Chapter 20Directed DiffusionThe dir
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However if we have a large and dens
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yr application in the ns context. T
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value of opt(pre-stop) is usually t
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21.2 Implementation of XCP in NSIn
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the persistent queue length in the
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Thruput2 0.054024 60000residue_pos_
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Chapter 22DelayBox: Per-Flow Delay
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$ns attach-agent $n_sink $sink# mak
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Chapter 23Changes made to the IEEE
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Part IIISupport214
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endenddocument pargvcPrint out argc
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24.4.2 Memory Conservation TipsSome
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Chapter 25Mathematical SupportThe s
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set run [lindex $argv 0]}if {$run <
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}$sizeRNG next-substream# print the
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protected:RNG* rng_;};Classes deriv
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ns-random is implemented in ~ns/mis
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Chapter 26Trace and Monitoring Supp
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The monitor-queue function is const
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also used to accumulate packet drop
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}name,th->size(),flags,iph->flowid(
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PT_TORA,PT_DSR,PT_AODV,// insert ne
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The QueueMonitor class is not deriv
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$ns_ trace-all This is the command
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Chapter 27Test Suite SupportThe ns
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... ...}$ns_ at $opt(stop).1 "$self
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Example: To enable debugging in Que
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Chapter 29Unicast RoutingThis secti
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Asymmetric Routing Asymmetric routi
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class RouteLogic This class defines
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— The procedure init-all{} is a g
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Global Actions Once the detailed ac
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This dumps next hop information in
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$ns mrtproto ST;# specify shared tr
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Dense Mode The Dense Mode protocol
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and unique label (id). Thus, “inc
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add-iif{ifid link},add-oif{link if}
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CtrMcastComp is the centralised mul
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$ns_ mrtproto This command specifi
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Chapter 31Network DynamicsThis chap
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v 0.8123 link-up 3 5v 0.8123 link-u
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The first argument is the time at w
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$ns_ rtmodel This command defines
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$ns set-address-format hierarchical
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32.4 Hierarchical Routing with Sess
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Chapter 33UDP Agents33.1 UDP Agents
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Chapter 34TCP AgentsThis section de
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set ns [new Simulator]set node1 [$n
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34.2.1 The Base TCP SinkThe base TC
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Agent/TCP/FullTcp set dupseg_fix_ t
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34.5 Tracing TCP DynamicsThe behavi
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Chapter 35SCTP AgentsThis chapter d
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Figure 35.1: Example of a Multihome
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Note: the actual value of these tra
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1.526624 1 4 sctp 1500 -------D 0 1
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$ns at 5.0 "finish"$ns run35.5.2 Mu
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Chapter 36Agent/SRMThis chapter des
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36.1.2 Other Configuration Paramete
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3.6274 n 0 m r 1 type repair servi
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3.6029 n 3 m r 2 Q NTIMER at 3.730
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36.4 Loss Detection—The Class SRM
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same packet. The repair objet does
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}hdr_asrm* seh = (hdr_asrm*) p->acc
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set grp [Node allocaddr]$srm set ds
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#set up the multicast routingDM set
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37.3 Architecture of the PLM Protoc
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We add in void PLMLossMonitor::recv
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Part VIApplication330
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Traffic generatorsApplication/Traff
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• recv(int nbytes)—Announces th
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1. EXPOO_Traffic—generates traffi
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set src [new Agent/UDP]set sink [ne
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Application FTP FTP objects produce
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send_data(ADU)Application(HttpApp,
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39.1.4 Transmitting user data over
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and teardown of connections. Only O
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TclObjectPagePoolPagePool/CompMathP
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PagePool/ProxyTrace takes these two
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}int id_; // object IDWebTrafSessio
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An Http/Server object waits for inc
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set tmp [new RandomVariable/Exponen
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Object Type Event Type Explaination
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Chapter 40Worm ModelIn this chapter
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$w local-p 0.5Following are some co
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(nsnode) clientcloudPackM ime(nsnod
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HTTP responsesclients servers Delay
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41.5 Commands at a GlanceThe follow
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• HTTP response size (bytes)• s
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Chapter 42Session-level Packet Dist
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42.1.2 Inserting a Loss ModuleWhen
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Delay and Loss Modules Each receive
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Chapter 43Asim: approximate analyti
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set n(1) [$ns node]set link(0:1) [$
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Part VIIIEmulation382
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When using the emulation mode, a sp
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set intf [$pf1 open readonly]puts "
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puts "install nets into taps..."$a0
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Chapter 45Nam45.1 IntroductionNam i
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• Button 6 (Chevron logo) - Close
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Second, when dealing with randomly
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dst_portaddr,seqno,flags,sname);A n
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• up• down• right• left•
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46.1.7 Agent TracingAgent trace eve
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v -t 1.0 -e node_tclscript 2 "Echo
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If nam ever gets to the end of an e
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l :link-t time-s source id-d des
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E :D :P :a :session enqueue-t time
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v :V :N :W :g :A :c :q :execute tcl
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$ns duplex-link-op orient right$ns
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Chapter 47Educational use of NS and
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Bibliography[1] C. Alaettinoğlu, A
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