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24.5.1 OTclOTcl, especially TclCL, provides a way to allocate new objects. However, it does not accordingly provide a garbage collectionmechanism for these allocated objects. This can easily lead to unintentional memory leaks. Important: tools such as dmallocand purify are unable to detect this kind of memory leaks. For example, consider this simple piece of OTcl script:set ns [new Simulator]for set i 0 $i < 500 incr iset a [new RandomVariable/Constant]One would expect that the memory usage should stay the same after the first RandomVariable is allocated. However, becauseOTcl does not have garbage collection, when the second RandomVariable is allocated, the previous one is not freed andhence results in memory leak. Unfortunately, there is no easy fix for this, because garbage collection of allocated objects isessentially incompatible with the spirit of Tcl. The only way to fix this now is to always explicitly free every allocated OTclobject in your script, in the same way that you take care of malloc-ed object in C/C++.24.5.2 C/C++Another source of memory leak is in C/C++. This is much easier to track given tools that are specifically designed for thistask, e.g., dmalloc and purify. nshas a special target ns-pure to build purified ns executable. First make sure that the macroPURIFY in the ns Makefile contains the right -collector for your linker (check purify man page if you don’t know what thisis). Then simply type make ns-pure. See earlier sections in this chapter on how to use ns with libdmalloc.219
Chapter 25Mathematical SupportThe simulator includes a small collection of mathematical functions used to implement random variate generation and integration.This area of the simulator is currently undergoing some changes.The procedures and functions described in this chapter can be found in ~ns/tools/rng.{cc, h}, ~ns/tools/random.{cc, h},~ns/tools/ranvar.{cc, h}, ~ns/tools/pareto.{cc, h}, ~ns/tools/expoo.{cc, h}, ~ns/tools/integrator.{cc, h}, and ~ns/tcl/lib/nsrandom.tcl.25.1 Random Number GenerationThe RNG class contains an implementation of the combined multiple recursive generator MRG32k3a proposed by L’Ecuyer[16]. The C++ code was adapted from [18]. This replaces the previous implementation of RNG, which used the minimalstandard multiplicative linear congruential generator of Park and Miller [27]. The newer (MRG32k3a) RNG is used in nsversions 2.1b9 and later.The MRG32k3a generator provides 1.8x10 19 independent streams of random numbers, each of which consists of 2.3x10 15substreams. Each substream has a period (i.e., the number of random numbers before overlap) of 7.6x10 22 . The period of theentire generator is 3.1x10 57 . Figure 25.1 provides a graphical idea of how the streams and substreams fit together.A default RNG (defaultRNG), created at simulator initialization time, is provided. If multiple random variables are used ina simulation, each random variable should use a separate RNG object. When a new RNG object is created, it is automaticallyseeded to the beginning of the next independent stream of random numbers. Used in this manner, the implementation allowsfor a maximum of 1.8x10 19 random variables.Often, multiple independent replications of a simulation are needed (i.e., to perform statistical analysis given multiple runswith fixed parameters). For each replication, a different substream should be used to ensure that the random number streamsare independent. (This process is given as an OTcl example later.) This implementation allows for a maximum of 2.3x10 15independent replications. Each random variable in a single replication can produce up to 7.6x10 22 random numbers beforeoverlapping.Note: Only the most common functions are described here. For more information, see [18] and the source code found intools/rng.h and tools/rng.cc. For a comparison of this RNG to the more common LCG16807 RNG (and whyLCG16807 is not a good RNG), see [17].220
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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
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$node neighborsThis returns the lis
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Linkhead_enqT_queue_ deqT_ link_ tt
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6.2 ConnectorsConnectors, unlink cl
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$ns_ link-lossmodel This function
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Chapter 7Queue Management and Packe
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}}}void Queue::resume(){Packet* p =
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7.3 Different types of Queue object
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maxidle_ is the maximum amount of t
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dst_ The destination address of pac
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7.5.2 ConfigurationRunning a JoBS s
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mean_pkt_size_ Used to set the expe
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Demarker objects$q trace-file This
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The recv() method overrides the bas
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9.2 ImplementationThe procedures an
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Average sending rateTSW window leng
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The following command adds an entry
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$qCE configQ 0 1 10 20 0.10Note tha
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Chapter 10AgentsAgents represent en
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CtrMcast/EncapCtrMcast/DecapMessage
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}bind("windowOption_", &wnd_option_
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hdr_flags* nf = (hdr_flags*)npkt->a
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public:ECHO_Timer(ECHO_Agent *a) :
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10.6.4 Using the agent through OTcl
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State Variables are:dupacks_ Number
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$agent attach-tbf Attaches a token
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(void)Scheduler::instance().schedul
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* outstanding, cancel it.*/void Tcp
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Chapter 12Packet Headers and Format
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method is now obsolete; its usage i
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Packethdrsize_next_bits()points to
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the system’s memory allocator. In
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}incr hdrlen_ $incrreturn $baseFrom
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Chapter 13Error ModelThis chapter d
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SimpleLink::errormodule argsSimulat
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This is a simple example of how to
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Higher LayersNode 1Node 2. . .Node
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};void recv(Packet* p, Handler*);vi
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and the frame type. It then passes
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$ll_ set delay_ $delay$ll_ set band
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14.10 Commands at a glanceThe follo
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15.2.1 Default Hierarchical Setting
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Chapter 16Mobile Networking in nsTh
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entry_addrdemuxIP addressdefaulttar
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16.1.2 Creating Node movementsThe m
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set netif $netif_($t)set mac $mac_(
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the hardware address of a packet’
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destined to itself to the port dmux
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switch(ch->ptype()) {case PT_MAC:br
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16.1.7 Revised format for wireless
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Packet info at "Application level"
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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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Page 171 and 172: Chapter 17Satellite Networking in n
Page 173 and 174: in counter-rotating planes (where t
Page 175 and 176: • Position/Sat/Geo A geostationar
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Page 179 and 180: $satrouteobject_ compute_routeswher
Page 181 and 182: This will add an error model to the
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Page 187 and 188: $satnode add-isl This method c
Page 189 and 190: set prop [new Propagation/FreeSpace
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Page 193 and 194: Chapter 19Energy Model in nsEnergy
Page 195 and 196: Chapter 20Directed DiffusionThe dir
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Page 203 and 204: 21.2 Implementation of XCP in NSIn
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Page 209 and 210: Chapter 22DelayBox: Per-Flow Delay
Page 211 and 212: $ns attach-agent $n_sink $sink# mak
Page 213 and 214: Chapter 23Changes made to the IEEE
Page 215 and 216: Part IIISupport214
Page 217 and 218: endenddocument pargvcPrint out argc
Page 219: 24.4.2 Memory Conservation TipsSome
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Page 225 and 226: }$sizeRNG next-substream# print the
Page 227 and 228: protected:RNG* rng_;};Classes deriv
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Page 231 and 232: Chapter 26Trace and Monitoring Supp
Page 233 and 234: The monitor-queue function is const
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Page 239 and 240: PT_TORA,PT_DSR,PT_AODV,// insert ne
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Page 245 and 246: Chapter 27Test Suite SupportThe ns
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Page 249 and 250: Example: To enable debugging in Que
Page 251 and 252: Chapter 29Unicast RoutingThis secti
Page 253 and 254: Asymmetric Routing Asymmetric routi
Page 255 and 256: class RouteLogic This class defines
Page 257 and 258: — The procedure init-all{} is a g
Page 259 and 260: Global Actions Once the detailed ac
Page 261 and 262: This dumps next hop information in
Page 263 and 264: $ns mrtproto ST;# specify shared tr
Page 265 and 266: Dense Mode The Dense Mode protocol
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CtrMcastComp is the centralised mul
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$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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