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Counter-rotating planescause rapid ‘‘crossseam’’ISL handoffsOverlap of coverage at the polesInterplane intersatellitelinks (ISLs) are turned offAn ‘‘intraplane’’ ISLAn ‘‘interplane’’ ISLFigure 17.1: Example of a polar-orbiting LEO constellation. This figure was generated using the SaVi software package fromthe geometry center at the University of Minnesota.simulate MAC protocols. Users can now define many terminals at different locations on the Earth’s surface and connect themto the same satellite uplink and downlink channels, and the propagation delays in the system (which are slightly different foreach user) are accurately modelled. In addition, the uplink and downlink channels can be defined differently (perhaps withdifferent bandwidths or error models).17.1.2 Low-earth-orbiting satellitesPolar orbiting satellite systems, such as Iridium and the proposed Teledesic system, can be modelled in ns. In particular, thesimulator supports the specification of satellites that orbit in purely circular planes, for which the neighboring planes are corotating.There are other non-geostationary constellation configurations possible (e.g., Walker constellations)– the interesteduser may develop new constellation classes to simulate these other constellation types. In particular, this would mainly requiredefining new intersatellite link handoff procedures.The following are the parameters of satellite constellations that can currently be simulated:• Basic constellation definition Includes satellite altitude, number of satellites, number of planes, number of satellitesper plane.• Orbits Orbit inclination can range continuously from 0 to 180 degrees (inclination greater than 90 degrees correspondsto retrograde orbits). Orbit eccentricity is not modeled. Nodal precession is not modeled. Intersatellite spacing within agiven plane is fixed. Relative phasing between planes is fixed (although some systems may not control phasing betweenplanes).• Intersatellite (ISL) links For polar orbiting constellations, intraplane, interplane, and crossseam ISLs can be defined.Intraplane ISLs exist between satellites in the same plane and are never deactivated or handed off. Interplane ISLs existbetween satellites of neighboring co-rotating planes. These links are deactivated near the poles (above the “ISL latitudethreshold” in the table) because the antenna pointing mechanism cannot track these links in the polar regions. Likeintraplane ISLs, interplane ISLs are never handed off. Crossseam ISLs may exist in a constellation between satellites171
in counter-rotating planes (where the planes form a so-called “seam” in the topology). GEO ISLs can also be definedfor constellations of geostationary satellites.• Ground to satellite (GSL) links Multiple terminals can be connected to a single GSL satellite channel. GSL links forGEO satellites are static, while GSL links for LEO channels are periodically handed off as described below.• Elevation mask The elevation angle above which a GSL link can be operational. Currently, if the (LEO) satelliteserving a terminal drops below the elevation mask, the terminal searches for a new satellite above the elevation mask.Satellite terminals check for handoff opportunities according to a timeout interval specified by the user. Each terminalinitiates handoffs asynchronously; it would be possible also to define a system in which each handoff occurssynchronously in the system.The following table lists parameters used for example simulation scripts of the Iridium 1 and Teledesic 2 systems.Iridium TeledesicAltitude 780 km 1375 kmPlanes 6 12Satellites per plane 11 24Inclination (deg) 86.4 84.7Interplane separation (deg) 31.6 15Seam separation (deg) 22 15Elevation mask (deg) 8.2 40Intraplane phasing yes yesInterplane phasing yes noISLs per satellite 4 8ISL bandwidth 25 Mb/s 155 Mb/sUp/downlink bandwidth 1.5 Mb/s 1.5 Mb/sCross-seam ISLs no yesISL latitude threshold (deg) 60 60Table 17.1: Simulation parameters used for modeling a broadband version of the Iridium system and the proposed 288-satelliteTeledesic system. Both systems are examples of polar orbiting constellations.1 Aside from the link bandwidths (Iridium is a narrowband system only), these parameters are very close to what a broadband version of the Iridiumsystem might look like.2 These Teledesic constellation parameters are subject to change; thanks to Marie-Jose Montpetit of Teledesic for providing tentative parameters as ofJanuary 1999. The link bandwidths are not necessarily accurate.172
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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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Page 127 and 128: Chapter 13Error ModelThis chapter d
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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_(
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Page 161 and 162: Packet info at "Application level"
Page 163 and 164: The main problem facing the wired-c
Page 165 and 166: target_target_encapsulatorreg_agent
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Page 171: Chapter 17Satellite Networking in n
Page 175 and 176: • Position/Sat/Geo A geostationar
Page 177 and 178: $ns add-isl $ltype $node1 $node2 $b
Page 179 and 180: $satrouteobject_ compute_routeswher
Page 181 and 182: This will add an error model to the
Page 183 and 184: lh_firstnameobj‘‘name’’ is
Page 185 and 186: from routing agentto Node->entrySat
Page 187 and 188: $satnode add-isl This method c
Page 189 and 190: set prop [new Propagation/FreeSpace
Page 191 and 192: 18.3.2 Using shadowing modelBefore
Page 193 and 194: Chapter 19Energy Model in nsEnergy
Page 195 and 196: Chapter 20Directed DiffusionThe dir
Page 197 and 198: However if we have a large and dens
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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
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Page 221 and 222: 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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