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implemented in a single Mac object. For sending, the Mac object must follow a certain medium access protocol beforetransmitting the packet on the channel. For receiving, the MAC layer is responsible for delivering the packet to the link layer.Above the MAC layer, the link layer can potentially have many functionalities such as queuing and link-level retransmission.The need of having a wide variety of link-level schemes leads to the division of functionality into two components: Queueand LL (link-layer). The Queue object, simulating the interface queue, belongs to the same Queue class that is describedin Chapter 7. The LL object implements a particular data link protocol, such as ARQ. By combining both the sending andreceiving functionalities into one module, the LL object can also support other mechanisms such as piggybacking.14.3 Channel ClassThe Channel class simulates the actual transmission of the packet at the physical layer. The basic Channel implementsa shared medium with support for contention mechanisms. It allows the MAC to carry out carrier sense, contention, andcollision detection. If more than one transmissions overlaps in time, a channel raises the collision flag. By checking this flag,the MAC object can implement collision detection and handling.Since the transmission time is a function of the number of bits in the packet and the modulation speed of each individualinterface (MAC), the Channel object only sets its busy signal for the duration requested by the MAC object. It alsoschedules the packets to be delivered to the destination MAC objects after the transmission time plus the propagation delay.14.3.1 Channel StateThe C++ class Channel includes enough internal state to schedule packet delivery and detect collisions. It exports thefollowing OTcl configuration parameter:delay_propagation delay on the channel14.3.2 Example: Channel and classifier of the physical layerset channel_ [new Channel]$channel_ set delay_ 4us# propagation delayset mcl_ [new Classifier/Mac]$channel_ target $mcl_$mcl_ install $mac_DA $recv_iface. . .14.3.3 Channel Class in C++In C++, the class Channel extends the Connector object with several new methods to support a variety of MAC protocols.The class is defined as follow in ~ns/channel.h:class Channel : public Connector {public:Channel();133
};void recv(Packet* p, Handler*);virtual int send(Packet* p, double txtime);virtual void contention(Packet*, Handler*);int hold(double txtime);virtual int collision() { return numtx_ > 1; }virtual double txstop() { return txstop_; }. . .The important methods of the class Channel are:• txstop() method returns the time when the channel will become idle, which can be used by the MAC to implementcarrier sense.• contention() method allows the MAC to contend for the channel before sending a packet. The channel then usethis packet to signal the corresponding Mac object at the end of each contention period.• collision() method indicates whether a collision occurs during the contention period. When the Channel signalthe end of the contention period, the MAC can use the collision() method to detect collision.• send() method allows the MAC object to transmit a packet on the channel for a specified duration of time.• hold() method allows the MAC object to hold the channel for a specified duration of time without actually transmittingany packets. This is useful in simulating the jamming mechanism of some MAC protocols.14.4 MacClassifier ClassThe MacClassifier class extends the Classifier class to implement a simple broadcasting mechanism. It modifiesthe recv() method in the following way: since the replication of a packet is expensive, normally a unicast packet willbe classified by the MAC destination address macDA_ and delivered directly to the MAC object with such an address.However, if the destination object cannot be found or if the MAC destination address is explicitly set to the broadcast addressBCAST_ADDR, the packet will be replicated and sent to all MACs on the lan excluding the one that is the source of the packet.Finally, by setting the bound variable MacClassifier::bcast_ to a non–zero value, will cause MacClassifieralways to replicate packets.class MacClassifier : public Classifier {public:void recv(Packet*, Handler*);};void MacClassifier::recv(Packet* p, Handler*){Mac* mac;hdr_mac* mh = hdr_mac::access(p);}if (bcast_ || mh->macDA() == BCAST_ADDR || (mac = (Mac *)find(p)) == 0) {// Replicate packets to all slots (broadcast). . .return;}mac->recv(p);134
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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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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
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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 and 114: (void)Scheduler::instance().schedul
Page 115 and 116: * outstanding, cancel it.*/void Tcp
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: Higher LayersNode 1Node 2. . .Node
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 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
Page 165 and 166: target_target_encapsulatorreg_agent
Page 167 and 168: why: This avoids header clashes bet
Page 169 and 170: This command is used to create a Go
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
Page 177 and 178: $ns add-isl $ltype $node1 $node2 $b
Page 179 and 180: $satrouteobject_ compute_routeswher
Page 181 and 182: This will add an error model to the
Page 183 and 184: lh_firstnameobj‘‘name’’ is
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from routing agentto Node->entrySat
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$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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