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class Link This class supports the primitives: up and down, and up? to set and query status_. These primitives areinstance procedures of the class.The instance procedures up{} and down{} set status_ to 1 and 0 respectively.In addition, when the link fails, down{} will reset all connectors that make up the link. Each connector, including allqueues and the delay object will flush and drop any packets that it currently stores. This emulates the packet drop dueto link failure.Both procedures then write trace entries to each file handle in the list, dynT_.The instance procedure up?{} returns the current value of status_.In addition, the class contains the instance procedure all-connectors{}. This procedure takes an operation as argument,and applies the operation uniformly to all of the class instance variables that are handles for TclObjects.class SimpleLink The class supports two instance procedures dynamic{} and trace-dynamics{}. We havealready described the latter procedure when describing the trace{} procedure in the class rtModel.The instance procedure dynamic{} inserts a DynamicLink object (Section 6.2) at the head of the queue. It points the downtargetof the object to the drop target of the link, drpT_, if the object is defined, or to the nullAgent_ in the simulator. Italso signals each connector in the link that the link is now dynamic.Most connectors ignore this signal to be become dynamic; the exception is DelayLink object. This object will normallyschedule each packet it receives for reception by the destination node at the appropriate time. When the link is dynamic,the object will queue each packet internally; it schedules only one event for the next packet that will be delivered, instead ofone event per packet normally. If the link fails, the route model will signal a reset, at which point, the shadow object willexecute its reset instproc-like, and flush all packets in its internal queue. Additional details about the DelayLink can be foundin another chapter (Chapter 8).31.4 Deficencies in the Current Network Dynamics APIThere are a number of deficencies in the current API that should be changed in the next iteration:1. There is no way to specify a cluster of nodes or links that behave in lock-step dynamic synchrony.2. Node failure should be dealt with as its own mechanism, rather than a second grade citizen of link failure. This showsup in a number of situations, such as:(a) The method of emulating node failure as the failure of the incident links is broken. Ideally, node failure shouldcause all agents incident on the node to be reset.(b) There is no tracing associated with node failure.3. If two distinct route models are applied to two separate links incident on a common node, and the two links experiencea topology change at the same instant, then the node will be notified more than once.31.5 Commands at a glanceFollowing is a list of commands used to simulate dynamic scenarios in ns:279
$ns_ rtmodel This command defines the dynamic model (currently implemented models are: Deterministic, Exponential, Manual orTrace) to be applied to nodes and links in the topology. The first two arguments consists of the rtmodel and the parameter toconfigure the model. stands for different type of arguments expected with different dynamic model types. Thisreturns a handle to a model object corresponding to the specified model.• In the Deterministic model is , , , . Startingfrom start-time the link is made up for up-interval and down for down-interval till finish-time is reached. The defaultvalues for start-time, up-interval, downinterval are 0.5s, 2.0s, 1.0s respectively. finishtime defaults to the end of thesimulation. The start-time defaults to 0.5s in order to let the routing protocol computation quiesce.• If the Exponential model is used model-params is of the form , where the link up-timeis an exponential distribution around the mean upinterval and the link down-time is an exponential distribution aroundthe mean down-interval. Default values for up-interval and down-interval are 10s and 1s respectively.• If the Manual distribution is used model-params is where at specifies the time at which the operation opshould occur. op is one of up, down. The Manual distribution could be specified alternately using the rtmodel-atmethod described later in the section.• If Trace is specified as the model the link/node dynamics is read from a Tracefile. The model-params argument wouldin this case be the file-handle of the Tracefile that has the dynamics information. The tracefile format is identical to thetrace output generated by the trace-dynamics link method (see TRACE AND MONITORING METHODS SECTION).$ns_ rtmodel-delete This command takes the handle of the routemodel as an argument, removes it from the list of rtmodels maintainedby simulator and deletes the model.$ns_ rtmodel-at This command is a special interface to the Manual model of network dynamics. It takes the time , type of operation and node or link on which to apply the operation as the arguments. At time , the operation whichmaybe up or down is applied to a node or link.$rtmodel trace This enables tracing of dynamics effected by this model in the links. is an instance of the simulator, the output fileto write the traces to and is an optional argument that may be used to define a type of operation (like nam). This is awrapper for the class Link procedure trace-dynamics.$link trace-dynamics This is a class link instance procedure that is used to setup tracing of dynamics in that particular link. The arguments aresame as that of class rtModel’s procedure trace described above.$link dynamicThis command inserts a DynamicLink object at the head of the queue and signals to all connectors in the link that the link isnow dynamic.Internal procedures:$ns_ rtmodel-configureThis is an internal procedure that configures all dynamic models that are present in the list of models maintained by thesimulator.280
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18 Radio Propagation Models 17718.1
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30 Multicast Routing 25130.1 Multic
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38.2.5 An example . . . . . . . . .
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X Other 40347 Educational use of NS
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# so, we lied. now, we define the t
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Chapter 2Undocumented FacilitiesNs
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Part IInterface to the Interpreter1
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• if you can do what you want by
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• tcl.result(const char* s)Pass t
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By convention in ns, the class Agen
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$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 $mac_(
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the hardware address of a packet’
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destined to itself to the port dmux
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switch(ch->ptype()) {case PT_MAC:br
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16.1.7 Revised format for wireless
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Packet info at "Application level"
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The main problem facing the wired-c
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target_target_encapsulatorreg_agent
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why: This avoids header clashes bet
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This command is used to create a Go
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Chapter 17Satellite Networking in n
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in counter-rotating planes (where t
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• Position/Sat/Geo A geostationar
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$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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Page 231 and 232: Chapter 26Trace and Monitoring Supp
Page 233 and 234: The monitor-queue function is const
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Page 237 and 238: }name,th->size(),flags,iph->flowid(
Page 239 and 240: PT_TORA,PT_DSR,PT_AODV,// insert ne
Page 241 and 242: The QueueMonitor class is not deriv
Page 243 and 244: $ns_ trace-all This is the command
Page 245 and 246: Chapter 27Test Suite SupportThe ns
Page 247 and 248: ... ...}$ns_ at $opt(stop).1 "$self
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
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Page 263 and 264: $ns mrtproto ST;# specify shared tr
Page 265 and 266: Dense Mode The Dense Mode protocol
Page 267 and 268: and unique label (id). Thus, “inc
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Page 271 and 272: CtrMcastComp is the centralised mul
Page 273 and 274: $ns_ mrtproto This command specifi
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Page 277 and 278: v 0.8123 link-up 3 5v 0.8123 link-u
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Page 283 and 284: $ns set-address-format hierarchical
Page 285 and 286: 32.4 Hierarchical Routing with Sess
Page 287 and 288: Chapter 33UDP Agents33.1 UDP Agents
Page 289 and 290: Chapter 34TCP AgentsThis section de
Page 291 and 292: set ns [new Simulator]set node1 [$n
Page 293 and 294: 34.2.1 The Base TCP SinkThe base TC
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Page 297 and 298: 34.5 Tracing TCP DynamicsThe behavi
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Page 301 and 302: Figure 35.1: Example of a Multihome
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Page 307 and 308: $ns at 5.0 "finish"$ns run35.5.2 Mu
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Page 311 and 312: 36.1.2 Other Configuration Paramete
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Page 317 and 318: 36.4 Loss Detection—The Class SRM
Page 319 and 320: same packet. The repair objet does
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Page 323 and 324: set grp [Node allocaddr]$srm set ds
Page 325 and 326: #set up the multicast routingDM set
Page 327 and 328: 37.3 Architecture of the PLM Protoc
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Part VIApplication330
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Traffic generatorsApplication/Traff
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• recv(int nbytes)—Announces th
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1. EXPOO_Traffic—generates traffi
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set src [new Agent/UDP]set sink [ne
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Application FTP FTP objects produce
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send_data(ADU)Application(HttpApp,
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39.1.4 Transmitting user data over
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and teardown of connections. Only O
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TclObjectPagePoolPagePool/CompMathP
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PagePool/ProxyTrace takes these two
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}int id_; // object IDWebTrafSessio
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An Http/Server object waits for inc
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set tmp [new RandomVariable/Exponen
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Object Type Event Type Explaination
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Chapter 40Worm ModelIn this chapter
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$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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