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Agent/TCP set cwnd_ 0Agent/TCP set awnd_ 0Agent/TCP set ssthresh_ 0Agent/TCP set rtt_ 0Agent/TCP set srtt_ 0Agent/TCP set rttvar_ 0Agent/TCP set backoff_ 0Agent/TCP set maxseq_ 0;# congestion window (packets);# averaged cwnd (experimental);# slow-stat threshold (packets);# rtt sample;# smoothed (averaged) rtt;# mean deviation of rtt samples;# current RTO backoff factor;# max (packet) seq number sentFor many simulations, few of the configuration parameters are likely to require modification. The more commonly modifiedparameters include: window_ and packetSize_. The first of these bounds the window TCP uses, and is considered toplay the role of the receiver’s advertised window in real-world TCP (although it remains constant). The packet size essentiallyfunctions like the MSS size in real-world TCP. Changes to these parameters can have a profound effect on the behavior ofTCP. Generally, those TCPs with larger packet sizes, bigger windows, and smaller round trip times (a result of the topologyand congestion) are more agressive in acquiring network bandwidth.34.1.5 Other One-Way TCP SendersReno TCP The Reno TCP agent is very similar to the Tahoe TCP agent, except it also includes fast recovery, where thecurrent congestion window is “inflated” by the number of duplicate ACKs the TCP sender has received before receiving anew ACK. A “new ACK” refers to any ACK with a value higher than the higest seen so far. In addition, the Reno TCP agentdoes not return to slow-start during a fast retransmit. Rather, it reduces sets the congestion window to half the current windowand resets ssthresh_ to match this value.Newreno TCP This agent is based on the Reno TCP agent, but which modifies the action taken when receiving new ACKS.In order to exit fast recovery, the sender must receive an ACK for the highest sequence number sent. Thus, new “partialACKs” (those which represent new ACKs but do not represent an ACK for all outstanding data) do not deflate the window(and possibly lead to a stall, characteristic of Reno).Vegas TCPThis agent implements “Vegas” TCP ([4, 5]). It was contributed by Ted Kuo.Sack TCP This agent implements selective repeat, based on selective ACKs provided by the receiver. It follows the ACKscheme described in [23], and was developed with Matt Mathis and Jamshid Mahdavi.Fack TCP This agent implements “forward ACK” TCP, a modification of Sack TCP described in [22].34.2 TCP Receivers (sinks)The TCP senders described above represent one-way data senders. They must peer with a “TCP sink” object.291
34.2.1 The Base TCP SinkThe base TCP sink object (Agent/TCPSink) is responsible for returning ACKs to a peer TCP source object. It generatesone ACK per packet received. The size of the ACKs may be configured. The creation and configuration of the TCP sinkobject is generally performed automatically by a library call (see create-connection above).configuration parametersAgent/TCPSink set packetSize_ 4034.2.2 Delayed-ACK TCP SinkA delayed-ACK sink object (Agent/Agent/TCPSink/DelAck) is available for simulating a TCP receiver that ACKsless than once per packet received. This object contains a bound variable interval_ which gives the number of seconds towait between ACKs. The delayed ACK sink implements an agressive ACK policy whereby only ACKs for in-order packetsare delayed. Out-of-order packets cause immediate ACK generation.configuration parametersAgent/TCPSink/DelAck set interval_ 100ms34.2.3 Sack TCP SinkThe selective-acknowledgment TCP sink (Agent/TCPSink/Sack1) implements SACK generation modeled after the descriptionof SACK in RFC 2018. This object includes a bound variable maxSackBlocks_ which gives the maximumnumber of blocks of information in an ACK available for holding SACK information. The default value for this variable is 3,in accordance with the expected use of SACK with RTTM (see RFC 2018, section 3). Delayed and selective ACKs togetherare implemented by an object of type Agent/TCPSink/Sack1/DelAck.configuration parametersAgent/TCPSink set maxSackBlocks_ 334.3 Two-Way TCP Agents (FullTcp)The Agent/TCP/FullTcp object is a new addition to the suite of TCP agents supported in the simulator and is still underdevelopment. It is different from (and incompatible with) the other agents, but does use some of the same architecture. Itdiffers from these agents in the following ways: following ways:• connections may be establised and town down (SYN/FIN packets are exchanged)• bidirectional data transfer is supported292
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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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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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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
Page 267 and 268: and unique label (id). Thus, “inc
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Page 271 and 272: CtrMcastComp is the centralised mul
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Page 275 and 276: Chapter 31Network DynamicsThis chap
Page 277 and 278: v 0.8123 link-up 3 5v 0.8123 link-u
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Page 281 and 282: $ns_ rtmodel This command defines
Page 283 and 284: $ns set-address-format hierarchical
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Page 287 and 288: Chapter 33UDP Agents33.1 UDP Agents
Page 289 and 290: Chapter 34TCP AgentsThis section de
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Page 295 and 296: Agent/TCP/FullTcp set dupseg_fix_ t
Page 297 and 298: 34.5 Tracing TCP DynamicsThe behavi
Page 299 and 300: Chapter 35SCTP AgentsThis chapter d
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 331 and 332: Part VIApplication330
Page 333 and 334: Traffic generatorsApplication/Traff
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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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