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• sequence numbers are in bytes rather than packetsThe generation of SYN packets (and their ACKs) can be of critical importance in trying to model real-world behavior whenusing many very short data transfers. This version of TCP currently defaults to sending data on the 3rd segment of an initial 3-way handshake, a behavior somewhat different than common real-world TCP implementations. A “typical” TCP connectionproceeds with an active opener sending a SYN, the passive opener responding with a SYN+ACK, the active opener respondingwith an ACK, and then some time later sending the first segment with data (corresponding to the first application write). Thus,this version of TCP sends data at a time somewhat earlier than typical implementations. This TCP can also be configured tosend data on the initial SYN segment. Future changes to FullTCP may include a modification to send the first data segmentlater, and possibly to implement T/TCP functionality.Currently FullTCP is only implemented with Reno congestion control, but ultimately it should be available with the full rangeof congestion control algorithms (e.g., Tahoe, SACK, Vegas, etc.).34.3.1 Simple ConfigurationRunning an Full TCP simulation requires creating and configuring the agent, attaching an application-level data source (atraffic generator), and starting the agent and the traffic generator.Creating the Agent# set up connection (do not use "create-connection" method because# we need a handle on the sink object)set src [new Agent/TCP/FullTcp]set sink [new Agent/TCP/FullTcp]$ns_ attach-agent $node_(s1) $src$ns_ attach-agent $node_(k1) $sink$src set fid_ 0$sink set fid_ 0$ns_ connect $src $sink# set up TCP-level connections$sink listen$src set window_ 100;;# create agent;# create agent;# bind src to node;# bind sink to node;# set flow ID field;# set flow ID field;# active connection src to sink;# will figure out who its peer isThe creation of the FullTcp agent is similar to the other agents, but the sink is placed in a listening state by the listenmethod. Because a handle to the receiving side is required in order to make this call, the create-connection call usedabove cannot be used.Configuration ParametersThe following configuration parameters are available through Tcl for the FullTcp agent:Agent/TCP/FullTcp set segsperack_ 1Agent/TCP/FullTcp set segsize_ 536Agent/TCP/FullTcp set tcprexmtthresh_ 3Agent/TCP/FullTcp set iss_ 0Agent/TCP/FullTcp set nodelay_ falseAgent/TCP/FullTcp set data_on_syn_ false;# segs received before generating ACK;# segment size (MSS size for bulk xfers);# dupACKs thresh to trigger fast rexmt;# initial send sequence number;# disable sender-side Nagle algorithm;# send data on initial SYN?293
Agent/TCP/FullTcp set dupseg_fix_ true;# avoid fast rxt due to dup segs+acksAgent/TCP/FullTcp set dupack_reset_ false ;# reset dupACK ctr on !0 len data segs containing dup ACKsAgent/TCP/FullTcp set interval_ 0.1;# as in TCP above, (100ms is non-std)34.3.2 BayFullTcpA different implementation of two-way TCP has been ported into ns from Kathy Nicholes/Van Jacobson’s group. It is calledBayFullTcp. The basic difference between BayFullTcp and FullTcp (the two-way tcp version already present in ns) are asfollows:• BayTcp supports a client-server application model while FullTcp makes no assumption about its application layer.• The tcp-application interface is different for both;• FullTcp supports partial ack (BayTcp doesn’t).• FullTcp supports different flavors of tcp (tahoe, reno etc) which is not the case for baytcp.• Both implementations have different set of API’s .There might be other finer differences between the two as well. One of our future plans is to redefine the APIs to allow fulltcpto use baytcp’s client-server model.34.4 Architecture and InternalsThe base TCP agent (class Agent/TCP) is constructed as a collection of routines for sending packets, processing ACKs,managing the send window, and handling timeouts. Generally, each of these routines may be over-ridden by a function withthe same name in a derived class (this is how many of the TCP sender variants are implemented).The TCP header The TCP header is defined by the hdr_tcp structure in the file ~ns/tcp.h. The base agent only makesuse of the following subset of the fields:ts_ /* current time packet was sent from source */ts_echo_ /* for ACKs: timestamp field from packet associated with this ACK */seqno_ /* sequence number for this data segment or ACK (Note: overloading!) */reason_ /* set by sender when (re)transmitting to trace reason for send */Functions for Sending DataNote that generally the sending TCP never actually sends data (it only sets the packet size).send_much(force, reason, maxburst) - this function attempts to send as many packets as the current sent window allows. Italso keeps track of how many packets it has sent, and limits to the total to maxburst.The function output(seqno, reason) sends one packet with the given sequence number and updates the maximumsent sequence number variable (maxseq_) to hold the given sequence number if it is the greatest sent so far. This functionalso assigns the various fields in the TCP header (sequence number, timestamp, reason for transmission). This function alsosets a retransmission timer if one is not already pending.294
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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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The QueueMonitor class is not deriv
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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 265 and 266: Dense Mode The Dense Mode protocol
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Page 271 and 272: CtrMcastComp is the centralised mul
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Page 281 and 282: $ns_ rtmodel This command defines
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Page 329 and 330: We add in void PLMLossMonitor::recv
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Page 333 and 334: Traffic generatorsApplication/Traff
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39.1.4 Transmitting user data over
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and teardown of connections. Only O
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TclObjectPagePoolPagePool/CompMathP
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PagePool/ProxyTrace takes these two
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}int id_; // object IDWebTrafSessio
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An Http/Server object waits for inc
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set tmp [new RandomVariable/Exponen
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Object Type Event Type Explaination
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Chapter 40Worm ModelIn this chapter
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$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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