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PacketQueue objects. The PacketQueue class maintains current counts of the number of packets held in the queuewhich is returned by the length() method. The enque function places the specified packet at the end of the queue andupdates the len_ member variable. The deque function returns the packet at the head of the queue and removes it fromthe queue (and updates the counters), or returns NULL if the queue is empty. The lookup function returns the nth packetfrom the head of the queue, or NULL otherwise. The remove function deletes the packet stored in the given address fromthe queue (and updates the counters). It causes an abnormal program termination if the packet does not exist.7.2 Example: Drop TailThe following example illustrates the implementation of the Queue/DropTail object, which implements FIFO schedulingand drop-on-overflow buffer management typical of most present-day Internet routers. The following definitions declare theclass and its OTcl linkage:/** A bounded, drop-tail queue*/class DropTail : public Queue {protected:void enque(Packet*);Packet* deque();PacketQueue q_;};The base class Queue, from which DropTail is derived, provides most of the needed functionality. The drop-tail queuemaintains exactly one FIFO queue, implemented by including an object of the PacketQueue class. Drop-tail implementsits own versions of enque and deque as follows:/** drop-tail*/void DropTail::enque(Packet* p){q_.enque(p);if (q_.length() >= qlim_) {q_.remove(p);drop(p);}}Packet* DropTail::deque(){return (q_.deque());}Here, the enque function first stores the packet in the internal packet queue (which has no size restrictions), and then checksthe size of the packet queue versus qlim_. Drop-on-overflow is implemented by dropping the packet most recently addedto the packet queue if the limit is reached or exceeded. Note: in the implementation of enque above, setting qlim_ to nactually means a queue size of n-1. Simple FIFO scheduling is implemented in the deque function by always returning thefirst packet in the packet queue.73
7.3 Different types of Queue objectsA queue object is a general class of object capable of holding and possibly marking or discarding packets as they travelthrough the simulated topology. Configuration Parameters used for queue objects are:limit_ The queue size in packets.blocked_ Set to false by default, this is true if the queue is blocked (unable to send a packet to its downstream neighbor).unblock_on_resume_ Set to true by default, indicates a queue should unblock itself at the time the last packet packet senthas been transmitted (but not necessarily received).Other queue objects derived from the base class Queue are drop-tail, FQ, SFQ, DRR, RED and CBQ queue objects. Each aredescribed as follows:• Drop-tail objects: Drop-tail objects are a subclass of Queue objects that implement simple FIFO queue. There are nomethods, configuration parameter, or state variables that are specific to drop-tail objects.• FQ objects: FQ objects are a subclass of Queue objects that implement Fair queuing. There are no methods that arespecific to FQ objects. Configuration Parameters are:secsPerByte_There are no state variables associated with this object.• SFQ objects: SFQ objects are a subclass of Queue objects that implement Stochastic Fair queuing. There are nomethods that are specific to SFQ objects. Configuration Parameters are:maxqueue_buckets_There are no state variables associated with this object.• DRR objects: DRR objects are a subclass of Queue objects that implement deficit round robin scheduling. Theseobjects implement deficit round robin scheduling amongst different flows ( A particular flow is one which has packetswith the same node and port id OR packets which have the same node id alone). Also unlike other multi-queue objects,this queue object implements a single shared buffer space for its different flows. Configuration Parameters are:buckets_ Indicates the total number of buckets to be used for hashing each of the flows.blimit_ Indicates the shared buffer size in bytes.quantum_ Indicates (in bytes) how much each flow can send during its turn.mask_ mask_, when set to 1, means that a particular flow consists of packets having the same node id (and possiblydifferent port ids), otherwise a flow consists of packets having the same node and port ids.• RED objects: RED objects are a subclass of Queue objects that implement random early-detection gateways. Theobject can be configured to either drop or “mark” packets. There are no methods that are specific to RED objects.Configuration Parameters are:bytes_ Set to "true" to enable “byte-mode” RED, where the size of arriving packets affect the likelihood of marking(dropping) packets.queue-in-bytes_ Set to "true" to measure the average queue size in bytes rather than packets. Enabling this option alsocauses thresh_ and maxthresh_ to be automatically scaled by mean_pktsize_ (see below).thresh_ The minimum threshold for the average queue size in packets.74
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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
Page 23 and 24: • tcl.result(const char* s)Pass t
Page 25 and 26: By convention in ns, the class Agen
Page 27 and 28: $object set bwvar 1500kb$object set
Page 29 and 30: For a C++ variable to be traceable,
Page 31 and 32: 3.5 Class TclClassThis compiled cla
Page 33 and 34: class Packet {......static int hdrl
Page 35 and 36: The actual arguments passed by the
Page 37 and 38: class TclClass (Section 3.5) define
Page 39 and 40: Chapter 4The Class SimulatorThe ove
Page 41 and 42: 4.2.2 the heap schedulerThe heap sc
Page 43 and 44: 4.4 Commands at a glanceSynopsis:ns
Page 45 and 46: $ns_ dumpqCommand for dumping event
Page 47 and 48: NODEPortClassifierAgentAgentAddrCla
Page 49 and 50: The Node instance variable, entry_,
Page 51 and 52: The default values for all the abov
Page 53 and 54: The classify() method is pure virtu
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Page 57 and 58: flow-specific queuing disciplines a
Page 59 and 60: 5.5 Routing Module and Classifier O
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Page 63 and 64: $node neighborsThis returns the lis
Page 65 and 66: Linkhead_enqT_queue_ deqT_ link_ tt
Page 67 and 68: 6.2 ConnectorsConnectors, unlink cl
Page 69 and 70: $ns_ link-lossmodel This function
Page 71 and 72: Chapter 7Queue Management and Packe
Page 73: }}}void Queue::resume(){Packet* p =
Page 77 and 78: maxidle_ is the maximum amount of t
Page 79 and 80: dst_ The destination address of pac
Page 81 and 82: 7.5.2 ConfigurationRunning a JoBS s
Page 83 and 84: mean_pkt_size_ Used to set the expe
Page 85 and 86: Demarker objects$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
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Page 103 and 104: hdr_flags* nf = (hdr_flags*)npkt->a
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Page 109 and 110: State Variables are:dupacks_ Number
Page 111 and 112: $agent attach-tbf Attaches a token
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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
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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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}$sizeRNG next-substream# print the
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protected:RNG* rng_;};Classes deriv
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ns-random is implemented in ~ns/mis
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Chapter 26Trace and Monitoring Supp
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The monitor-queue function is const
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also used to accumulate packet drop
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}name,th->size(),flags,iph->flowid(
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PT_TORA,PT_DSR,PT_AODV,// insert ne
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The QueueMonitor class is not deriv
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$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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