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Chapter 32Hierarchical RoutingThis chapter describes the internals of hierarchical routing implemented in ns. This chapter consists of two sections. In thefirst section we give an overview of hierarchical routing. In the second section we walk through the API’s used for settinghierarchical routing and describe the architecture, internals and code path for hier rtg in the process.The functions and procedures described in this chapter can be found in ~ns/tcl/lib/ns-hiernode.tcl, tcl/lib/ns-address.tcl,tcl/lib/ns-route.tcl and route.cc.32.1 Overview of Hierarchical RoutingHierarchical routing was mainly devised, among other things, to reduce memory requirements of simulations over very largetopologies. A topology is broken down into several layers of hierarchy, thus downsizing the routing table. The table size isreduced from n 2 , for flat routing, to about log n for hierarchical routing. However some overhead costs results as numberof hierarchy levels are increased. Optimum results were found for 3 levels of hierarchy and the current ns implementationsupports upto a maximum of 3 levels of hierarchical routing.To be able to use hierarchical routing for the simulations, we need to define the hierarchy of the topology as well as providethe nodes with hierarchical addressing. In flat routing, every node knows about every other node in the topology, thus resultingin routing table size to the order of n 2 . For hierarchical routing, each node knows only about those nodes in its level. Forall other destinations outside its level it forwards the packets to the border router of its level. Thus the routing table size getsdownsized to the order of about log n.32.2 Usage of Hierarchical routingHierarchical routing requires some additional features and mechanisms for the simualtion. For example, a new node objectcalled HierNode is been defined for hier rtg. Therefore the user must specify hierarchical routing requirements before creatingtopology. This is done as shown below:First, the address format ( ) or the address space used for node and port address, needs to be set in the hierarchical mode. Itmay be done in one of the two ways:set ns [new Simulator]281
$ns set-address-format hierarchicalThis sets the node address space to a 3 level hierarchy assigning 8 bits in each level.or,$ns set-address-format hierarchical ...which creates a node address space for n levels of hierarchy assigning bits as specified for every level.This other than creating a hierarchical address space also sets a flag called EnableHierRt_ and sets the Simulator class variablenode_factory_ to HierNode. Therefore when nodes are created by calling Simulator method “node” as in :$ns node 0.0.1, a HierNode is created with an address of 0.0.1;Class AddrParams is used to store the topology hierarchy like number of levels of hierarchy, number of areas in each levellike number of domains, number of clusters and number of nodes in each cluster.The API for supplying these information to AddrParams is shown below:AddrParams set domain_num_ 2lappend cluster_num 2 2AddrParams set cluster_num_ $cluster_numlappend eilastlevel 2 3 2 3AddrParams set nodes_num_ $eilastlevelThis defines a topology with 2 domains, say D1 and D2 with 2 clusters each (C11 & C12 in D1 and C21 & C22 in D2). Thennumber of nodes in each of these 4 clusters is specified as 2,3,2 and 3 respectively.The default values used by AddrParams provide a topology with a single domain with 4 clusters, with each cluster consistingof 5 nodes.Appropriate mask and shift values are generated by AddrParams for the hierarchical node address space.Each HierNode at the time of its creation calls the method ‘mk-default-classifier ” to setup n numbers of address classifiersfor n levels of hierarchy defined in the topology.HierNode instproc mk-default-classifier$self instvar np_ id_ classifiers_ agents_ dmux_ neighbor_ address_# puts "id=$id_"set levels [AddrParams set hlevel_]for set n 1 $n
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18 Radio Propagation Models 17718.1
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30 Multicast Routing 25130.1 Multic
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38.2.5 An example . . . . . . . . .
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X Other 40347 Educational use of NS
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# so, we lied. now, we define the t
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Chapter 2Undocumented FacilitiesNs
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Part IInterface to the Interpreter1
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• if you can do what you want by
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• tcl.result(const char* s)Pass t
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By convention in ns, the class Agen
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$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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}$sizeRNG next-substream# print the
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protected:RNG* rng_;};Classes deriv
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ns-random is implemented in ~ns/mis
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Page 233 and 234: The monitor-queue function is const
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Page 245 and 246: Chapter 27Test Suite SupportThe ns
Page 247 and 248: ... ...}$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
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Page 281: $ns_ rtmodel This command defines
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Page 289 and 290: Chapter 34TCP AgentsThis section de
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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 319 and 320: same packet. The repair objet does
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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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