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A network simulator is a piece of softwareor hardware that predicts the behavior of anetwork, without an actual network being
present.
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Network simulators serve a variety ofneeds.
Compared to the cost and time involved in
setting up an entire test bed containingmultiple networked computers, routers anddata links, network simulators are relativelyfast and inexpensive
allow engineers to test scenarios that mightbe particularly dicult or expensive toemulate using real hardware
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◦ simulating the eects of a sudden burst in trac
◦ a o! attack on a network service
◦ test new networking protocols or changes toexisting protocols in a controlled and reproducible
environment "ith the help of simulators one can design
hierarchical networks using various types ofnodes like computers, hubs, bridges,
routers, optical cross#connects, multicastrouters, mobile units, $!A%s etc
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&arious types of "ide Area Network '"AN(technologies like )C*, A)$, +* etc and ocalArea Network 'AN( technologies like
-thernet, token rings etc. can all besimulated with a typical simulator
the user can test, analye various standardresults apart from devising some novel
protocol or strategy for routing etc
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a network simulator must enable a user to◦ represent a network topology,◦ specifying the nodes on the network,◦ the links between those nodes◦ and the trac between the nodes
$ore complicated systems may allow the userto specify everything about the protocols usedto handle network trac.
/raphical applications allow users to easilyvisualie the workings of their simulated
environment. )ext#based applications may provide a less
intuitive interface, but may permit moreadvanced forms of customiation.
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0thers, such as /)Nets, are programming#oriented, providing a programmingframework that the user then customies tocreate an application that simulates the
networking environment to be tested.
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Ns1# Command based 0pnet# /raphical 0$N-)22
3ualNet /lomo!im
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0*N-) solutions address application performance management4network planning, engineering, and operations4 and network 56.
0*N-) solutions for Network engineering, operations, andplanning include the following◦ +) /uru Network *lanner helps enterprises plan their network for new
applications or technologies.◦ !* /uru Network *lanner and !* /uru )ransport *lanner optimie
service provider network designs for capacity, cost, 3o!, andsurvivability.
◦ !entinel is 0*N-)7s network con8guration auditing solution and it isused to ensure network integrity, security, and policy compliance.
◦ Net$apper complements 0*N-)7s !entinel and /uru solutions byautomatically creating content#rich network diagrams in $icrosoft &isioformat.
◦ 0*N-) nCompass, a software solution for the N0C, enables operators tovisualie real#time network topology, trac, events, and status in asingle view.
0*N-) $odeler, a network modeling and simulation softwaresolution, is one of 0*N-)7s 9agship solutions and also its oldestproduct
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Global Mobile Information SystemSimulator '/lo$o!im( is a network protocolsimulation software that simulates wirelessand wired network systems.
/lo$o!im is designed using the paralleldiscrete event simulation capability providedby Parsec, a parallel programming language.
/lo$o!im currently supports protocols for a
purely wireless network. +t uses the *arsec compiler to compile thesimulation protocols.
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ns was built in C22 and provides a simulationinterface through 0)cl, an ob:ect#oriented dialectof )cl.
)he user describes a network topology by
writing 0)cl scripts, and then the main nsprogram simulates that topology with speci8edparameters.
)he N!1 makes use of 9at earth model in whichit assumes that the environment is 9at without
any elevations or depressions. ;owever the realworld does have geographical features likevalleys and mountains. N!1 fails to capture thismodel in it.