InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 159 ComparativeAnalysis of Link State Routing ProtocolsOPSF and IS-IS Amanpreet Kaur [1], Er.Dinesh Kumar [2] Department of Computer Science and Engineering GZS PTU Campus, Bathinda Punjab - India ABSTRACT IPRoutingisusedtofindthebestpathforanIPpacketfromsource to destination. Major routing protocols used for interior gateway routing are link state routing protocols, as they are more scalable than their counterparts Distance Vector RoutingProtocols. Link State routing protocols has two protocols listed in its category and both of them uses the same Dijkstra'sShortestPathFirstAlgorithm,andbothcametoexistenceataboutsametime.Butwhichprotocolisbest between the two always creates confusion in the network engineers minds all around the world. This paper explains the twolinkstaterouting protocols used for internal routing purposes in enterprise or service provider networks. Link state routing protocols use the same algorithm but have so many differences. This paper compares both the link state routing protocols on the basis of performance, security and scalability.Keywords:-IP, OSPF, IPv6,LSA,PDU,LSU,LSR,IS-IS I.INTRODUCTION Whenadatagramissentbetweensource and destination devicesthatareonthedifferentnetworks,theprocessis known as routing. For IP routing, two types of methods can beused,eitherwecanuseStaticRoutingorwecanuse DynamicRouting.Instaticrouting,weaddtheroutes towardsdestinationmanuallyandindynamicrouting,we usedynamicroutingprotocolsthatfindthebestpath towardsdestinationdynamically.Dynamicrouting protocolsarefurtherdividedintotwocategoriesi.e. InteriorGatewayProtocols(IGP)andExteriorGatewayProtocols(EGP).EGPsareusedwhenweneedtoconnect withsome other routing domain, currently Border Gateway Protocolisthe only EGP in the world. IGPs are used when weneedtoperformroutingondifferentrouterswithina singleroutingdomain.IGPsarefurtherdividedintotwo types:DistanceVectorRoutingProtocols-Basedon distanceanddirection.RoutingInformation Protocol(RIP),EnhancedInteriorGatewayRouting Protocol(EIGRP)andLinkState Routing Protocols. As our mainemphasisisonLinkStateRoutingProtocols, therefore they are described in the next section. A.Link State protocols LinkStateprotocols,alsoknownasshortestpathfirstor distributeddatabaseprotocols,arebuiltaroundawell-knownalgorithmofgraphtheory,E.W.Dijkstra's shortest path first algorithm.LinkState protocols behave like a road map.Eachroutersharesitslinkinformation in the form of LinkStateAdvertisement(LSA),orLinkStatePDU(LSP). Alinkstaterouteruseslinkstateinformationtocreatea topology map and to select the best path to the destination in the topology. LSAs propagates to every neighbor router usingprotocolspecificmulticastaddress, each router that receivestheLSA,updatesitsLink-State-Database(LSDB) andforwardstheLSAtoitsneighborrouterswithinan area.SPFtree is then applied to the LSDB to find the best path to reach the destination and the best path is then added to the routing table. DijkstraAlgorithmis given: Dijkstra() {//Initialization Path={s}//s means self for ( i = 1 to N ) { If (I is a neighbor of s andI s ) Di = Csi If (I is a not aneighbor of s )Di = } Ds= 0 RESEARCHARTICLEOPENACCESS InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 160 }// Dijkstra //Iteration Repeat { // Findingthe next nodetobe added Path=PathiifDiisminimumamongallremaning nodes // Updatethe shortest distanceforthe rest For(j=1to M)//M numberof remainingnodes { Dj = minimum(Dj,Dj+ cij) } until (allnodes include in the path , M = 0) LinkState Routing Protocol includes - B.Open Shortest Path First(OSPF) OSPFisaroutingprotocol,whichisdeployedinboth enterpriseandserviceprovidernetworks.Networkis dividedintoareas.Area0isknown as backbone area, for everyother area0 connect with any other area except area 0,theyhavetoreachviaarea0astransitarea.OSPF behaveslikeadistancevectorroutingprotocolwhen sharing routes from one area to other area. OSPF uses Link StateAdvertisements(LSAs)toshareinformation regardingroutesinthenetwork.Figures howingbasic OSPFimplementationis shown below: Figure 1:Basic OSPFImplementation C.I ntermediate-System-to-I ntermediate-System(I S-I S) ItisalinkstateprotocolsimilartoOSPF,usedin core of SPnetworks.Itwasoriginallynot an IP protocol, and is a partofCLNSstack,IntegratedIS-ISisanIPextension of IS-IS.Itishighlyscalableandhaveasimpleflatnetwork design. It supports both IPv4 and IPv6. IS-IS use Dijkstra's SPFalgorithmtofindthebestpath.IS-ISalsousesa differentaddressingformatthanofOSPF.ItusesISO NSAPAddressingformat,whosemaximumsizeis20 bytesand minimum size of 8 bytes. It uses two "levels" of adjacency - Level2(L2)and Level 1(L1). Figure2:Basic Integrated IS-IS implementation. II.LITERATURESURVEY OSPFVersion2[1]byJ.MoyinInternetEngineering TaskForce(IETF)RFC-2328documentsversion2ofthe OSPFprotocol.Thisdocumentrepresentsinternational standard document used for OSPF. It is designed to be run internal to a single Autonomous System. Each OSPF router maintains an identical database describing the Autonomous System'stopology.Fromthisdatabase,aroutingtableis calculatedbyconstructingashortestpath tree. IETF RFC 2328isthestandardinuseforIPv4OSPFdesignand implementation. TheOSPFNot-So-StubbyArea(NSSA)Option[2]byP. MurphyofUSGeologicalSurveyinIETFRFC3101 documentsanoptionaltypeofOpenShortestPath First(OSPF) area that is referredto as "not-so-stubby" area (orNSSA).NSSAsaresimilartotheexistingOPSFstub area configuration option but have the additional capability ofimportingASexternalroutesin a limited fashion. OSPF NSSAoptionwasoriginallydefinedinIETFRFC1587. RFC3101isthecurrentdocumentusedinNSSA implementation. GracefulOSPFRestart[3]byJ.MoyofSycamore Networks,P.Pillay-EsnaultofJuniperNetworksandA. LindemofRedbackNetworksinIETFRFC3623 InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 161 documentsanenhancementto the OSPF routing protocol, wherebyanOSPFroutercanstayonthe forwarding path evenasitsOPSFsoftwareisrestarted.Thisis called"gracefulrestart"or"non-stopforwarding".A restartingroutermaynotbecapableofadjustingits forwardinginatimelymanner when the network topology changes.Inordertoavoidthepossibleresultingrouting loops,theprocedurein this memo automatically reverts to anormalOSPFrestartwhensuchatopologychangeis detected,orwhenoneormoreoftherestartingrouter's neighborsdo not support the enhancements in this memo.Propernetworkoperationduringagracefulrestartmakes assumptionsupontheoperatingenvironmentofthe restarting router; these assumptions are also documented. RoutingExtensionsforDiscoveryofMultiprotocol (MPLS)LabelSwitchRouter(LSR)TrafficEngineering (TE)MeshMembership[4]byS.YasukawaofNTT,S. Previdi,P.PsenakofCiscoSystemsandP.Mabbeyof ComcastinIETFRFC4972specifiesthesetupofafull meshofMulti-ProtocolLabelSwitching(MPLS)Traffic Engineering(TE)LabelSwitchedPaths(LSP)amongaset ofLabelSwitchRouters(LSR),whichisacommon deploymentscenarioofMPLSTrafficEngineeringeither forbandwidthoptimization,bandwidthguaranteesorfast reroutingwithMPLSFastReroute.Suchdeployment may requiretheconfigurationofapotentiallylargenumberof TELSPs. OSPFforIPv6[5]byR.ColtunofAcoustraProductions, D.FergusonofJuniperNetworks,J.MoyofSycamore NetworksandA.Lindem,EdofRedbackNetworksin IETFRFC5340describesthemodificationstoOSPFto supportversion6 of the Internet Protocol (IPv6). Changes between(OSPFforIPv4,OPSFv2)and(OSPFforIPv6, OSPFv3)aredescribedinthisdocument.Addressing semanticshavebeenremovedfrom OSPF packets and the basicLinkStateAdvertisements(LSAs).NewLSAshave beencreatedtocarryIPv6addressesandprefixes.OSPF now runs on a per-link basis rather than on a per-IP-subnet basis.FloodingscopeforLSAshasbeengeneralized. Authenticationhasbeenremoved from the OSPF protocol andinsteadreliesonIPv6'sAuthenticationHeaderand Encapsulating Security Payload.OSPFv3GracefulRestart[6]byP.Pillay-EsnaultofCisco SystemsandA.LindemofRedbackNetworksinIETF RFC5187describestheOSPFv3gracefulrestart.The OSPFv3gracefulrestartisidenticaltothatofOSPFv2 exceptforthedifferencesdescribedinthisdocument.ThesedifferencesincludetheformatofthegraceLink State Advertisements (LSAs) and other considerations. TrafficEngineeringExtensionstoOSPFVersion3[7]by K.Ishiguro,V.ManralofIPInfusion,A.DaveyofData ConnectionLimitedandA.Lindem,Ed.ofRedback NetworksinIETFRFC5329describesextensionsto OSPFv3tosupportintra-areaTrafficEngineering(TE).ThisdocumentextendsOSPFv2TEtohandleIPv6 networks.AnewTLVandseveralnewsub-TLVsare defined to support IPv6 networks. OSPFExtensionsinSupportof Inter-Autonomous System (AS)MPLSandGMPLSTrafficEngineering[8]byM. Chen,R.ZhangofHuaweiTechnologies,X.Duanof ChinaMobileinIETFRFC5392describesextensionsto theOSPFversion2and3protocolstosupport MultiprotocolLabelSwitching(MPLS)andGeneralized MPLS(GMPLS)TrafficEngineering(TE)formultiple AutonomousSystems(ASes).OSPF-TEv2andv3 extensionsaredefinedforthefloodingofTEinformation aboutinter-ASlinksthatcanbeused to perform inter-AS TEpath computation. OSIIS-ISIntra-domainRoutingProtocol [9] by D. Oran of DigitalEquipmentCorporationinIETFRFC1142isa republicationofISO DP 10589 as a service to theInternet community. UseofOSIIS-ISforRoutinginTCP/IPandDual Environments[10]byR.CallonofDigitalEquipment CorporationinIETFRFC1195specifiesanintegrated routingprotocol,basedontheOSIIntra-DomainIS-IS RoutingProtocol,whichmaybeusedasaninterior gatewayprotocol(IGP)tosupportTCP/IPaswell as OSI. This allows a single routing protocol to be used to support pureIPenvironments,pureOSIenvironments,anddual environments. This specification was developed by the IS-IS workinggroup of the Internet Engineering Task Force. RestartSignalingforIS-IS[12]byM.Shandand L.GinsbergofCiscoSystemsinIETFRFC5306describes amechanismforarestartingroutertosignaltoits neighborsthatit is restarting, allowing them to reestablish theiradjacencieswithoutcyclingthroughthedown state, whilestillcorrectlyinitiatingdatabasesynchronization. Thisdocumentadditionallydescribesamechanismfora restartingroutertodeterminewhenithasachievedLink StateProtocolDataUnit(LSP)databasesynchronization withitsneighborsandamechanismtooptimizeLSP databasesynchronization,whileminimizingtransient routing disruption when a router starts. InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 162 IS-ISExtensionsforTrafficEngineering[13]byT.Liof RedbackNetworksinIETF RFC 5305 describes extensions totheIntermediateSystemtoIntermediateSystem(IS-IS) protocoltosupportTrafficEngineering(TE).This documentextendstheIS-ISprotocolbyspecifyingnew informationthatanIntermediateSystem (router) can place inLinkStateProtocolDataUnits(LSP). This information describesadditionaldetailsregardingthestateofthe networkthatareusefulfortrafficengineering computations. Routing IPv6 with IS-IS[14] by C. Hopps of Cisco Systems inIETFRFC5308specifiesamethodfor exchanging IPv6 routinginformationusingtheIS-ISroutingprotocol.The describedmethodutilizestwonewTLVs:areachability TLVandaninterfaceaddressTLVtodistributethe necessaryIPv6informationthroughoutaroutingdomain.Using this method, one can route IPv6 along with IPv4 and OSIusing a single intra-domainrouting protocol. IPv6TrafficEngineeringinIS-IS[15]byJ.Harrison,J. BergerandM.BarlettofMetaswitchNetworksinIETF RFC6119specifiesamethodforexchangingIPv6traffic engineeringinformationusingtheIS-ISroutingprotocol. ThisinformationenablesroutersinanIS-ISnetworkto calculate traffic-engineeredroutes using IPv6 addresses. OSPFandIS-IS:AComparativeAnatomy[16]byDave Katz,ofJuniperNetworksdoesacomparativeanalysis of OSPFand IS-ISprotocol. III. PROBLEM DEFINITION Asstatedinthe Introduction part of thisdocument, when IETFwastochoosebetweenOSPFandIS-ISrouting protocoltomakethemasthestandardInteriorGateway RoutingProtocoloftheinternet,theyleftthatto Internet Service Providers and Enterprise Networks by making both protocols as standards and let the ISP and Enterprise select which routing protocol they want to use.Therearenoperfectdocumentationonwhichisthe better routing protocol of the two. ISO engineers say that ISIS is best, while according to IETFengineers, OSPFis the best.Both protocols use the same algorithm, yet they are so different. IV.OBJECTIVE To find the best link-state routing protocol on the basis of performance,security, scalability,and usage of CPUresources. To find the best link-state routing protocol for service provider networks for their core network. V.RESULTS A.PerformanceAnalysisofOSPFandI SI S protocol using default parameters OSPFandIS-ISbothdefinetheirnetworkwithinareas. OSPFhasabackboneareai.e.Area0.0.0.0orArea0.In OSPF,thereis a prerequisite for every non-backbone area, thatinorderforanon-backbonearea to connect or share routes with any other non-backbone area, there has to be a backbone area as a transit point in between them. Without Area0inbetweentwonon-backboneareas by default do not share their routes. OSPF topology can be either single-areaormultiple-area.AsingleareaOSPFdesignisshow below. Figure 3-OSPFand ISIS design IntheaboveOSPFsingle area network design, six routers areusedandallareinthesameareai.e.Area0,andthe cloud C1 is our Laptop's loopback address used to connect PRTGTrafficAnalyzerandMonitoringToolwithour topology.HerewewillmonitorR6'sloopbackaddress 6.6.6.6withPRTG,whichwillsendasimplepingto 6.6.6.6everysecondtomonitoritsperformanceand availability.We have two paths towards destination and the bestpathisviaR1-R2-R3-R6-6.6.6.6,Followinggraphin Figure 1.2 will show the amount of timethat the link takes toconvergeifthebestlinkto6.6.6.6isfailed.Graph shown below is taken without tuning any OSPF timers and LSApacingmechanism,alsonootherfaster convergence mechanismlikeBi-directionalForwardingDetection (BFD)orSPFThrottlingis used : InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 163 Figure4-PRTG Graph shows the amount of time it takes to converge the link fromprimaryto secondary link Intheabovegraphcreatedfrom PRTG Traffic Monitoring Tool,amountoftime(minimumormaximum)inmsecis shownforapacket to reach destination is also shown. Its clearfromtheabovePRTGgeneratedgraphthatOSPF takesaround5secondstoconvergefromprimaryto backuplink,iftheprimarylinkgoesdown.Intheabove topology we have not used any faster convergence protocol likeBidirectionalForwardingDetectionorFastRouting ConvergencemethodlikeThrottlingShortestPath First(SPF)timers. IS-ISontheotherhandisalsousedinserviceprovider networksfortheirinternalnetworks.Thereisalwaysa debate regarding the best interior gateway routing protocol in service provider networks. OSPF and ISIS have so many similarities as both are link-state routing protocols and uses thesameShortestPathFirst(SPF)algorithm,yettheyare sodifferentasoneofthemis used is IP based, and other one is created for ISO CLNS environments and then it was adoptedbyIETFandnamed it Integrated IS-IS. Topology that we used is show below : Figure 5 - Integrated IS-ISSingle Area Topology IS-ISisconceptuallysimilartoOSPFinsomanyways, originallydevelopedbyISO,ISISreferredarouterasan IS(IntermediateSystem)andahostorendsystemasan ES(EndSystem). IntheaboveIS-ISnetworkdesign,alltherouterscome underthesameIS-ISarea,withR1-R2-R3-R4-4.4.4.4as theprimarylinkandR1-R6-R5-R4-4.4.4.4assecondary linkwith4.4.4.4isconnectedwithR4.Theconvergence time in IS-IS with default setting without tuning any timers orchanginganyotherparametersisshow below with the help of a graph created in PRTGtrafficmonitoring tool : Figure 6-IS-ISConvergence timegraph in PRTG Now as shown above, IS-IS gives much lesser downtime as compared to OSPF. IS-IS,whenusesameareaforitsentirenetworkhasa muchlesserconvergencetimebydefault,i.e.3seconds. IS-ISprotocolsupportsatwolevelhierarchytoscale routinginlargenetworks.Tablebelowdisplaysdefault convergence difference between ISISand OSPF. TABLE1-DefaultconvergencedifferencebetweenISIS and OSPF ProtocolConvergenceTime OSPF5 seconds Integrated IS-IS3 seconds As we can see in the above table, 5 seconds and 3 seconds arethedefaultconvergencetimethatOSPF and IS-IS can take,incaseiftheprimarylinkgoesdownand convergenceneedstohappentowardsBackupLink. Defaultconvergencetimeiswaytoomuchfortoday's networks, but we can shorten the times by using techniques likedecreasingthehelloandSPFcalculationtimersof protocolsorwecanalsouseBidirectionalForwarding DetectionfeaturewithOSPFandISIS,whichcanprovide sub-secondconvergencefromprimarytobackuplinkin case of primarylinkfailure. AsbothOSPFandIS-ISroutingprotocolsusethesame Dijkstra's Shortest Path First(SPF) algorithm, i have tries to fastentheSPFcalculationsinordertocheckwhateffect does it make to the convergence time.What i have done is, ichangedthe"DelaybetweenreceivingachangetoSPF InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 164 calculationto100msec","Delaybetweenfirstand second SPFcalculationto100msec"and"Maximumwaittimefor SPFcalculationsto120msec".The result after configuring SPFtimers is shown below in a graph : Figure 7-Convergence Time after fasten the process of SPF calculationAswecanseefromtheabovegraph,aftertuningSPF timers,convergencetimehasdecreasedtosub-second, which is much betterthan the default timers. Both ISIS and OSPFcangivesub-secondconvergenceaftertuningSPF timers. TABLE2-SPFfast convergence between ISIS and OSPF: ProtocolConvergence Time(Default Parameters) Convergence Time(WithSPF timers tuned) OSPF5Sub-Second ISIS3Sub-Second B.Performance Analysis of Link State Routing Protocols using I Pv6 OSPFandISIS,bothcanruninIPv4andIPv6 environments,OSPFwhenusedwithIPv6isknownas OSPFv3andisquitedifferentthanOSPFv2.Ihavealso used OSPFv3 for performance analysis. Topology used for OSPFv3performance analysis is shown below: Figure 8-OSPFv3topology used for Performance AnalysisAbove topology is used for OSPFv3 performance analysis, cloudshowninabovediagramisactingasaPChaving PRTGinstalled and is testing the reachability towards R4's loopbackaddress2010::1 address. In the topology, R1 has two paths to reach R4, one via R2 and R3 and the other one viaR5andR6,Bydefaultthe best path is decided on the basis of cost from source to destination, path with the least costbecomesthebestpathtowardsdestination,iftwo paths have same cost from source to destination, then both entersintoroutingtable.Inourcase,trafficisgoing throughR2andR3whichis the better link with the better cost,butwhenthelinkbetweenR2andR3goesdown, how fast does the network converge is shown in the graph below: Figure9-Graphshowingthemaximum,minimumand convergence time in OSPFv3implementationusing PRTG Ontheotherhand,wheniuseISISwithIPv6,itismuch easiertoimplement,asithasthesameversionforboth IPv4andIPv6.TopologyusedforISISwithIPv6is same asintheOSPFv3withjustroutingprotocolischanged fromOSPFv3toISIS.IPv6addressingisusedisstillthe same.ResultstakenfromtheISISwithIPv6topologyin case of primarylinkfailureis shown below: Figure10-Graphshowingthemaximum,minimumand convergencetimeinISISwithIPv6implementationusing PRTG InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 165 Astheabove graph shows, the maximum time to complete asimplepingpacketis183msec,minimumtimeis49msec andtheconvergencetimebetweenthe primary link failure andtrafficshiftfromprimarylink towards backup link is 5 seconds.Therefore with default parameters, ISIS with IPv6 isagainbetterthanOSPFv3.Tablebelowshowsthe comparisonofconvergencetimes of both OSPFv3 and IS-IS with IPv6. TABLE3-ConvergencebetweenOSPFv3andISISwith IPv6. ProtocolConvergenceTime OpenShortestPath First-Version3 (OSPFv3) 7 seconds Intermediate-Systemto Intermediate-System withIpv6(ISISwith IPv6) 5 seconds C.Security Analysis of Link State Routing Protocols: SecurityisalwaysoneofthemajorconcernsofNetwork Industry.Bydefaultroutingprotocolssharerouting informationwiththeirneighborroutersinaveryinsecure manner.We can use passwords for neighbor authentication, sothatroutingprotocolscansharetheirrouting informationonlyiftheirpasswordsmatch.Ihaveused neighborauthenticationwithboththelinkstaterouting protocolandcapturedtheOSPFandISISpacketsin WiresharkPacketSniffertogathersomemore information regardingtheauthenticationinordertocompareboth authentication mechanisms. 1)I S-I S Neighbor AuthenticationISISsupportsbothclear-textandMD5based authentication.InISIS,wecanapplyauthenticationon threelevels:betweenrouters,area-wide(Level1),and Domain-wide(Level2).Authenticationis always configured separately for L1 and L2 adjacencies.If no level is defined duringauthenticationprocess,thenauthenticationis appliedtobothL1andL2levels.AuthenticationinISIS authenticatestheHelloProtocolDataUnits(PDUs).ISIS useskey-chainmechanismforpasswordauthentication whichisusedmainlytoconfiguremultiplepasswords according to time. Figure11-WiresharkCaptureofaHelloProtocolData Unit with authentication applied. AbovecaptureinWiresharkshows the Hello PDU in ISIS protocol,Italsodisplaystheneighborauthenticationis used with MD5 hashing algorithm is in use. 2)OSPF Neighbor Authentication InOSPF,authenticationcanbeconfiguredintwoways; eitheritcan be for area or for specific neighbor connected with some interface. If area based authentication is applied, thenitmustbeconfiguredfortheentirearea,while interface passwords need not to be matched on entire area. OSPFsupportsthreeauthenticationtypes:Null Authentication,ClearText Passwords, MD5 cryptographic checksums.Authentication keys are locally significant to an interfacein case of interface based passwords, and can be different on a per interface basis. Figure12-WiresharkcaptureofOSPFHellopacket showing Authentication Applied. 3)Link State Routing Protocols with I PSec Applied IPSECisaprotocolsuiteoracollectionofprotocols and algorithmstoprotectIPpacketsatLayer3,whichisthe reason,itsalsoknownasIPSecurityorIPSec.IPSec InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 166 provides the benefits of confidentiality through encryption, dataintegritythroughhashingandhmac,and authentication using pre-shared keys and digital signatures. Apartfromthese,IPSec also provides anti-replay support. AgraphbelowshowstheIPtrafficfromsourceto destinationsandpacketswhichareencryptedand decrypted.BelowgraphistakenfromCiscoConfiguration Professional. Figure13-GraphsshowingEncryptedandDecryptedIP traffic. D.Scalability Analysis of OSPF and I S-I S ProtocolLarge Internet Service Provider networks can be created by buildingalargeLevel-1(L1)areawithoutaddingany hierarchiesinIS-ISanditcanstillworkinbettermanner thanifOSPFhasalargenumberofrouterspresentina single area. Inter-Area traffic engineering has lots of issues and is not easy to manage, therefore most service providers prefer to use single area design which can be much easy to manage.WithISIS,bignetworkscanbemadewithout havinghierarchicaldesign as all IP prefixes are considered asleafnodesin the Shortest Path First for IS-IS. The best thingwithSPFinISISisthatfullSPFcalculationisnot triggered for an interface or a route flapping instance, while OSPFdoesfull SPF calculation every time any information changes.GraphbelowshowsrisingCPUutilizationwith ISISand OSPF: Figure 14- ISISScalabilitygraph withrising traffic. Figure 15-OSPFscalability graph with rising traffic TABLE4-PerformanceTableofLinkStateRouting Protocols Protocol Convergence Time ConvergenceTime withSPF Timers Open Shortest Path First v2 5 secondsSub-Second Intermediate-Systemto Intermediate-System 3 secondsSub-Second Open Shortest Path First-Version 3 (OSPFv3) 7 seconds1.5-2seconds Intermediate-Systemto Intermediate-Systemwith Ipv6(ISIS with IPv6) 5 secondsSub-Second VI.CONCLUSIONAND FUTURE SCOPE OSPFandISIS,bothusethesamealgorithmtofindthe bestpath.ISISbehavesmuchbetterwithdefault parameters,and converges the network in 3 seconds while OSPFtakesaround5seconds.WhenSPFtimersare decreasedtomillisecondsthentheconvergencetime also decreasedtosub-secondforbothprotocols.Forsecurity analysis,neighborauthenticationpasswordsforsecure sharingofIPpacketsbetweenboththerouting protocolshaveused.OSPFandISISbothusesMD5hashing technique but ISIS has the ability to use the key-chain, with InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 167 which we can create multiple passwords according to time, whileOSPFusesinterfaceorareabasedpasswords.To secureIProutingprocessofOSPF and ISIS, IPSec is also used,whichprovidesencryption,hashing,authentication features to both the protocols providing them security over Publicnetworkslikeinternet.Inscalabilityperspective, ISISbehavesbetterthanOSPFinlargerServiceProvider Networks,asitcanhavea large single area and it does n't run full SPF calculation when some route flaps, therefore it straightwayresultsinlesserconsumptionofCPU resources.AlsoISISusesTLVformat,withwhichifwe wanttoadd some new feature, it can be easily added with new TLV,which is not the case with OSPF. OSPFandISISarethepioneerIGPsusedinService ProviderIndustryfortheirCoreNetworks.LinkState routingprotocolsare improving with the time. With all the IPtrafficincreasingatratehigherthan ever, there needed tobe some improvements needed in terms of scalability as theserviceproviderandenterpriserouterswillgetmore routingtrafficthanbeforeanditcanonlyincreasewith timethereforethereisneedofmoreefficiencyinLink State Routing Protocols. ACKNOWLEDGMENT Thispaperhasbeenmadepossiblethroughtheconstant efforts and help from my parents and guide. I would like to thankAssosiateProf.Er.DineshKumar, for his guidance, help and valuable suggestions. REFERENCES [1]OSPFVersion2byJ.MoyinInternetEngineering Task Force(IETF)RFC- 2328 [2]TheOSPFNot-So-StubbyArea(NSSA)Option by P.MurphyofUSGeologicalSurveyinIETFRFC 3101 [3]GracefulOSPFRestartbyJ.MoyofSycamore Networks,P.Pillay-EsnaultofJuniperNetworks andA.LindemofRedbackNetworksinIETFRFC 3623 [4]RoutingExtensionsforDiscoveryofMultiprotocol (MPLS)LabelSwitchRouter(LSR)Traffic Engineering(TE)MeshMembershipbyS. YasukawaofNTT,S.Previdi,P.PsenakofCisco SystemsandP.MabbeyofComcastinIETFRFC 4972 [5]OSPF for IPv6 by R. Coltun of Acoustra Productions, D.FergusonofJuniperNetworks,J.Moyof SycamoreNetworksandA.Lindem,Edof Redback Networks in IETFRFC5340 [6]OSPFv3GracefulRestartbyP.Pillay-Esnaultof Cisco Systems and A. Lindem of Redback Networks in IETFRFC5187 [7]TrafficEngineeringExtensionstoOSPFVersion3 [7]byK.Ishiguro,V.ManralofIPInfusion,A. DaveyofDataConnectionLimitedandA.Lindem, Ed. of Redback Networks in IETFRFC5329 [8]OSPFExtensionsinSupportofInter-Autonomous System(AS)MPLSandGMPLSTraffic EngineeringbyM.Chen,R.ZhangofHuawei Technologies,X.DuanofChinaMobileinIETF RFC5392 [9]OSIIS-ISIntra-domainRoutingProtocolbyD.Oran ofDigitalEquipmentCorporationinIETFRFC 1142 [10]UseofOSIIS-ISforRoutinginTCP/IPandDual EnvironmentsbyR.CallonofDigitalEquipment Corporation in IETFRFC1195 [11]RoutingExtensionsforDiscoveryofMultiprotocol (MPLS)LabelSwitchRouter(LSR)Traffic Engineering(TE)MeshMembershipbyJP. Vasseur,Ed.,S.Previdi,P.PsenakofCisco Systems,JL.Leroux,Ed.ofFranceTelecom,S. YasukawaofNTT,andP.MabbeyofComcastin IETFRFC4972 [12]RestartSignalingforIS-ISbyM.Shandand L.Ginsbergof Cisco Systems in IETFRFC5306 [13]IS-ISExtensionsforTrafficEngineeringbyT.Li of Redback Networks in IETFRFC5305 [14]RoutingIPv6withIS-ISbyC.HoppsofCisco Systems in IETFRFC5308 [15]IPv6TrafficEngineeringinIS-ISbyJ.Harrison,J. BergerandM.BarlettofMetaswitchNetworksin IETFRFC6119 [16]OSPFandIS-IS:AComparativeAnatomybyDave Katz,ofJuniperNetworks- http://www.nanog.org/meetings/nanog19/presentations/katz.ppt InternationalJournal of ComputerScienceTrendsand Technology(IJCST) Volume3 Issue 4,Jul-Aug 2015 ISSN: 2347-8578www.ijcstjournal.org Page 168 [17]CiscoOSPFConfigurationGuide- http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/12-4t/iro-12-4t-book/iro-cfg.html [18]CiscoIS-ISforIPConfigurationGuide- http://www.cisco.com/c/en/us/td/docs/ios -xml/ios/iproute_isis/configuration/15-mt/irs-15-mt-book/is-is_overview_and_basic_configuration.html