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Chapter 14.  Deploying IPv6 in an IP Service Provider Network

Chapter 14.  Deploying IPv6 in an IP Service Provider Network

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NetworkEnvironmentandIPv4Services

RTPComisafictitiouswholesaleaccessproviderthatcovers

mostmajormetropolitanareasintheUnitedStates.Itstarted

byprovidingaccessservicestoitsresidentialandbusiness

customersoverdialupandISDN.Today,mostofitscustomers

areprovidedbroadbandaccessoverxDSL,Fiber,orWiFi.

RTPComprovidesIPv4unicastconnectivityforitscustomers,

linkingthemtotheirInternetserviceprovidersofchoice.

Consideringthelargenumberofresidentialcustomers,

aggregationisimportantinRTPCom'snetworkdesign.Its

backboneisstructuredinthreelevelsofpointsofpresence

(POPs)(Figure14-1).



Figure14-1.RTPComPOPArchitecture



Level1(L1)POPsformthebackboneofthenetwork.They



servicelargemetropolitanareasandtheyprovidetheinterface

tovariousISPs.OriginallytheL1POPswerenotinterconnected

andRTPCom'snetworkwasnotcontiguous.Asitsfootprintand

customerbasegrew,RTPComcouldjustifyowningtheOC-192

linesthatcurrentlyconnectitsL1POPs.

TheL1POPsconnecttoL2(L2)POPsoverOC-192orOC-48

linksdependingonthesizeoftheL2POP.Thelaterprovide

accessservicesinareasofthemetropolitandomainservicedby

theL1POPorinothersmallercities.L2POPsaggregateL3(L3)

POPsoverOC-48orOC-3links.Figure14-2presentsRTPCom's

networkingeographicalcontext.



Figure14-2.RTPComNetworkGeographical

Topology



[Viewfullsizeimage]



ThelinkandmediatypesusedtointerconnectRTPCom'sPOPs

aresummarizedinTable14-1.

Table14-1.BackboneInterfaceTypes

InterfaceType



Speed



Use



OC-192/10Gig



10Gbps



L1-L1andL1-L2POPs



OC-48POS



2.5Gbps



L1-L2andL2-L3POPs



OC-3POS



155Mbps



L2-L3POPs



GigabitEthernet



1Gbps



L1-L3andL2-L3POPs



ThedesignofeachPOPtypeisemphasizingtheneedfor

aggregationandredundancy.Thedifferencesrevolvemainly

aroundthelevelsofaggregationandthebandwidthsofthe

linksused.

TheL1POPsformRTPCom'sbackbonewiththefollowing

characteristics:

Highlysecureoveradedicatedprivatenetwork

Useshigh-bandwidthOC-48andOC-192backbonelinks

Isover-engineered,sothatQoSisnotusedinthecorefor

itsIPv4services

Fullbackboneredundancyusingparallellinksbetweenthe

L1POPs

Usesasingleautonomoussystem



TheyalsocontaintheL2TPNetworkServer(LNS)routersthat

terminatethePPPsessionsinitiatedbythecustomers.ThedeencapsulatedtrafficisthenhandedovertotheISPselectedby

thosecustomers.EachLNSroutersupportsthecustomersofa

singleISPanditconnectsoverdedicatedVLANstotwoedge

routersthatprovidetheuplinktothatISP.TheL1POPdesign

andthebackbonetopologyareshowninFigure14-3.

Authentication,authorization,andaccounting(AAA)resources

thatareusedbytheLNSformanagingthePPPsessionsare

maintainedbythecorrespondingISPandarenotshowninthis

figure.



Figure14-3.Level1POPDesignandBackbone

Topology



AllroutersintheL1POPsbelongtoOSPFarea0.TheL1POPs

peerviaiBGPwiththeL2POPs.AdedicatedIGPisused

betweentheLNSandtheedgerouterstoimplementlayer3

redundancyandloadbalancing.Theedgeroutersconnectto

thecollocatedISProuterswhicharenotshowninthepicture.

MultipleL2POPsaredeployedwithinametropolitanareato

providecustomeraccess.L2POPscanalsobeusedby

themselvesinsmallermarkets.TheyrelyonOC-48Dynamic

PacketTransport(DPT)ringstoaggregatetheaccesslayer

acrossthecoveredareaorL3POPs.Thesamedesignwould

haveappliedtoaResilientPacketRing(RPR,802.17)

infrastructure,too.Figure14-4presentsthestructureofanL2

POP.



Figure14-4.Level2POPDesign



[Viewfullsizeimage]



L2POPspeerviainteriorBorderGatewayProtocol(iBGP)with

theL1POPs.TheyrunOSPFwiththeringinarea0andeach

aggregatedlocation,alocalaccesslayerorL3POPs,connecting

totheringinanareaofitsownasshowninFigure14-4.

ThelastbuildingblockinRTPCom'snetworkdesignpresented

hereistheL3POP.Itservicessmallmarketsorremote

locations.Itisbasicallymadeoftheaccesslayerandan

aggregationlayerthatprovidesconnectivitytoL2POPs(Figure

14-5).



Figure14-5.Level3POPDesign



[Viewfullsizeimage]



L3POPsconnecttoL2POPsoverOC-48orOC-3links.Theyrun

asingle-areaOSPFasanIGP.

TheaccesslayerrepresentedinthePOPdesignfiguresissimilar

forbothL2andL3POPtypes.Itsmaincharacteristicis

scalabilityneededtohandlealargenumberofcustomers

(Figure14-6).



Figure14-6.RTPComAccessLayer



[Viewfullsizeimage]



Intermsofphysicalandlinklayers,RTPComownstheentire

last-mileinfrastructureforallaccesstypesitoffers:ADSL,

FTTH,andWiFi.



Note

RTPComdoesnotofferanyservicesovercable.Ifit

weretoofferservices,extendingIPv6accessover

suchaninfrastructurewouldcomplicatethe

deployment.AsmentionedinChapter3,"Delivering

IPv6UnicastServices,"thecablespecification

(DOCSIS)doesnotsupportIPv6,sotunnelingisthe



onlymechanismavailablefortransportingtheIPv6

traffic.

RTPComiscurrentlyevaluatingWiMAXasanaccess

technologybutnoserviceisyetprovidedasthis

wouldrequirealicensesubscription.



FortheIPv4service,RTPComaggregatesthecustomer-initiated

PPPoverEthernet(PPPoE)sessionsandbundlesthemthrough

Layer2TunnelingProtocol(L2TP)tunnelstotheedgeofits

network.LNSroutersinL1POPsterminatethePPPoEsessions,

de-encapsulatethetraffic,andforwardittoISPs.Theoperation

ofthisserviceisalsoexemplifiedinFigure14-6.

Throughthiswholesalemodel,RTPComisnotresponsiblefor

managingtheglobalIPv4addressesusedbythesecustomers,

becausetheyaremanagedbytheirISP.RTPComonlyprovides

transportfortheencapsulatedtrafficandforthatpurposeit

usestheprivateIPv4addressspace.

ThebulkofRTPCom'sbusinessisprovidingresidential

customerswithaccesstoanISP.Itisalsoaggressively

developingitssmalloffice/homeoffice(SOHO)customerbase.

RTPComwouldliketoexpanditsserviceofferingintotheTriple

Play(data,voice,video)arena.Althoughthewholesalemodel

usedfortheIPv4unicast-basedservicescaneasilysupport

VoiceoverIP(VoIP),itdoesnotsupportinascalablemanner

contentdelivery(CD)-basedonmulticast.AllRTPCom's

customershaveavirtualpoint-to-pointlinktotheirgateway

(LNS)acrossalargeportionofthenetwork(L3,L2,andnearest

L1POP).BecausetheLNSistheonlydevicethatcandotraffic

replicationforalltheendusers,RTPCom'snetworkisflooded

withmultiplereplicasofthesamepacketsforeachcustomer

subscribedtoagivencontentchannel.Thisinefficientuseof



networkresourceslimitssignificantlythescaleofanymulticastbasedservice.



IPv6DeploymentPlans

RTPCom'spursuitofIPv6isnotdrivenbyIPv4address-space

depletionpressures.RTPComreliessafelyontheprivate

addressspacetosupportitswholesalebusinessmodel.Onthe

otherhand,RTPComseesIPv6asanopportunitytocreatethe

next-generationinfrastructurethatwouldallowthecompanyto

increaseitscustomerreach,andmostimportant,todiversifyits

serviceoffering.Inparticular,RTPComintendstoincreaseits

revenuefromexistentbroadbandsubscribersbyprovidingan

infrastructureforvalueaddservicessuchasCD.Itsexpansion

plansinthissensearelimitedbythescalabilityproblemsfaced

withenablingmulticastinitscurrentnetwork.

ThepotentialtoleverageIPv6servicesasservicedifferentiator

inacompetitivemarketdidnotescapeRTPCom'splanning.

Nevertheless,RTPComseesIPv6asanenabler,aswellasan

opportunitytoreinventitsowninfrastructure.



TargetedIPv6Services

Despitedecidingtoexpanditsserviceportfolio,RTPComdoes

notintendtosignificantlychangeitsbusinessmodel.Inother

words,RTPComwillcontinuetobeanaccess,wholesale

providerandwilllinkitscustomerstoservice(Internetor

content)providers.RTPCom'sgoalistoprepareitsnetworkto

supportnewtypesofservicesofferedbytheserviceproviders.

Table14-2summarizestheservicesRTPComcustomerswillbe

abletoreceiveoverIPv4andIPv6.

Table14-2.IPServicesAvailabletoRTPCom's

Customers

ServiceName



IPv4Service



IPv6Service



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Chapter 14.  Deploying IPv6 in an IP Service Provider Network

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