network sdh_optical protection

5 NetworkSurvivabilityy

AgendaAgenda BasicConcepts ProtectioninSONET/SDH ProtectioninIPNetworks ProtectioninOpticalLayer InterworkingbetweenLayers Summary

6.1BasicConcepts6.1BasicConcepts

BasicConception

NetworkSurvibabilityWhat?

Theabilityofcontinueprovidingservicesinthepresentoffailures,commonlysupplying99.999%availabilityofthenetwork

Why?

Millionsofuserscanbedisruptedandmillionsofdollarscanbelostforsomenetworkrelatedoutageg

How?

Providingredundantcapacityandautomaticallyreroutingtraffic

BasicConcepts Distinguishsomeprotection()schemes

DedicatedorSharedAssignmentofprotectionbandwidthonetoone ormultipletoone. Revertiveornonrevertiveswitchingbackornotafterthefailureisrepaired.DedicatedprotectionmaybeRevertiveornonrevertivewhereassharedmustbeRevertive. Unidirectional switching and bidirectional switching Unidirectionalswitchingandbidirectionalswitching(seenext)

( ) working

Basic Concepts

(a)

(b)Source

Dest.Source

Dest.

working

workingprotect

protect

traffic

no traffic

Figure10.1(a)Unidiretionalprotectionswitching(b)Bidiretionalprotectionswitching

p

BasicConcepts

How the traffic is rerouted in case of a failureHowthetrafficisreroutedincaseofafailurePathswitchingSpanswitchingRingswitching

Differentprotectionschemesoperateatdifferentlayersinthenetworkandatdifferentsublayerswithinalayer.

BasicConcepts

( ) (b)

Normal connection Path switching

(a) (b)

(c) (d)

Span switching Ring switching

(c) (d)

Figure 10.2 switching schemes

6.2Protectionin6.2ProtectioninSONET/SDHSONET/SDH

ProtectionSchemesinSONETandSDH

SONETandSDHhavethesimilarprotectionh diff t l tschemes,differentnomenclatures

Eachprotectionschemeassociatedwithaspecificlayerinthenetwork

SummaryofprotectionschemesinSONETandSDH

SONET Term 1+1 1:N UPSR BLSRSDH Term

TypeTopologyLayer

1+1 1:N SNCP MS-SPRing

Dedicated Dedicated DedicatedShared SharedPoint-point Point-point Ring RingRing/meshLine/MS Line/MS Line/MSPath/- -/Path


Notes:Notes:N:numberofworkinginterfacesharingasingle

protectioninterfaceUPSR:UnidirectionalPathSwitchedRingschemeSNCP:1+1SubNetworkConnectionProtectionBLSR:BidirectionalLineSwitchedRingMSSPRing : Multiplexed SectionShared ProtectionMS SPRing:MultiplexedSection SharedProtection

Ring


Restoration time ( Restorationtime(InSONET/SDHstandards,servicemustbewithin

60ms detect the failure(10ms)

signal to other nodes,including propagation delay

actual switching timerestoration

actual switching time

reacquire the frame synchronization after the switch-over has occurred

time

PointtoPointLinks

1+1protectionTraffic is transmitted simultaneously on working andTrafficistransmittedsimultaneouslyonworkingandprotectionfibersfromsourcetodestination.Whenworkingfiberiscut,thedestinationswitchesovertotheotherfibertoreceivedata.

1:1protection,1:NprotectionTrafficistransmittedoveronlytheworkingfiber,when

kiworkingfiberiscut,bothsourceanddestinationswitchovertotheprotectionfiber.

PointtoPointLinks

splitter switch

switch

switch

switch

switch

(a)

(b)

switch

switchswitch

switchLow-priority data

(c)

Figure 10.3 1+1,1:1,1:N protection

PointtoPointLinks

Comparison of 1+1 and 1:1 protectionComparisonof1+1and1:1protection 1+1protectionisfasterandrequiresnosignalingprotocol,while1:1needsprotocol

Protectionfiberin1:1schemecantransmitlowerprioritytrafficundernormaloperation

1:1protectioncanbeextendedtoshareasingleprotectionfiberamongmanyworkingfibers(1:N)

SelfHealingRings

Concept of ringConceptofringSimplesttopologythatis2connected

SelfhealingRingsRingscanautomaticallydetectfailuresandreroutetraffic

awayfromfailedlinksornodesontootherroutesrapidlyroutes rapidly

Ringarchitectureswidelydeployed Twofiberunidirectionalpathswitchedrings(UPSR) Fourfiberbidirectionallineswitchedrings(BLSR/4) Twofiberbidirectionallineswitchedrings(BLSR/2)

UnidirectionalPathSwitchedRings

WorkingconnectionAtoBg

ADM A

B

C ADM

ADM working connection B to A

protect connection B to A

protect connection protection fiber

path

ADMD

protect connection A to B

protection fiber

working fiber

Figure 10.4 UPSR


1+1 scheme operating at the path layer1+1schemeoperatingatthepathlayer Easilyhandlefailuresoflinks,nodes Simpletoimplement,thus,lowcost requiringnoprotocolandcommunicationbetween

nodes,thus,shortrestorationtime Drawback:lowfiberutilization Popularlyusedinlowerspeedlocalexchangeandaccess

networks


Limit on the number of nodes or ring lengthLimitonthenumberofnodesorringlengthLimitedbyrestorationtimeaffectedbythedifferentdelaysassociatedwiththeclockwiseandcouterclockwisepathtakenbyasignal

BidirectionalLineSwitchedRings

Operating at the line layer (SONET) or multiplexOperatingatthelinelayer(SONET)ormultiplexsectionlayer(SDH)

TwotypesofBLSR:BLSR/4

BLSR/2


Working connection

A

B

C

working fibers

protection fibers

gADM

ADMADMprotect connection

BLSR/4D

ADM

Figure 10.5


ADM

ADM

ADM

ADM

Working connection

Working/protection fiber

Working/protection fiber

?

BLSR/2ADM

Figure 10.6


BLSR/2issimilarwithBLSR/4 TypesofprotectionschemesBLSR/4

spanswitching(protectionforworkingfiberfailed)

ringswitching(protectionforfiberorcablefailed)

BLSR/2BLSR/2ringswitching

Priorityofprotectionschemesspanswitchingispriortoringswitching


Working connection

A

B

C

working fibers

protection fibers

gADM

ADMADMprotect connection

D

ADM

Figure 10.7 span switching


Working connection

A

B

C

working fibers

protection fibers

gADM

ADMADM Protect connection

D

ADM

Figure 10.8 ring switching


Priority of protection schemesPriorityofprotectionschemes spanswitchingispriortoringswitching spanswitchingcanbecancelledifspanfailsbothonworkingandprotectionpath


Difference between BLSR/4 and BLSR/2DifferencebetweenBLSR/4andBLSR/2BLSR/4deployedinlonghaulcarriers,whileBLSR/2inmetrocarriers

BLSR/4canhandlemorefailuresthanBLSR/2BLSR/4iseasiertoservicethanBLSR/2RingmanagementismorecomplicatedinBLSR/4thanBLSR/2

6.3Protectionin6.3ProtectioninIPNetworksIPNetworks

ProtectioninIPNetworks CharacteristicofIPprotection

Packetsreroutedincorrectlyandpossiblyloop

E

CBA D

Destination:

D

nexthop:Bnexthop:Cnexthop:Dnormaloperationnexthop:Bnexthop:Cnexthop:Bafterfailure,beforeconvergencenexthop:Enexthop:Anexthop:Bafterconvergence

CBA D

Figure 10.13 An example of illustrating routing loops

ProtectioninIPNetworks Slowforalltheroutingtablehavebeenupdated Packets can rerouted on the newly set up LSPs withPacketscanreroutedonthenewlysetupLSPswiththeuseofMPLS

Detectingfailuresslowly AnotheroptionisrelyingontheunderlyingSONETor

opticallayertodetectthefailureandinformtheIPlayer(notusuallyused)

6.4WhyOpticalLayer6.4WhyOpticalLayerProtectionProtection

WhyOpticalLayerProtection

1 way is considered

Save 1 wavelengthLightpath


Benefitofopticallayerprotection:e e o op ca aye p o ec o Canprovideextensiveprotectionfunctionsforclientlayers(IP,SDH).

Significantcostsaving Handlesomefaultsmoreefficientlythantheclientlayer

Can protect multiple failuresCanprotectmultiplefailures Avarietyofmeshbasedprotectionschemesarebeingdeveloped,requiringlessprotectioncapacitythanringbasedschemes


ADM

ADMADM ADMADM

ADM

OXC

OXCOXC OXCOXC

OXC

SONET connectionSONET connection

Lightpath Lightpath

t d li ht th

ADM ADM

OXC OXC

rerouted lightpath

Figure 10.15 Optical layer protection used to enhance SONET protection


Limitations of optical layer protectionLimitationsofopticallayerprotection Notallfailurescanbehandledbytheopticallayer

Opticallayermaynotbeabletodetecttheappropriateconditionsthatwouldcauseittoinvokeprotectionswitching

Theopticallayerprotectstrafficinunitsoflightpaths,cantprotectpartsofthetrafficwithinalightpath


ServiceClassesBasedonOpticalLayerProtectionLevel of Service

Level of connection availablility

Restoration time

Example of protection provider

Platinum highest Fastest(arou-nd 60ms)

Didicated 1+1 protection

Gold high Fast(hundreds of ms)

Shared mesh protection

Silver medium medium Providing gbest-effort

Bronze Low lowest Unprotected lightpaths

Lead Lowest Lowest Used to protect other classes of service

6.5OpticalLayerProtection6.5OpticalLayerProtectionSchemesSchemes

OpticalLayerProtectionSchemes

Opticallayerprotectionislightpathbasedp y p g p OpticalprotectionschemesoperateintheOchorOMS

layers OchlayerpathlayerOMSlayerlinelayer


OpticalprotectionschemesinOMSlayer

OpticalprotectionschemesinOchlayer

Type Dedicated Shared Dedicated SharedTopology Point-point Point-point Ring Ring

1+1 1:1 OMS-DPRing OMS-SPRing

TypeTopology

1+1 Och-SPRingDedicated SharedShared

Ring MeshMesh

Och-Mesh


Protection schemes referred above are ProtectionschemesreferredabovearemostlysimilartotheircounterpartsinSONET/SDH 1+1OMSProtection1+1LineProtection 1:1OMSProtection1:1LineProtectionOMSDPRing(ULSR)UPSRinOMSlayer

OMSSPRingBLSR/4,BLSR/2 1+1OchDedicatedProtection1+1ProtectioninOchlayer

/

Och-Mesh Protection

OchSPRingProtectionBLSR/4inOchlayer OchMeshProtection

Meshprotectionissuitablefordensephysicaltopologies,withtrafficbeingfairlydistributed

Bandwidthefficiencyofmeshprotectioncomparedtoringprotectiondependson3factors

Network topologyNetworktopologyTrafficpatternTypeofmeshprotectionscheme

OchMeshProtectionanexample

Mesh network 1+1 dedicated protectionMesh network 1+1 dedicated protection

Och-SPRing protection Och-Mesh protection

Figure 10.17 Illustration of bandwidth efficiency of mesh protection

Protection is set up dynamically

OchMeshProtection

Protection lightpaths of mesh protection are only set upProtectionlightpathsofmeshprotectionareonlysetupwhenthereisafailure,notaheadoftime.i.e.ituseadynamicrestoration.

OchMeshProtection Themeshprotectionschemeswereabandonedbefore

forslowrestorationtime(orderofminutes),complexlymanagement and no applicable standardsmanagementandnoapplicablestandards.

Reasonfortheresurrectionofmeshprotectionschemes

Theprocessingpoweravailabletoimplementmeshprotectionhasdramaticallyincreased(computingnewroutes)

OXCandotheropticallayerequipmentprotectbandwidthatmuchlargerlightpathsthanDXC

Relativelyfastsignalingandroutingprotocolshavebeendeveloped The60msprotectiontimerequirementisnotahardnumber

Mesh protection is needed deployed requiringMeshprotectionisneededdeployed,requiringfunctionsofroutecomputation,topologymaintenanceandsignalingtosetuptheprotectionroutes

6.6Interworking6.6InterworkingbetweenLayersbetweenLayers

InterworkingbetweenLayers

Theprotectionmechanismsindifferentlayersd l i icanpreventordelayservicerestoration.

Restorationofnetworkconvergeshouldunderrightassumptions

Aviableprotectionpathexistsforeachlayer Theserverlayerisindependentoftheclientlayertodetectfailureand

invokeitsprotectionswitchingfunctions Theclientlayerprotectionisrevertiveandwillrepeatedlytryswitchingtoy p p y y g

theotherpath

Coordinationbetweenprotectionmechanisms Addapriorityamonglayers imposeanadditionalholdofftimeinthehigherlayer

network sdh_optical protection

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