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Chapter 7.  Voice-Mail System Design

Chapter 7.  Voice-Mail System Design

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collectthecustomerrequirementsanddesignthevoice-mail

systemaccordingly.



DefiningtheVoice-MailSystemArchitecture

Figure7-1showstheproposedvoice-mailarchitectureforXYZ.

TheCiscoUnitysystemthatisdeployedinUnifiedMessaging

modereplacestheOctelvoice-mailsysteminSydney.Inthe

SanJoselocation,theOctelvoice-mailsystemwillremain.The

SeattleandDallassitesusetheexistingOctelvoice-mailsystem

inSanJose.



Figure7-1.Voice-MailDeploymentModelofXYZ



[Viewfullsizeimage]



IntegrationbetweentheCallManagerclusterinSanJoseand

theOctelvoice-mailsysteminSanJoseisdonebyusinga

CiscoDigitalPortAdapter(DPA-7630).TheCiscoDPA-7630

communicateswiththeOctelvoicemailsystemusing24digital

phonelines.DPA-7630usestheSkinnyClientControlProtocol

(SCCP)tocommunicatewithCallManager.BecauseXYZuses

thevoice-mailsystemasanetworkingservice(meaningall

employeescannetworkmessagestoeachotherviadirect

addressingorbyusingvoice-maildistributionlists)integration

andinteroperabilitybetweentheOctelnetworkandtheCisco

Unityenvironmentneedstobemaintained.Therefore,useof

theCiscoUnityBridgeisnecessaryinthissetup.The

communicationbetweentheCiscoUnityserverinSydneyand

theUnityBridgeinSanJoseusesaSimpleMailTransfer

Protocol(SMTP)connection,andthecommunicationbetween

theUnityBridgeandtheOctelsysteminSanJoseisviaan

analogconnection.

ThecallflowformessagesaddressedfromaUnity-userin

SydneytoanOctel-userSanJoseisasfollows:Thevoicemail

messageaddressedintheUnitysysteminSydneytoanOctel

subscriberinSanJose,travelsviatheinternalIPnetworkover

anSMTPconnectionandreachestheUnityBridgeinSanJose.

TheUnityBridgewillthenpackagethisvoicemailmessageas

anAnalogOctelNetmessageandplaceacall,viatheVG248,to

theOctelsysteminSanJose.ThiscallwillgothroughtheDPA

(whichistheinterfacebetweentheCallManagerandtheOctel

system)toreachtheOctelSystemandcompletetheanalog

networkingcall.

Thecallflowfortheoppositeissimilar.Whenavoicemail

messageisaddressedfromanOcteluserinSanJosetoa

Unity-userinSydney,theOctelSystemplacesacalltothe

UnityBridge.ThecallgoesfromtheOctelsystemportsthatare

connectedtotheDPAandreachestheVG248whichhousesthe



analogextensionsfortheUnityBridge.TheUnityBridgethen

repackagestheOctelNetmessagestoanSMTPmessageand

sendsitovertheinternalnetworktotheUnityserverinSydney.

UnitysubscribersintheSydney,Melbourne,andBrisbanesites

canaccessvoice-mailmessagesviatheirIPPhones,cell

phones,oranyotherexternalphone.Inaddition,Unitywill

activatethemessagewaitingindicator(MWI)onthephoneof

therelatedsubscriberandprocesstheOutcallnotificationstoa

pager,cellphone,orhomephone,whicheverisconfiguredby

thesubscriber.Subscriberscanalsoaccessvoice-mailmessages

viaawebbrowserandcancustomizetheirmailboxsettings,

suchasgreetings,Outcallnotifications,andsoon.

IntheUnifiedMessagingenvironment,thevoice-mailmessage

isdeliveredtothesubscriberintheircommon(e-mailand

voice-mail)inbox.



MicrosoftActiveDirectoryandExchange

UnityintegrateswithADandheavilyreliesonthemessaging

infrastructure.UnitysupportsMicrosoftExchange2000or2003

andIBMLotusNotesasthemessagestore.Therefore,

understandingthemessagingarchitectureisimportantwhen

youaredesigningtheUnitysystem.

AprerequisitefordeployingUnityinaUnifiedMessagingmode

isthattheADdomainandExchange2000/2003orIBMLotus

Notesenvironmentissetupandworkingproperly.Exchange

5.5supportisnotanoptionwithUnityversions4.0andabove.

Unitycananswercallsandtakevoice-mailmessagesjustlike

theOctelvoice-mailsystemsthatarepartiallyreplacedinthis

casestudy.Thesubscribercanretrievetheirmessagesthrough

anyofthefollowingchoices:



Byusingthephone

ByusingMicrosoftOutlook

ByaccessingtheCiscoUnityInboxviathewebinterface



Note

BecauseXYZusesMicrosoftExchangeasamessage

store,useofIBMLotusNotesisnotapplicablefor

thiscasestudy.



UnityrequiresextensionstotheADschema.UnityusesADto

servicesubscriberswhosemailboxesresideonExchange2000.

Unitydoesthisbyextendingtheschemawiththeadditionof

theUnityattributesforthefollowingobjects:

User

Group

Contact

UnityLocation(newlycreatedobject)

UnityLocationisaspecialobjectthatallowsUnityserversto

identifythemselvestootherUnityserversintheenterprise.Itis

usedonlybyUnityservers.

Toviewthelistofattributesaddedforeachobject,theirvalues,

andtheimpactonthesizeoftheADdatabase,usethe



followingURL:



http://www.cisco.com/en/US/partner/products/sw/voicesw/ps2237/prod

ToseethechangesmadetotheADschema,browsetothe

directorySchema\LdifScriptsonCiscoUnityCD1,andviewthe

fileAvdirmonex2k.ldf.IftheextensionoftheADschemaisnot

acceptable,deployanewADandExchangeenvironmentand

deployUnityasavoice-mail-onlysolution.AftertheITteamor

theenterprisemessaging/directoryteamiscomfortablein

extendingtheschema,itispossibletomigratetoUnified

Messagingandusethecorporatemessaginginfrastructure.



ActiveDirectoryArchitecture

AkeyrequirementbeforeyoudesignaUnitysystemanddeploy

itintoanetworkistounderstandtheexistingADand

messagingarchitecture(MicrosoftExchange/LotusDomino).

Figure7-2showstheADarchitectureforXYZ.Youcanseethat

XYZhasasingleADforestfortheentireorganization.Fromthe

ADpointofview,therearetwositesSanJoseandSydneyeach

ofwhichhasadomaincontroller(DC)andaGlobalCatalog

(GC)server,asshownpreviouslyinFigure7-1.



Figure7-2.ActiveDirectoryArchitectureofXYZ



Exchange2000MessagingArchitecture

AsFigure7-3shows,theExchange2000messaging

architecturefortheXYZSanJoseandSydneysiteshas

Exchange2000servers.TheSanJosesitehasthreeExchange

servers,andtheSydneysitehastwoExchangeservers.



Figure7-3.Exchange2000Messaging

ArchitectureofXYZ



[Viewfullsizeimage]



XYZdefinedroutinggroupsonaper-sitebasis,oneforSanJose

andoneforSydney.GroupsofserversrunningExchange2000

formroutinggroups.Typically,permanenthigh-speedlinks

connecttheserverswithinthesameroutinggroup.Arouting

groupconnectorconnectstwodifferentroutinggroups.

MicrosoftExchangeusesroutinggroupconnectorsand

Bridgeheadserverstoroutethemessagesbetweendifferent

routinggroups.BridgeheadserversrunExchange2000and

hostroutinggroupconnectors.

IntheXYZenvironment,amessagefromauserinSanJoseto

auserinSydneytravelsviatheroutinggroupconnector.

Messagesbetweentheserverswithinthesameroutinggroup

aresentdirectlyfromthesourceservertothedestination

serverusingSMTP.



UnityDeploymentModel

AfteryouunderstandtheADandmessagingarchitecture

deployedatXYZ,thenextstepistochoosetheUnity



deploymentmodel.Threetypesofdeploymentmodelsare

availablewhendeployingUnity:

CentralizedUnityserversarecollocatedwiththemessage

storeserversandthephonesystem.

DistributedUnityserversarenotcollocatedwiththe

messagestoreserversandthephonesystem.

HybridThisisamixofthecentralizedanddistributed

models.Unityserverscanbedeployedatacentrallocation

andatremotesitesthathavenumeroususers.

Whenchoosingthedeploymentmodelconsiderthefollowing

factors:

UnityintegrationwiththephonesystemIfthe

integrationisanalog,suchasSMDI,cablelength

requirementsmightforceyoutohaveCiscoUnityservers

collocatedwiththephonesystem.

LocationofthemessagestoreIfthemessagestoreis

centralized,placetheUnityserverswiththemessagestore

serversatthesamelocation.TodeployUnityserversina

differentlocationfromthemessagestoreservers,ensure

thatthereisaLANconnectionthatconnectsthelocations

andthatishighlyreliable,haslessround-tripdelaytime,

andhashighbandwidthtoavoidsynchronizationissues.

ForXYZ,becausethemessagestoreserversandCallManager

systemareinSydney,deployingUnityserversinSydneyis

ideal.AcentralizedUnitydeploymentmodelsuitsthislocation

becausetheremotesitesinMelbourneandBrisbanehavefewer

usersanddonothavesignificantbandwidthimplications.The

usersatSydney,Melbourne,andBrisbaneaccesstheUnity



systeminSydneyfortheirvoicemails.



PhysicalPlacementofUnityServers

ThebestpracticeistodeploytheUnityandExchangeservers

onthesamesubnetinaLANenvironment,forthefollowing

reasons:

UnityusesMailApplicationProgrammingInterface(MAPI)

tocommunicatewithExchange.

MAPIusesremote-procedurecall(RPC)asatransport

protocol.

RPCisachattyprotocol,soitcanintroducedelaysover

slow-speedlinksandcauseproblemswhilepassingthrough

firewalls.

XYZhasanalreadyoperationalExchange2000environmentin

itsregionalhubofSydney.Therefore,theSydneydatacenteris

theidealplacetodeploytheUnityserver.



HighAvailability

Manyorganizationsrelyonnetworkedvoicemailasanessential

businesstooltoenableacallertoleaveamessageifthe

employeewhomtheyarecallingisunavailabletopickupthe

phoneortosendmessagesdirectlytoanotheremployee's

mailbox.Therefore,thehighavailabilityofthevoice-mail

systemiscritical.

ClusteringisnotcurrentlyavailableontheUnityservers.To

achievehighavailability,deployUnityserversinactive/standby



pair,wherebyoneserverissittingidleuntiltheactiveonefails.

ForXYZtoachievehighavailability,itwilldeploytwoUnity

serversinSydney.



SecuringUnityServers

AsdiscussedinChapter6,"DesignofCall-Processing

InfrastructureandApplications,"XYZhasgoodpracticesin

placeforsecuringtheCallManagerservers.ToprotecttheUnity

serverssimilarly,XYZplanstodothefollowing:

Installthevirus-scanningsoftwareandtheCiscoSecure

Agent(CSA)forintrusiondetectionontheUnityandUnity

Bridgeservers.

ApplyallCisco-recommendedsettings,securitypatchesand

operatingsystemservicepackstotheserversfromthe

momenttheybecomeavailable.

Implementthephysicalsecurityforthecomputerroomin

SydneywhereUnityserversareplaced.



BackupofUnityServers

TheproceduretobackuptheADforestandtheExchange2000

environmentisalreadyinplaceintheXYZnetwork.Addthe

Unityserverstothelistofserversandperformtheregular

backups.UnlikeCallManagersoftware,whichbundlesthe

backuputility,Unitydoesnotincludeabackuputility.Cisco

recommendsusingVERITASNetBackupsoftware

(http://www.veritas.com/).



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