Nortel Networks NN10029-111 Back-to-Back User Agent service UserA, Agent Client Internal Protocol

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Nortel Networks Confidential	Overview 5

—changing IP addresses in the contact header so that the SIP Application Module remains on the signaling path

—modifying the Session Description Protocol (SDP) using values supplied by the RTP Media Portal to control media endpoints

—providing advanced screening capabilities

The architecture of a BBUA service consists of two user agent clients linked back-to-back through a proprietary interface.

The BBUA is guaranteed to be on the signaling path of all future requests and responses because it is an endpoint relative to the SIP network components. This is important for services such as billing, which need to be aware of all events that take place on a session. The BBUA in the network also provides a barrier for clients that are not fully SIP compliant and entry and exit points for traffic travelling to and from the public network, including agents behind an enterprise firewall. See Figure 1, “Back-to-Back User Agent service.”

Figure 1 Back-to-Back User Agent service

userA	User	User	userB
userA	Agent	Agent	userB
	Client	Client
	Internal Protocol

Routing in a SIP network is based on the same hop-by-hop principle as routing e-mail within the Internet. The next hop for a SIP request is determined by a proxy using the domain or the host part of a SIP URL (user@domain). The terminating proxy determines whether the domain sent in the SIP URL is one of the domains managed by the SIP proxy. Otherwise, the SIP request is forwarded to another Proxy based on the location lookup performed by the

SIP Application Module. The SIP Application Module supports routing using table lookup in the SIP database or using the Domain Name Server (DNS) to find a route.

Copyright © 2003, Nortel Networks

MCP SIP Application Module Basics

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Contents MCP SIP Application Module Page How this chapter is organized OverviewFunctional description OverviewAgent Client Internal Protocol Back-to-Back User Agent service UserANetwork configuration BiggerMart.com BigMart.comPublic network InterfacesProtocols PCPSQL Hardware Services and featuresRouting and Translation services Foreign termination Telephony routing Call Transfer serviceLocal termination Relationship between Telephony routing stages SIP Aliases Multiple Route Termination Call Processing Language Interworking services Discriminator serviceService package enforcement Privacy Control serviceAuthentication services Bearer Path ControlConverged PC service Network/Address Hiding service Enterprise Clients Notification support Voicemail server interoperability and MWI Instant MessagingPresence Nortel Networks Confidential Overview Registration-static and dynamic Overload control Network address bookReliability and fault tolerance Manual failover OAM&P strategy Updating the SIP Application Module software UpgradesUpdating the Application Module from the menu tree Updating the SIP Application Module from the pull-down menu Load list for updating Progress of update Page Procedure 1 Clearing the SLE701 Slee Health Monitor alarm Alarm clearing proceduresProcedure 2 Clearing the SMDI101 alarm Configuration Configuration Nortel Networks Confidential Displaying help text Adding a component Procedure 1 Adding a componentAdding a component Configuration window top half Adding Services Progress dialog box Configuring the SIP Application Module tabs Field Value Description Application Server tab field descriptions Sheet 2Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential URL Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential Completing the Database Base tab fields DNS SRV Completing the Data Synchronization tab fields Locate User Svc tab field descriptions Sheet 2Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Completing the Local Accounting Manager tab fields Completing the In Memory Database tab fields Configuration Nortel Networks Confidential Memory Database tab field descriptions Sheet 2 Completing the Location Service tab fields Location Service tab field descriptions Sheet 2 Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Privatestaticaddress whose value Server.blade.host.label forCompleting the Server Subscription tab fields Addrsip Porthttp Portprotocol Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential SipFwdAdapter tab field descriptions Sheet 2 Completing the Transport Management tab fields Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Configuration Nortel Networks Confidential Nortel Networks Confidential Configuration Figure above Nortel Networks Confidential Configuration Transport Management tab subfields, cont’d Transport Management tab subfield descriptions Active-standby server group configuration Nortel Networks Confidential Configuration TCF Config details Additional SIP TCF Base tab configuration informationUDP/TCP/SSL Config values Parameter Value Description ExampleRetransmission Off parameter Invite Timer parameterCheck Mandatory Headers parameter Add Defaults parameterTime Transaction parameter Accounting management Page Performance management Page Security Security and AdministrationPage Voice plus video Appendix a Basic call flowsClient-to-client voice plus video diagram Application Client a Module Client B Client-to-client voice plus video call flowCall transfer Call transfer to client diagram Client a Client C Client BApplication Client a Module Client B Client C Call transfer blind to client call flowAppendix a Basic call flows Nortel Networks Confidential Failed call transfer call flow Appendix a Basic call flows Nortel Networks Confidential Authentication diagram AuthenticationApplication Client a Module Database Authentication call flowNortel Networks Confidential Appendix a Basic call flows Page Page Page Page MCP SIP Application Module