Nortel Networks NN10029-111 manual Overview, Functional description

4 Overview Nortel Networks Confidential

Overview

The SIP Application Module is a service execution engine that provides the following functionality:

•core signaling functionality enabling communication among SIP clients

•SIP proxy server

•Back-to-Back User Agent

•SIP Registration

•CPL interpretation

•Location server

•optional Presence subscription and notification (For more information on the Presence feature, see the MCP SIP Presence Basics document.)

The SIP Application Module handles SIP sessions and applications and provides the core services that enable communication between SIP clients. The SIP Application Module is housed on the SIP Application Server.

Functional description

The SIP Application Module includes the following components:

•Back-to-Back User Agent (BBUA)/Proxy Server

Although the BBUA and Proxy Server are basically two different logical entities within the same physical server, they both act as clients and servers. The SIP Application Module decides on a call-by-call basis whether to process the request as a pure Proxy or BBUA.

The Proxy Server processes SIP requests and responses, rewrites headers, modifies request-URIs (Universal Resource Indicator), performs location look-up, and forwards requests to SIP clients or other servers in the network.

The SIP Application Module provides a fully session-stated proxy; in other words, the SIP Application Module maintains a call state for the entire session.

The BBUA extends the proxy function to perform advanced functions such as

—originating new calls

—tearing down existing calls

—modifying messages

NN10029-111 Standard MCP 1.1 FP1 (02.02) April 2003 Copyright © 2003, Nortel Networks