User's Manual

16 Overview

Nortel Networks Confidential

With simultaneous ringing, the call terminates to multiple routes at the

same time. The first terminating route to answer is accepted and the

rest of the routes are released.

With sequential ringing, the call tries to terminate to only one of several

routes at a time. Route advancement occurs whenever an error

response is received, a provisionable No Answer timer expires, or a

redirect response is received.

Call Processing Language

The SIP Application Module supports the use of the Call Processing

Language (CPL), based on the IETF CPL draft, draft-ietf-iptel-cpl.txt.

SIP clients can change the behavior of a session using a CPL script

that contains general directives for routing a request.

For example, subscribers can include CPL scripts in the body of

registration requests that contain instructions for location lookups and

call screening, a process that is actually done through the Call Manager

in the Personal Agent. Third-party clients can also upload scripts using

the Registration mechanism. The Registration function of the

SIP Application Module stores the request. When the SIP Application

Module is queried for routing information for a subscriber who has valid

data stored in the database, the software returns the script along with

the routing information. The SIP Application Module applies the CPL

script to the returned routes and can eliminate or alter the routes based

on the CPL script.

CPL scripts do not support the following:

• Remove location

• Mail option

• Log option

Interworking services

Discriminator service

The SIP Application Module screens requests bound for devices that

are not fully SIP compliant, for example, the Communication Server for

Enterprise (CSE) 2000. These components cannot process all types of

signaling and certain media change requests. Therefore, the

SIP Application Module either performs the requested operation or

rejects the request and responds with an error response.

The Discriminator service works with various gateways and SIP clients

using provisioning facilities implemented by the SIP Application

Module. As gateways or SIP clients with limited SIP capability are

added to the network, this service can be configured to support these