User's Manual

22 Overview

Nortel Networks Confidential

For more information and the procedure for setting up Instant Message

notifications to emergency numbers, see the SIP Provisioning Client

User Guide.

Instant Messaging

Instant Messages are routed in parallel only to a subscriber's

dynamically registered routes (see “Registration—static and dynamic”

on page 24). This is in contrast to session initiation requests, which are

subject to CPL routing logic. Upon receipt of an instant message, a

client may respond back to the address supplied in the Contact header.

This ensures that the response is sent back to the same client device

that originally sent the message.

Presence

When a user initially registers, by default their presence status is set to

“on-line” in the SIP registration message. Users subscribe to watch the

status of other users, and to coordinate the status of their own devices.

This information is maintained in an in-memory table on the SIP

Application Module (Presence software). The information that is stored

in this table includes:

• the user to be watched

• the party requesting the subscription

• the correlation information identifying that particular subscription

request

• contact information regarding where to send the notifications that

are generated as a result of the subscription being active

When a user changes their presence (for example, to Busy), a

registration message is automatically sent to the SIP Application

Module.

The SIP Application Module then checks its in-memory table to see

what their previous presence state was. If the update causes a material

change in their presence state, the SIP Application Module looks up

which users need to be notified of the change (also in memory). This

is done by sending a Notify message to each user at every contact

contained in the table. For more information, refer to the MCP SIP

Presence Basics document.

Voicemail server interoperability and MWI

In order to accomplish voicemail server interoperability and MWI

(message waiting indication) notification, the SIP Application Module