This document defines a Session Initiation Protocol (SIP) event

package for registrations-This document defines a Session Initiation Protocol (SIP) event

package for registrations. Through its REGISTER method, SIP allows a

user agent to create, modify, and delete registrations.

Registrations can also be altered by administrators in order to

enforce policy. As a result, these registrations represent a piece

of state in the network that can change dynamically. There are many

cases where a user agent would like to be notified of changes in this

state. This event package defines a mechanism by which those user

agents can request and obtain such notifications.