Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

these requirements, but it also needs to present a uniform approach for the
three message store access phases:

1. User and system access for managing the “mailbox”


2. Message deposit


3. Message retrieval

Architecture and Operation

An example is appropriate at this point to illustrate the open architecture for
unified messaging. This architecture is based entirely on the standard proto-
cols SIP, SMTP, HTTP, and RTSP. An example illustrating the operation of the
open architecture for unified messaging is shown in Figure 12.1.

Figure 12.1 Example of open standards based unified messaging operation

1 PSTN or

mobile cell

VoIP

Gateway

SIP Server

3 Call is forked to phone

and to UM server

4 Called party

does not answer

Message

retrieval by

voice

Web retrieval and

playback using RTSP

5 Message

store takes

call after

timeout

7 NOTIFY

6 e-mail notification

UM Server

Unified Message Store

2

3

3

Voicemail and Universal Messaging 211