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

Figure 7.2 Call-forward, no-answer service implemented by the called user agent

Calling User Agent Implementation

Finally, Figure 7.3 shows how this same feature can be implemented in the call-

ing SIP phone. In this case, the SIP server redirects, instead of proxying the

INVITE:

302 Multiple Choices

Contact: <sips:[email protected]>

Contact: <sips:[email protected]>

;actor=msg-taker;automata

Proxy Server

1 INVITE

3 100 Trying

6 180 Ringing

2 INVITE

4 100 Trying

5 180 Ringing

Phone sends

redirection to

voicemail server

response after

timer expires.

7 302 Moved Temporarily

8 ACK

12 INVITE

14 200 OK

17 ACK

Media Session Established

11 INVITE

13 100 Trying

9 302 Moved Temporarily

10 ACK

15 200 OK

16 ACK

SIP Caller SIP Phone Voicemail Server

138 Chapter 7