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

Figure 13.9 Example message flow for SIP based instant messaging

SIPMESSAGEis similar to the SIPINVITE. Here are two message examples

for Figure 13.9.

Message 1

MESSAGE sip:[email protected] SIP/2.0

Via: SIP/2.0/TCPuser1pc.domain.com;branch=z9hG4bK77

Max-Forwards: 70

From: <sip:[email protected]>;tag=49583

To: sip:[email protected]

Call-ID: [email protected]

CSeq: 1 MESSAGE

Content-Type: text/plain

Content-Length: 18

Watson, come here.

Message 2

MESSAGE sip:[email protected] SIP/2.0

Via: SIP/2.0/TCP proxy.domain.com;branch=z9hG4bK123

Via: SIP/2.0/TCP ser1pc.domain.com;branch=z9hG4bK77

;received=1.2.3.4

Max-Forwards: 69

From: <sip:[email protected]>;tag=49394

To: sip:[email protected]

Call-ID: [email protected]

CSeq: 1 MESSAGE

Content-Type: text/plain

Content-Length: 18

Watson, come here.

User 1

1. MESSAGE
   2. MESSAGE
   3. 200 OK


2. 200 OK

Proxy User 2

240 Chapter 13