SMS

| F1 MESSAGE | |
|--------------------> | F2 MESSAGE |
| | ----------------------->|
| | |
| | F3 200 OK |
| | <-----------------------|
| F4 200 OK | |
|<-------------------- | |
| | |
| | |
| | |
User 1 Proxy User 2



Message F1 looks like:
MESSAGE sip:user2@domain.com SIP/2.0
Via: SIP/2.0/TCP user1pc.domain.com;branch=z9hG4bK776sgdkse
Max-Forwards: 70
From: sip:user1@domain.com;tag=49583
To: sip:user2@domain.com
Call-ID: asd88asd77a@1.2.3.4
CSeq: 1 MESSAGE
Content-Type: text/plain
Content-Length: 18

Watson, come here.


F2, looks like:
MESSAGE sip:user2@domain.com SIP/2.0
Via: SIP/2.0/TCP proxy.domain.com;branch=z9hG4bK123dsghds
Via: SIP/2.0/TCP user1pc.domain.com;branch=z9hG4bK776sgdkse;
received=1.2.3.4
Max-Forwards: 69
From: sip:user1@domain.com;tag=49394
To: sip:user2@domain.com
Call-ID: asd88asd77a@1.2.3.4
CSeq: 1 MESSAGE
Content-Type: text/plain
Content-Length: 18

Watson, come here.


SIP/2.0 200 OK
Via: SIP/2.0/TCP proxy.domain.com;branch=z9hG4bK123dsghds;
received=192.0.2.1
Via: SIP/2.0/TCP user1pc.domain.com;;branch=z9hG4bK776sgdkse;
received=1.2.3.4
From: sip:user1@domain.com;tag=49394
To: sip:user2@domain.com;tag=ab8asdasd9
Call-ID: asd88asd77a@1.2.3.4
CSeq: 1 MESSAGE
Content-Length: 0




SIP/2.0 200 OK
Via: SIP/2.0/TCP user1pc.domain.com;branch=z9hG4bK776sgdkse;
received=1.2.3.4
From: sip:user1@domain.com;;tag=49394
To: sip:user2@domain.com;tag=ab8asdasd9
Call-ID: asd88asd77a@1.2.3.4
CSeq: 1 MESSAGE
Content-Length: 0