Re: [Sip] SIPit21: SDP in a 200OK when using 100rel

On Nov 21, 2007, at 5:15 PM, Paul Kyzivat wrote:
>
> That may seem simple and harmless. But it gets ugly when additional  
> offer/answers happen:
>
>   Alice               Bob
>     |  INVITE offer1   |
>     |----------------->|
>     |  183 answer1     |
>     |<-----------------|
>     |  PRACK           |
>     |----------------->|
>     |  200 PRACK       |
>     |<-----------------|
>     |  UPDATE offer2   |
>     |<-----------------|
>     |  200 UP answer2  |
>     |<-----------------|
>     |  200 IN SDP?     |
>     |<-----------------|
>
> Now what should be in the 200 for the invite?
>
> Its better to do what is already required - send no SDP in the 200  
> for the invite.

Huh. Is it actually ok to send a 200 OK for the UPDATE before sending  
the 200 OK for the INVITE? That seems like a race condition from hell.

If it's OK only because you can claim the INVITE's O/A sequence  
completed before the UPDATE was sent, then we're making the SIP state  
machine dependent on the O/A model, and that's just wrong.

--
Dean

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use sip-implementors@cs.columbia.edu for questions on current sip
Use sipping@ietf.org for new developments on the application of sip