Subject: RE: [Sip] PRACK query

From: "Christer Holmberg" <[email-masked]>
Date: Fri, 29 Sep 2006 17:32:40 +0300

Hi,

If you want to use a different SDP in 200 OK you need to use a different To tag. You can not "update" an answer within the same dialog by sending a new SDP in 200 OK.

Regards,

Christer

________________ Reply Header ________________
Subject:	RE: [Sip] PRACK query
Author:	[email-masked]
Date:		29th September 2006 7:07:48 pm

SDP in 1xx response and 200 OK can be different because of early media 
announcements and actual calle connected.

If 200 OK SDP will be same, then how can early media will be 
differentiated with regular session
(basically early media is used for announcements and 200 OK will tell the 
actual callee connected)

Regards,
Udit

"Christer Holmberg \(JO/LMF\)" <[email-masked]> 
09/28/2006 07:46 PM

To
Udit Goyal/C/US/3Com@3Com, <[email-masked]>
cc
[email-masked]
Subject
RE: [Sip] PRACK query

Hi,

>Please let me know if my understanding is correct for regular session
offer-answer when PRACK is used:
>
>For INVITE containing SDP, and if offer answer done in the using
reliable 183 response for early media, 200 OK response SDP will have an
answer for the
>regular session, so 200 OK SDP will be answer to the offer sent in
initial SDP.

Yes.

Of course, since you have already received the answer reliably, you
really don't need to care about the SDP in 200 OK, but according to the
rules it should be the same as previously sent in 18x.

>Similarly, if INVITE does not  have SDP, and if offer-answer done using
PRACK, still 200 OK will contain the regular session offer and answer
will be
>present n the ACK message.

I would assume so, yes. But, again, you don't really need to care.

>Similarly, if UPDATE is used for offer-answer before call is connected,
it will not affect the regular session offer-answer, it will be taken
care by
>initial INVITE , final 200 OK and ACK message.

I don't know what you mean by "not affect".

If you send an offer in INVITE, and receives an answer in a reliable
18x, the offer/answer exchange in UPDATE will then replace the one
previously done.

But, yes, the SDP you get in the 200 OK should still be the same that
you got in 18x, even if you have performed offer/answer exchanges after
that.

At least this is how I understand it - but you can never be sure when it
comes to offer/answer :)

Regards,

Christer

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_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip