Subject: [Sip] PRACK query

From: [email-masked]
Date: Thu, 28 Sep 2006 19:29:11 +0530

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.

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.

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.

Thank,s
Udit

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From: "Christer Holmberg \(JO/LMF\)" <[email-masked]>
Date: Thu, 28 Sep 2006 16:16:11 +0200

Hi, 

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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From: Paul Kyzivat <[email-masked]>
Date: Thu, 28 Sep 2006 11:54:02 -0400

This is a complex subject. Start by reading

http://www.ietf.org/internet-drafts/draft-sawada-sipping-sip-offeranswer-01.txt

If that doesn't answer your questions, then ask again.

	Paul

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> [email-masked]
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>

---

From: [email-masked]
Date: Fri, 29 Sep 2006 19:07:48 +0530

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,

initial SDP.

Yes.

Regards,

Christer