Subject: [Sip] Question on ReliableProvisional Resp and Early Media

From: [email-masked]
Date: Thu, 4 Aug 2005 12:43:00 +0530

Hi all,

I have some questions:-

1) Why as per RFC 3262, the Offer-Answer is a MUST in the Provisional
Resp+PRACK phase?

2) If the 3262 is only for Reliability of Provisional responses, Why should
it mandate Offer-Answer completion?

3) As per current recommendations (that are evolved as per discussions in
the sip groups), Why we can not send new Offer in the 200 OK to the INVITE,
after establishing the early media?

4) If we can not change the media using 200 OK to INVITE, how this early
Media is useful?

5) Are we seriously missing some thing in 3262, that forced us to come up
with 3311 (UPDATE)?

Thanks in advance,

rgds,
Prince

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---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 04 Aug 2005 05:33:11 -0400

> 1) Why as per RFC 3262, the Offer-Answer is a MUST in the Provisional

I have yet to find anyone who could explain the WHY to me. However that 
is the way it is. People have asked in the past if this could be 
changed. The answer is that it perhaps could be changed, but the effort 
and impact of doing it would be considerable, and you would still be 
stuck supporting the old cases for backward compatibility. There are 
ways to adhere to the current requirement, so its hard to justify making 
a change.

> it mandate Offer-Answer completion?

Again, I am not sure it is possible to answer why. What some people have 
proposed for a rationale is that there should be at most one 
offer/answer per transaction.

> after establishing the early media?

There was extensive discussion of this about a year and a half ago. 
There were differences in interpretation of this, and finally it was 
decided that there can be at most one offer/answer per transaction.

At this point, that is just the way it is.

> 4) If we can not change the media using 200 OK to INVITE, how this early

You may establish early media with a 1xx to the invite, and then change 
to some other media via an UPDATE sent prior to the 2xx.

> 5) Are we seriously missing some thing in 3262, that forced us to come up

Perhaps. The UPDATE permits changes in media, initiated in *either* 
direction, prior to completion of the invite.

	Paul

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>

---

From: "BAKIR YILDIRIM" <[email-masked]>
Date: Thu, 4 Aug 2005 12:33:29 +0200

Can u take out my email from your discussions
thanks

BAKIR Yildirim 
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-----Message d'origine-----
De : Paul Kyzivat [mailto:[email-masked]] 
Envoyé : jeudi 4 août 2005 11:33
À : [email-masked]
Cc : [email-masked]; [email-masked]
Objet : Re: [Sip-implementors] Question on ReliableProvisional Resp and
EarlyMedia

a change.

	Paul