Subject: [Sip] RFC3262 -The Offer/Answer Model and PRACK (question)

From: "Kasturi Narayanan" <[email-masked]>
Date: Thu, 7 Apr 2005 17:04:52 -0500

I have a question related to the following sentence in the RFC3262.

Here is the sentence in Section 5 of the RFC 3262

"Similarly, if a reliable provisional response is the first reliable message
sent back to the UAC, and the

INVITE did not contain an offer, one MUST appear in that reliable
provisional response."

Why is it made mandatory that, when INVITE(without offer) should always
result in a 18x(with Offer) if 18x is reliably sent?

However in the RFC it is not mandatory to include Answer in 18x if Invite is
sent with an OFFER.

If there are cases where a Sip UAS wants to send 180 Ringing reliably
(without Offer) so that the remote UAC can generate local Ring back and at
the same time wants to send Offer in 200 OK only   and get the answer in ACK
only.

Why the above condition is not a valid condition?  Please clarify

Thanks

Kasturi Narayanan,

_______________________________________________
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

---

From: Paul Kyzivat <[email-masked]>
Date: Thu, 07 Apr 2005 20:31:02 -0400

There was a long discussion of this several months ago.

I don't know why this requirement is there, and I don't recall that the 
discussion explained why. As I recall the discussion, the outcome was 
more or less: That is the way it was specified and it is too late and 
hard to change. There are ways for everybody to comply, so just do it.

I'm sure somebody will correct me if my memory is bad. (I could probably 
find the thread if I tried hard enough, but I've got other things to do 
now.)

	Paul

Kasturi Narayanan wrote:
> “Similarly, if a reliable provisional response is the first reliable 
> message sent back to the UAC, and the
> 
> provisional response.”
> However in the RFC it is not mandatory to include Answer in 18x if 
> Invite is sent with an OFFER.
> 
>  
> 
> (without Offer) so that the remote UAC can generate local Ring back and 
> at the same time wants to send Offer in 200 OK only   and get the answer 
> in ACK only.
> 
>  
> 
> */Kasturi Narayanan,/*
> */ /*
> ------------------------------------------------------------------------
>

---

From: "Kasturi Narayanan" <[email-masked]>
Date: Thu, 7 Apr 2005 22:14:37 -0500

Thanks Paul for the reply, Even though it is not very convincing that why it
should be left as it is, if no reason can be attributed to it and also does
not seem right to put across an argument that somehow that requirement can
be complied so why undo the mistake.

-regards
Kasturi

-----Original Message-----
From: Paul Kyzivat [mailto:[email-masked]] 
Sent: Thursday, April 07, 2005 7:31 PM
To: Kasturi Narayanan
Cc: [email-masked]
Subject: Re: [Sip] RFC3262 -The Offer/Answer Model and PRACK (question)

	Paul

Kasturi Narayanan wrote:
> "Similarly, if a reliable provisional response is the first reliable