Subject: Re: [Sip] Query on 'new offer' during INVITE-PRACK transaction

From: [email-masked]
Date: Tue, 17 Dec 2002 17:40:03 +0530

Hi,
     " If the initial offer is in an INVITE, the answer MUST be in a
     reliable non-failure message from UAS back to UAC which is
     correlated to that INVITE. For this specification, that is
     only the final 2xx response to that INVITE. That same exact
     answer MAY also be placed in any provisional responses sent
     prior to the answer. * The UAC MUST treat the first session
     description it receives as the answer, and MUST ignore any
     session descriptions in subsequent responses to the initial
     INVITE.* ",

       According to the above excerpt from RFC 3261, you cant send a
*newoffer* in 200 OK.
If an *answer* is sent in any Reliable Provisional Response,then any
session description in subsequent
responses(including 200OK for INVITE) should be ignored.So,though you send
a *newoffer*, your session
description in 200OK will be ignored.

If at all you want to propose a *newoffer*,you should use *Update* for the
same.

regds,
srikanth sundaragopalan

OKUMURA Shinji <[email-masked]> on 12/17/2002 05:15:00 PM

To:   [email-masked]
cc:    (bcc: Srikanth Sundaragopalan/HSSBLR)

Subject:  [Sip] Query on 'new offer' during INVITE-PRACK transaction

Hi Folks,

I have one question concerning a new offer inclusion during a transaction
of
INVITE-PRACK at stated in the following figure.

Here my question goes, is it possible to include a new 'offer 2' within 200
INVITE at line (5) and the corresponding 'answer 2' in ACK at line (6)?

Thanks in advance for your kind response.

Caller                        Callee
   |                             |
   |                             |
   |(1) INVITE with offer 1      |
   |---------------------------->|
   |                             |
   |                             |
   |(2) 180 INVITE with answer 1 |
   |<----------------------------|
   |    Require: 100rel          |
   |                             |
   |                             |
   |(3) PRACK                    |
   |---------------------------->|
   |                             |
   |                             |
   |(4) 200 PRACK                |
   |<----------------------------|
   |                             |
   |                             |
   |(5) 200 INVITE with offer 2  |
   |<----------------------------|
   |                             |
   |                             |
   |(6) ACK with answer 3        |
   |---------------------------->|
   |                             |
   |                             |

Best regards,
_________________________________________________________
OKUMURA Shinji               E-mail:[email-masked]
_______________________________________________
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This list is for NEW development of the core SIP Protocol
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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

---

From: OKUMURA Shinji <[email-masked]>
Date: Wed, 18 Dec 2002 20:10:17 +0900

Hi Srikanth,

Thank you very much for your response. I have gotten the answer but I wish 
to understand the reason behind for adopting such regulation. For example, 
consider the following two transaction scenarios side by side.

Caller                        Callee    Caller                        Callee
   |                             |         |                             |
   |                             |         |                             |
   |(1) INVITE with offer 1      |         |(1) INVITE with offer 1      |
   |---------------------------->|         |---------------------------->|
   |                             |         |                             |
   |                             |         |                             |
   |(2) 180 INVITE with answer 1 |         |(2) 180 INVITE with answer 1 |
   |<----------------------------|         |<----------------------------|
   |    Require: 100rel          |         |    Require: 100rel          |
   |                             |         |                             |
   |                             |         |                             |
   |(3) PRACK                    |         |(3) PRACK                    |
   |---------------------------->|         |---------------------------->|
   |                             |         |                             |
   |                             |         |                             |
   |(4) 200 PRACK                |         |(4) 200 PRACK                |
   |<----------------------------|         |<----------------------------|
   |                             |         |                             |
   |                             |         |                             |
   |(5) UPDATE with offer 2      |         |                             |
   |<----------------------------|         |                             |
   |                             |         |                             |
   |                             |         |                             |
   |(6) 200 UPDATE with answer 2 |         |                             |
   |---------------------------->|         |                             |
   |                             |         |                             |
   |                             |         |                             |
   |(7) 200 INVITE               |         |(5) 200 INVITE with offer 2  |
   |<----------------------------|         |<----------------------------|
   |                             |         |                             |
   |                             |         |                             |
   |(8) ACK                      |         |(6) ACK with answer 2        |
   |---------------------------->|         |---------------------------->|
   |                             |         |                             |

             Figure 1-A                             Figure 1-B

IMHU, both of these two processes can solve the same problem whereas in the
process of Figure 1-B, it looks more optimized. Then why this second process
could not be accepted? What possible problem does it cause?

Looking for any comment.

Best regards.

[email-masked] wrote in <[email-masked]>
>If at all you want to propose a *newoffer*,you should use *Update* for the same.
>
>regds,
>srikanth sundaragopalan
>
>I have one question concerning a new offer inclusion during a transaction of