[SIPForum-discussion] [Sip-implementors] Offer in a 200OK for Invite transaction.

[Manpreet Singh]

Chris

This answer was very helpful.

So even when 18x carries the answer, till its reliable, the offer/answer is
not complete. Which means 200OK MUST carry the same answer again to complete
the offer/answer. So the 200OK SDP in this case would really be treated more
as an answer needed to complete the offer/answer for INVITE transaction and
both these answers MUST be identical right? Otherwise it would confuse the
UAC.

Somesh, it will only ignore other responses if the 18x was reliable. But if
was not then it will expect the same answer to be followed in the 200OK to
complete the offer/answer for that transaction.

Manpreet

-----Original Message-----
From: Christer Holmberg (JO/LMF) [mailto:christer.holmberg at ericsson.com] 
Sent: Wednesday, July 19, 2006 5:43 PM
To: someshss at yahoo.com; Manpreet Singh; discussion at sipforum.org
Cc: sip-implementors at cs.columbia.edu
Subject: RE: [Sip-implementors] [SIPForum-discussion] Offer in a 200OK
forInvite transaction.


Hi,

An unreliable 18x does not complete the offer/answer transaction (eventhough
you know what the answer is), so you can't send an new offer at that point.

Also, even if the 18x would be sent reliably, and complete the offer/answer
transaction, you can not send a new offer in the 200 OK. You can have at
most one offer/answer transaction per SIP transaction.

Regards,

Christer
 

-----Original Message-----
From: sip-implementors-bounces at cs.columbia.edu
[mailto:sip-implementors-bounces at cs.columbia.edu] On Behalf Of Somesh S
Shanbhag
Sent: 20. heinäkuuta 2006 0:27
To: Manpreet Singh; discussion at sipforum.org
Cc: sip-implementors at cs.columbia.edu
Subject: Re: [Sip-implementors] [SIPForum-discussion] Offer in a 200OK
forInvite transaction.

Hi Manpreet,
  
  RFC 3261 section 13.2.1 has the following clause ...
  
  "
  
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 "

So, UAC MUST treat 183 session progress as the answer and shall ignore in
subsequent responses to INVITE.

Hope this helps
Thanks
Somesh S. Shanbhag

  

Manpreet Singh <msingh at ibasis.net> wrote:              For the INVITE
transaction where the offer was sent in an INVITE and the answer coming back
in   183, would it be valid to send a new offer in the 200OK? So the
question is   whether the 200OK can be used to send a "new" Offer (
different from the answer   in 183 ) for the INVITE transaction once 183 has
completed the offer/answer   part of that transaction. Only UPDATE can be
used for early dialog changes as   per my understanding and a 200OK still
constitutes early dialog so it wont   be valid to send a new offer in 200OK?
Although 200OK can carry the same SDP as   183 which would mean nothing or
would not be considered as early dialog change   in capability.
   
  Please correct me if   I am wrong.
   
  Thanks
   
  Manpreet   
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BE NATURAL LIVE NATURAL.
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Somesh S. Shanbhag
Focus Area - VoIP Team (FA-VoIP)
Mascon Global Communication Technologies Enterprise of Mascon Global Limited
#59/2, 100Ft Ring Road Banashankari II stage Bangalore-560070 Karnataka
INDIA
Website: http://www.mgl.com/
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