Hi,
Kasturi>>>When PRACK is supported the offer/answer completes on the first
Answer (18x). Subsequently if you include it in 200 ok, it can be treated as
a new offer. Depends on whether the UAC is ready to receive it and treat it
as an offer. If it treats it as an offer it can respond with answer in ACK.
-------------
There should be at most one offer/answer per transaction.Please refer the following link.
http://www1.ietf.org/mail-archive/web/sip/current/msg11956.html
http://tools.ietf.org/wg/sip/draft-sawada-sipping-sip-offeranswer-00.txt
-------------
vinodh kumar>>> You cannot Send SDP(answer) in a response that is not reliable, for the simple reason you don't get the Acknowledgement whether the offerer has received it or not. The offer/answer model in SIP mandates that the answer be received reliably.
-------------
Offer can not be in the non-reliable provisional responses. But Answer can be in the non-reliable provisional responses.
>From RFC 3261
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.
-------------
Regards,
Thangarajan.
FlextronicsSoftware
Worlds largest SIP stack vendor
"Kasturi Narayanan" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED] 02/02/2006 11:13 PM |
|
Comments in line
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]] On Behalf Of Andreas
Byström
Sent: Thursday, February 02, 2006 6:32 AM
To: [email protected]
Subject: [Sip-implementors] Offer/answer retransmission OK?
Hi I have two SDP questions:
1. Is it (according to RFCs) ok to send the SDP answer in a SIP response
that is not reliable? I.e, is it ok to send SDP in 180 (that is not using
PRACK)
Kasturi>>>>Yes it is ok to send SDP (Answer) in 18x messages regardless of
whether prack is supported.
2. If sent in 180 (as above) is it then ok to send the exact same response
again in 200 OK?
Kasturi>>>Yes it needs to be repeated in 200 ok.
Is it allowed to respond to a offer in two different
mesages (first 180 and then 200).
Kasturi>>>Yes, but should be the same.
Does it matter if 180 is reliable (say
that PRACK is used for 180, still ok to send SDP answer in 200?)
Kasturi>>>When PRACK is supported the offer/answer completes on the first
Answer (18x). Subsequently if you include it in 200 ok, it can be treated as
a new offer. Depends on whether the UAC is ready to receive it and treat it
as an offer. If it treats it as an offer it can respond with answer in ACK.
Kastur>>>Even when PRack is supported it is not mandatory to return answer
in 18x and can always be sent in 200 ok.
Regards,
// Andreas
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