[EMAIL PROTECTED] wrote:
In this call flow I don't think it is correct to send session description in
180. As per the two statements below **reliable non-failure message** 183
completed the offer/answer exchange, so resending answer is incorrect.
Oh, I missed that the 180 wasn't reliable. (Its hard to be sure what is
intended without the actual messages, but no prack is shown for it, so I
guess it isn't.)
Yeah, if it isn't reliable, then it shouldn't have SDP.
Paul
RFC 3261, section 13.2.1:
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**.
RFC 3262, section 5:
All user agents that support this extension MUST support all offer/answer
exchanges that are possible based on the rules in Section 13.2 of RFC 3261,
based on the existence of INVITE and PRACK as requests, and 2xx and **reliable
1xx as non-failure reliable responses**.
As per the statement below from RFC3261, section 13.2.1, sending an offer is
incorrect.
"Once the UAS has sent or received an answer to the initial offer, it MUST NOT
generate subsequent offers in any responses to the initial INVITE."
-Ramakrishna
________________________________
From: [EMAIL PROTECTED] on behalf of Neeraj Jain
Sent: Sat 10/1/2005 10:49 AM
To: 'Sip-Implementors'
Subject: RE: [Sip-implementors] Query regarding 183 provisional response.
Please see inline comments.
Neeraj Jain
BayPackets Technologies
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of jay prakash
dubey
Sent: Friday, September 30, 2005 12:26 PM
To: Sip-Implementors
Subject: [Sip-implementors] Query regarding 183 provisional response.
Hi all,
I am having one basic doubt in Prvisional response.If 180 ringing and 183
session progress both came from UAS to UAC.
-----------INVITE+SDP------------------->
<----------183 Session progress(SDP)---------
------------PRACK----------------------->
<------------180 Ringing(SDP)----------------
<------------200 Ok (for PRACK)---------------
<------------200 Ok (for INVITE)--------------
-------------------- --------------ACK( for Invite)---------->
1. what happen if 200 Ok for PRACK doesn"t recieve.call droped or not?
[NEERAJ] UAS in this flow is violating RFC3262 which says that a UAS must
not respond with final response to INVITE until there is an outstanding
provisional response containing SDP (which is 180 Ringing in this case).
Hence 200 Ok (for INVITE) must not be sent before the PRACK is received for
180 Ringing.
2. if 183 and 180 both has SDP than when final SDP negotiation can be done
in 200 OK (PRACK)?
[NEERAJ] Again as per RFC3262, SDP in 180 must be same as that in 183 unless
PRACK (183) contains additional offer from UAC. In later case, 180 must have
the same SDP as 200 OK (PRACK).
can any body clarify this call flow as in my application Early media is
must....
Thanks and regards
Jay
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