[SIPForum-discussion] Regarding 491 request pending

Garron, James jgarron at sonusnet.com
Mon Oct 1 14:39:02 UTC 2012

Was the 183 sent reliably?

If the UPDATE is being sent before the completion of the INVITE transaction, and the initial INVITE contained an offer, the UPDATE cannot be sent with an offer unless the callee has generated an answer in a reliable provisional response, has received a PRACK for that reliable provisional response, has not received any requests (PRACK or UPDATE) with offers that it has not answered, and has not sent any UPDATE requests containing offers that have not been answered.

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Prem chandiran
Sent: Friday, September 28, 2012 4:59 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Regarding 491 request pending

Hi All,

may i know why 491 request pending is sent for UPDATE, as per rfc 33 11 "If an UPDATE is received that contains an offer, and the UAS has generated an offer (in an UPDATE, PRACK or INVITE) to which it has not yet received an answer, the UAS MUST reject the UPDATE with a 491 response." below is the call flow

| |
| INVITE(with offer) |
------------------------------------------> |
| |
| 100 Trying |
| |
| 183 (with Answer) |
| |
| UPDATE(With Offer) |
| |
| 491 Request Pending |
------------------------------------------> |

UA sends an offer in invite for that UA1 respond with answer in 183 then UA1 triggers UPDATE with offer UA is sending 491. Please let me know what might be wrong.

Thanks all...

Prem Chandiran
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