[SIPForum-discussion] Regarding 491 request pending

[Kashif Husain]

I think your scenario is according to the following section of rfc 3311:


for the callee
      o  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.

Please check the example call flow section of the rfc. If 183 is RPR then
you should not get 491 here. Here is another snippet:

It is important
   to note that a reliable provisional response will always create an
   early dialog at the UAC.  Creation of this dialog is necessary in
   order to receive UPDATE requests from the callee.


Thanks,
-kashif

On Sat, Sep 29, 2012 at 2:29 AM, Prem chandiran <toprem.m at gmail.com> wrote:

> 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
>
> UA UA1
> | |
> | 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...
>
> Regards,
> Prem Chandiran
>
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