[SIPForum-discussion] Regarding 491 request pending

[Santosh Iyer]

Technically only the UAC can generate an UPDATE, an UAS cannot. UAC generates anUPDATE to update the offer. even the excerpt that you have pasted from rfc 3311 implies that a UAC generated the UPDATE and the UAS generated the answer. Hope that answers your question

--- On Sat, 9/29/12, Prem chandiran <toprem.m at gmail.com> wrote:

From: Prem chandiran <toprem.m at gmail.com>
Subject: [SIPForum-discussion] Regarding 491 request pending
To: discussion at sipforum.org
Date: Saturday, September 29, 2012, 2:29 AM

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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