Re: [Sip-implementors] Some Questions on use of UPDATE method

Paul Kyzivat Wed, 28 Jan 2004 12:04:46 -0800

[EMAIL PROTECTED] wrote:

Comments inline…

-----Original Message----- *From:* [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] *On Behalf Of *Attila Sipos *Sent:* Wednesday, January 28, 2004 12:46 PM *To:* Ranjit Avasarala (WT01 - TELECOM & INTER-NETWORKING SOLUTIONS); [EMAIL PROTECTED]; [EMAIL PROTECTED] *Cc:* [EMAIL PROTECTED] *Subject:* RE: [Sip-implementors] Some Questions on use of UPDATE method
I agree that I don't think you can send an UPDATE to answer an INVITE.
However, UPDATE can be used to change session/media BEFORE
an INVITE/200 OK. Otherwise you could just use re-INVITE's.
*/ /*

*/ [ABN] /*in this case functionality of both re-Invite and UPDATE are similar but the actual difference lies where UPDATE is always one way whereas in re-invite the negotiation happens like initial invite request. In UPDATE, either offer is accepted or ignored but the entity which receives UPDATE can’t send it’s allowed media parameters in the response, like what happens in 200OK for INVITE or re-INVITE.

Huh? Are you suggesting that if an UPDATE carries and offer, the response to the update doesn't carry an answer? That makes no sense - offers and answers always come in pairs.

Or are you simply saying that UPDATE cannot be used to replace the invite form that carries no offer and instead solicits the UAS to send an offer in a response? If so then I agree.

Paul

From Abstract of RFC 3311 (UPDATE RFC) -

....UPDATE allows a client to update parameters of a session (such as the set of media streams and their codecs) but has no impact on the state of a dialog. In that sense, it is like a re-INVITE, but unlike re-INVITE, it can be sent before the initial INVITE has been completed. This makes it very useful for updating session parameters within early dialogs.

Regards,

Attila
    -----Original Message-----
    *From:* [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
    *Sent:* 28 January 2004 04:43
    *To:* [EMAIL PROTECTED]; [EMAIL PROTECTED]
    *Cc:* [EMAIL PROTECTED]
    *Subject:* RE: [Sip-implementors] Some Questions on use of UPDATE method
    I don't think u can send UPDATE to answer a INVITE. UPDATE is used
    to change session / media parameters after INVITE/200 OK.
    Ranjit
    Ph: 8520408/16 extn: 2173
        -----Original Message-----
        *From:* [EMAIL PROTECTED]
        [mailto:[EMAIL PROTECTED] *On Behalf Of
        *Kasammiya Patil
        *Sent:* Tuesday, January 27, 2004 8:36 PM
        *To:* [EMAIL PROTECTED]
        *Cc:* [EMAIL PROTECTED]
        *Subject:* [Sip-implementors] Some Questions on use of UPDATE method
Hi,

I have couple of questions regarding the use of UPDATE method.
        1. Can UPDATE be used to send an answer SDP ?
            Consider the following scenario:
            -  INVITE was sent without SDP
            - 18x is received with Offer SDP
            - There is no PRACK exchange because 18x does not contain a
        Require:100rel header
            Now can UPDATE be used to send answer SDP??
        2. As per RFC 3311, UPDATE method should be used only if dialog
        is established.
            If INVITE/18x exchange happened without PRACK, can both ends
        treat this as early dialog and feel free to use UPDATE ?
        3. Is 18x send/recv over TCP considered reliable ?
            In the following scenario:
            - INVITE with offer sdp sent
            - 18x over TCP with answer sdp recvd (No PRACK exchange
        happened)
            Now can the caller/calleee use UPDATE ?
Appreciate any responses. Thanks, Kasam

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Re: [Sip-implementors] Some Questions on use of UPDATE method

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