SIP Messages and Media Session

Discussion in 'VOIP' started by Anast, Aug 6, 2004.

  1. Anast

    Anast Guest

    Hi all,

    Suppose we have two SIP UAs that one invites the other, then they
    start a media session and then the connection is terminated. How
    exactly the media session is being terminated? I mean, one of the UA
    terminates the Media Session and then sends a BYE SIP message to the
    other party; or once the media session is opened and the UA decide to
    close it will send first a BYE message and then will close the media
    session?

    Option 1.

    UA1 UA2
    |-----------> INVITE
    <-----------| 100 TRYING
    <-----------| 180 RINGING
    <-----------| 200 OK
    |-----------> ACK

    |-----------> Open Media Session
    |-----------> Close Media Session

    |-----------> BYE
    <-----------| 200 OK


    or......
    Option 2.

    UA1 UA2
    |-----------> INVITE
    <-----------| 100 TRYING
    <-----------| 180 RINGING
    <-----------| 200 OK
    |-----------> ACK

    |-----------> Open Media Session
    |-----------> BYE
    |-----------> Close Media Session
    <-----------| 200 OK


    Thank you very much in advance.
     
    Anast, Aug 6, 2004
    #1
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  2. In article <>,
    Anast <> wrote:
    >Hi all,
    >
    >Suppose we have two SIP UAs that one invites the other, then they
    >start a media session and then the connection is terminated. How
    >exactly the media session is being terminated? I mean, one of the UA
    >terminates the Media Session and then sends a BYE SIP message to the
    >other party; or once the media session is opened and the UA decide to
    >close it will send first a BYE message and then will close the media
    >session?



    Media sessions are RTP streams over UDP, so they don't really "close"
    in the way TCP sockets do. You just stop sending or stop listening.

    But yes, in a typical flow, the phone that hangs up sends BYE and
    stops sending (and possibly stops listening to) the RTP media stream.

    The other phone gets the BYE, and similarly stops, and sends an OK.

    (The first phone probably should also wait for the OK before it stops
    listening, and possibly even sending.)

    UDP packets don't have connections. If nobody is listening they just
    vanish in a poof like a Jaffa against the Iris. Nobody knows they
    didn't get received.
    --
    Support "Canadians for Global Warming"
    http://www.templetons.com/brad/cfgw.jpg
     
    Brad Templeton, Aug 6, 2004
    #2
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