[SIPForum-discussion] SIP TRACE Behaviour

[Garron, James]

Below is from draft-ietf-mmusic-sdp-comedia-10.  /Jim
 
4.  Setup Attribute

   The 'setup' attribute indicates which of the end points should
   initiate the TCP connection establishment (i.e., send the initial TCP
   SYN).  The 'setup' attribute is charset-independent and can be a
   session-level or a media-level attribute.  The following is the ABNF
   of the 'setup' attribute:


         setup-attr           =  "a=setup:" role
         role                 =  "active" / "passive" / "actpass"
                                 / "holdconn"

      'active': The endpoint will initiate an outgoing connection.

      'passive': The endpoint will accept an incoming connection.

      'actpass': The endpoint is willing to accept an incoming
      connection or to initiate an outgoing connection.

      'holdconn': The endpoint does not want the connection to be
      established for the time being.

4.1  The Setup Attribute in the Offer/answer Model

   The offer/answer model, defined in RFC 3264 [5], provides endpoints
   with a means to obtain shared view of a session.  Some session
   parameters are negotiated (e.g., codecs to use), while others are
   simply communicated from one endpoint to the other (e.g., IP
   addresses).  The value of the 'setup' attribute falls into the first
   category.  That is, both endpoints negotiate its value using the
   offer/answer model.

   The negotiation of the value of the 'setup' attribute takes places as
   follows.  The offerer states which role or roles it is willing to
   perform and the answerer, taking the offerer's willingness into
   consideration, chooses which roles both endpoints will actually
   perform during connection establishment.  The following are the
   values that the 'setup' attribute can take in an offer/answer
   exchange:


            Offer      Answer
            ________________
            active     passive / holdconn
            passive    active / holdconn

            actpass    active / passive / holdconn
            holdconn   holdconn

    

 The active endpoint SHOULD initiate a connection to the port number
   on the 'm' line of the other endpoint.  The port number on its own
   'm' line is irrelevant, and the opposite endpoint MUST NOT attempt to
   initiate a connection to the port number specified there.
   Nevertheless, since the 'm' line must contain a valid port number,
   the endpoint specifying using the value active SHOULD specify a port
   number of 9 (the discard port) on its 'm' line.  The endpoint MUST
   NOT specify a port number of zero, except to denote an 'm' line that
   has been or is being refused.

   The passive endpoint SHOULD be ready to accept a connection on the
   port number specified in the 'm' line.

   A value of 'actpass' indicates that the offerer can either initiate a
   connection to the port number on the 'm' line in the answer or accept
   a connection on the port number specified in the 'm' line in the
   offer.  That is, the offerer has no preference as to whether it
   accepts or initiates the connection and, so, is letting the answerer
   choose.

   A value of 'holdconn' indicates that the connection should not be
   established for the time being.

   The default value of the setup attribute in an offer/answer exchange
   is 'active' in the offer and 'passive' in the answer.


 

 From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org]On Behalf Of tharsan thas
Sent: Wednesday, January 28, 2009 12:16 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] SIP TRACE Behaviour



Hi, im quite new to SIP, and still learning.
 
following trace was taken, for a sip call where AUDIO is not working. just wondering, what is the function of the  last line, a=direction:active 
and is there any alternative that i could try. sorry if its a silly question
 
 
v=0
o=- 3539357 3539357 IN IP4 84.215.135.146
s=-
c=IN IP4 84.215.135.146
t=0 0
m=audio 16406 RTP/AVP 8 99 100
a=rtpmap:8 PCMA/8000
a=rtpmap:99 NSE/8000
a=fmtp:99 192-193
a=rtpmap:100 telephone-event/8000
a=fmtp:100 0-15
a=ptime:20
a=sendrecv
a=direction:active
 
Sarm


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