[SIPForum-discussion] What's the info contained in the SDP?

[Mike Jiang]

 Hi, All

      I have a quick question: when I make a call from a SIP phone, the SIP
server sends 183 Session Process, 180 Ringing, and 200 OK msgs sequentially
back 

 to the phone. Usually at least one of three above has the SDP as the body.
The SDP contains the info about the IP, port, and audio codecs of the
target. My question is: is the IP/port that of the SIP Server or the
callee's phone? The reason why I ask this is: the SIP phone only talks with
the SIP server directly, then the SIP server manages to relay voice packets
to the callee. As for how the SIP server routes the call to the callee,
that's not the business the SIP phone cares.  So I think the IP/Port in SDP
is that of the SIP server rather than the callee's phone. The SIP server
provider told me it's the callee's. I got confused.

 

      Thanks for any input,

 

      Mike J.

 

 

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