SIP and H.323 Interworking question

Hemant Agrawal hemantag at globespan.net
Thu Sep 14 07:08:02 EDT 2000


Hi Paul
          SDP used by SIP contains the connection address in the 'c=' line,
         while it contains the RTP port information in 'm = ' line.  the
RTCP port used will be RTP port +1

                    c=<network type> <address type> <connection address>
                    m=<media> <port> <transport> <fmt list>

         The call originator will sends it's RTP port information &
connection address in the INVITE message, and it will get the other end  RTP
port info & connection address in the response ( e.g.200 OK).


Thanks  & Regards,
Hemant Agrawal




> Folks,
>
> I was recently pondering issues related to H.323/SIP interworking--
> particularly the handling of media streams.
>
> If I understand things correctly, the 'm=' line in the SDP used by SIP
> indicates only the media address to which RTP packets will be sent.  It
says
> nothing about the RTP/RTCP port used for sending media.  Those can be
> another pair of ports, apparently.
>
> How, then, can an H.323 IWF send an OLC to an H.323 endpoint?  (Let's
assume
> that the IWF does not want to proxy the media-- only handle signaling.)
>
> Assume that the IWF has received the INVITE message, containing the RTP
> address of the reverse channel.  It then goes ahead and establishes the
call
> with the H.323 endpoint, starts H.245 and exchanges capability
information.
>
> Suppose the IWF now wishes to open a channel.  Part of the
> forwardLogicalChannel parameters of the OLC is a required field called
> "mediaControlChannel".  However, this information is not passed in the
SDP.
>
> Are people assuming, as I had done, that the 'm=' line contained the RTP
> address for both sending and receiving media?
>
> Am I misreading something or is there a real interworking issue here?
>
> Thanks,
> Paul
>
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