Does anyone have a clue about multicast and the questions below?
Any help would be greatly appreciated.
Regards,
Attila
-----Original Message-----
From: Attila Sipos
Sent: 17 May 2007 17:30
To: Sip-implementors@cs.columbia.edu
Subject: [Sip-implementors] RFC 3264 offer/answer - multicast
I have some questions on section 5.2:
5 Generating the Initial Offer
5.2 Multicast Streams
If a session description contains a multicast media stream which is
listed as receive (send) only, it means that the participants,
including the offerer and answerer, can only receive (send) on that
stream. This differs from the unicast view, where the directionality
refers to the flow of media between offerer and answerer.
I am confused about this. It seems to say that if the offer has recvonly
then both the "offerer and answerer" can only receive on that port.
I am sure my interpretation is wrong -
what is the correct interpretation?
=========================
Also regarding, "6.2 Multicast Streams", generating the answer, it seems
that if the offer was a multicast SDP, the answer has to be an almost identical
mulicast SDP. Fine. But what happens if the offer was unicast and the
desired answer is multicast?
For example, if you sent an INVITE to a server with unicast
but the server wanted to use multicast to send the same RTP to
everyone, can this happen?
Would there need to be anything special in the SDP?
=========================
And who is allowed to send (say RTP) to a multicast IP address?
Surely it only makes sense that the server sends the multicasts
while the clients keep quiet. ??
Regards,
Attila
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