Colin, What do you mean by SSRC space, can you share me with an example? I think SSRC just identify a stream. And each RTP session is able to include several streams. thanks Regards, -Rockson ________________________________
From: Colin Perkins [mailto:[EMAIL PROTECTED] Sent: Saturday, November 29, 2008 4:25 AM To: Rockson Li (zhengyli) Cc: [email protected]; [EMAIL PROTECTED] Subject: Re: [AVT] how to identify a RTP session The basic idea is that if the participants share a single SSRC space, they form a single RTP session. Colin On 28 Nov 2008, at 03:48, Rockson Li (zhengyli) wrote: Hi folks, Recently, I am confused on the identity of a RTP session. per RFC3550 RTP session: An association among a set of participants communicating with RTP. ... A participant distinguishes multiple RTP sessions by reception of different sessions using <NOTE>different pairs of destination transport addresses,</NOTE> where a pair of transport addresses comprises one network address plus a pair of ports for RTP and RTCP. So I draw the conclusion as follows, a RTP session is identified as a network plus two destination ports(RTP && RTCP port). therefore suppose two SIP UAs taking with each other on unicast UDP. UA1 UA2 IP: ip1 IP: ip2 RTP port: port1 RTP port: port2 RTCP port: port1+1 RTCP port: port2+1 so there will be two destination paris (ip1+ (port1,port1+1)), (ip2+(port2,port2+1)) so based on definition above, this should be thought as two RTP sessions, shouldn't it? However, the same section of RFC3550. <snip> For example, consider a three- party conference implemented using unicast UDP with <NOTE>each participant receiving from the other two on separate port pairs.</NOTE> If each participant sends RTCP feedback about data received from one other participant only back to that participant, then the conference is composed of three separate point-to-point RTP sessions. </snip> why there're only three RTP sessions, I think it should be six? since "each participant receiving from the other two on separate port pairs" which means each pariticipant should listen on two separate port paris for incoming RTP packets, so there're two RTP sessions for each participant, and should be six for three participants. Confunsed.... any ideas? thanks Regards, -Rockson _______________________________________________ Audio/Video Transport Working Group [EMAIL PROTECTED] https://www.ietf.org/mailman/listinfo/avt -- Colin Perkins http://csperkins.org/ _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
