[MMUSIC] RFC 6190 Single Session Transport

[Bernard Aboba <[e-mail]>]

At the virtual interim, a question arose about RFC 6190 Single Session Transport. 
Here is what RFC 6190 Section 1 says:
   This memo defines two basic modes for transmission of SVC data,
   single-session transmission (SST) and multi-session transmission
   (MST).  In SST, a single RTP session is used for the transmission of
   all scalability layers comprising an SVC bitstream; in MST, the
   scalability layers are transported on different RTP sessions. Section 1.2.2 clarifies the usage scenarios of SST and MST: 
   SST should be used in point-to-point unicast applications and, in
   general, whenever the potential benefit of using multiple RTP
   sessions does not justify the added complexity...  

   MST should be used in a multicast session when different receivers
   may request different layers of the scalable bitstream.  Since SST implies (by definition), use of a single RTP session to transport multiple layers, were plan A to be used for signaling, negotiation of SST would only be possible if both peers support BUNDLE, since otherwise distinct RTP ports would be required for each layer, which is incompatible with SST.    Today, existing SST implementations typically utilize a single m line.  As Jonathan noted, some implementations utilize the same SSRC for multiple layers, while others utilize distinct SSRCs.  Utilization of the same SSRC is possible, since separation of the layers can be handled within the H.264/SVC implementation.