[R-C] REMB message, SSRC list and DiffServ

[Harald Alvestrand]

I just remembered one reason why we put an SSRC list in the REMB 
message, and I don't think we've mentioned this on the list....

If SSRCs get sent with different DiffServ codepoints, they are going to 
experience very different congestion states at intermediate routers. It 
doesn't make sense to give feedback on them jointly or on average.

We don't know yet how we should divide those SSRCs into different 
groups, but it's good to have the ability to do so without changing the 
signalling.

The congestion state on a set of SSRCs should only be applied as a basis 
for controlling traffic over the set of data that is sent with the same 
DiffServ markings.
(Grammar bad. I beg forgiveness, and hope the meaning carries.)

                    Harald