[R-C] Why not TFRC?

[Piers O'Hanlon]

HI,

I thought it would be useful to understand what people consider are
the problems with TFRC, and why they mean a new congestion protocol
would be better for RTCweb?

Clearly TFRC does have some issues though it would be useful for the
community to understand why TFRC needs to be superseded? Given that it
is probably the most widely cited standard for real-time media flows
and appears to have a growing number of 'TFRC based' deployments: e.g.
GoogleTalk says it is 'based upon TFRC', Gnome's Empathy IM/videoconf
client has recently put TFRC support into their Farsight library, and
others (Magor etc) who mentioned their use of it on RTCweb.

I guess I can start with a few well known issues with TFRC:
- Problems with clocking the packets out for TFRC
- Issues with using variable packet sizes
- "Very low video bitrates at moderate loss rates" 3GPP tr26.114
- 'Oscillatory behaviour'

Once a few of these are clear one would expect the new offering(s)
would need to show they can demonstrate improvement in these areas.

Piers O'Hanlon