1. Media Friendly Rate Control (MFRC)
draft-phelan-mfrc-00.txt
Tom Phelan – Sonus Networks
6-August-2004

2. Agenda
Background
Thought Process
MFRC Basics
Next Steps

3. Background
Mailing list discussions show difficulties with TFRC and interactive media
You can put the square peg in the round hole, but something less brutish would be nice
Draft is a thought-experiment exploration of possible solution areas
Intention is to stimulate discussion
Could be first step on (long) path to solution

4. Thought Process TFRC congestion reaction pretty much OK
Smooth rate reduction, cautious rate increase
Biggest problems involve TFRC “congestion avoidance” mechanisms
Slow start, restart, rate variation restrictions
Necessary for file transfer apps

5. Thought Process
Media apps today have other congestion avoidance mechanisms
Client/server pick max rate based on knowledge of access link speeds
Simple, works most of the time
Most of the time, TFRC congestion avoidance redundant
So, why not let media apps guess at non-congesting rate, then react if the guess is wrong?
That’s MFRC

6. MFRC Basics Three operational phases Uncongested phase:
Connections start here
Free variation of transmit rate up to maximum set at connection start
Yah, issues here 
Exit to congested phase with packet loss

7. MFRC Basics Congested phase:
Halve allowed rate for each RTT with packet loss
No allowed rate increases
Exit to recovery phase after congestion dissipates – a number of RTTs with no packet loss

8. MFRC Basics Recovery phase: Allowed rate variations based on TFRC
Return to uncongested phase when TFRC allowed rate equals connection max rate

9. Next Steps Mailing list discussion stimulated new ideas
Restart bigger problem than slow start
Byte rate better than packet rate
Better to allow rate variations in all phases
Simulate! – Anyone willing to help?
Where’s the home for this work?
dccp, tsvwg, avt, something else?