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Media Friendly Rate Control (MFRC)

Media Friendly Rate Control (MFRC). draft-phelan-mfrc-00.txt Tom Phelan – Sonus Networks tphelan@sonusnet.com 6-August-2004 http://www.phelan-4.com/dccp/DCCP-MFRC-SanDiego.ppt. Agenda. Background Thought Process MFRC Basics Next Steps. Background.

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Media Friendly Rate Control (MFRC)

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  1. Media Friendly Rate Control (MFRC) draft-phelan-mfrc-00.txt Tom Phelan – Sonus Networks tphelan@sonusnet.com 6-August-2004 http://www.phelan-4.com/dccp/DCCP-MFRC-SanDiego.ppt

  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?

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