Media friendly rate control mfrc
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Media Friendly Rate Control (MFRC). draft-phelan-mfrc-00.txt Tom Phelan – Sonus Networks 6-August-2004 Agenda. Background Thought Process MFRC Basics Next Steps. Background.

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Media Friendly Rate Control (MFRC)

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Media friendly rate control mfrc

Media Friendly Rate Control (MFRC)


Tom Phelan – Sonus Networks




  • Background

  • Thought Process

  • MFRC Basics

  • Next Steps



  • 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

Thought process

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

Thought process1

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

Mfrc basics

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

Mfrc basics1

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

Mfrc basics2

MFRC Basics

  • Recovery phase:

    • Allowed rate variations based on TFRC

    • Return to uncongested phase when TFRC allowed rate equals connection max rate

Next steps

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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