[Iccrg] Re: Iccrg Digest, Vol 80, Issue 3

[Arjuna Sathiaseelan]

Hello Cheng,
 Check out the new-cwv draft that addresses the app-limited problem:
http://tools.ietf.org/html/draft-fairhurst-tcpm-newcwv-04

This draft has some major issues and we have got a new version which
is much more stable and will be submitted to ICCRG soon..

Regards
Arjuna

On 8 September 2012 12:01,  <iccrg-request at cs.ucl.ac.uk> wrote:
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>    1. Re: [tcpm] RFC5681: why halving FlightSize not cwnd?
>       (Yuchung Cheng)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 7 Sep 2012 15:49:01 -0700
> From: Yuchung Cheng <ycheng at google.com>
> Subject: [Iccrg] Re: [tcpm] RFC5681: why halving FlightSize not cwnd?
> To: gorry at erg.abdn.ac.uk
> Cc: "tcpm at ietf.org Extensions" <tcpm at ietf.org>, "iccrg at cs.ucl.ac.uk
>         list" <iccrg at cs.ucl.ac.uk>
> Message-ID:
>         <CAK6E8=cCZJgg9N8EVGu5LtC_-Du9ZZx0Qv5_j3zjZ0d72eqztQ at mail.gmail.com>
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>
> I am glad we all identify the problem about FlightSize. We need a
> better mechanism to address application-limited cases, i.e., when cwnd
> is not fully used recently.
>
> within an RTT or so:
> a) loss: halve cwnd or flightsize or something else?
> b) no-loss: grow cwnd or not?
>
> longer than several RTTs (idle)
> c) decay the cwnd every couple minutes or every couple RTO, slow-start
> to prev cwnd, blah?
>
> There is always a concern about potential bursts leaving cwnd >>
> FlightSize. So RFCs and implementations drag cwnd to "moderate"
> potential bursts. For example, Linux pulls cwnd down to FlightSize +
> epsilon whenever an ACK does not look right, and refuses to grow cwnd
> unless it was fully used. And most congestion control design does not
> consider these events.
>
> I don't know what the right solution is yet. Pacing + track inflight
> of last RTT?
>
> but I know app-limited cases happen a whole lot today. Beside HTTP or
> RPCs (in data centers), even video deliveries are interactive, e.g.,
> NetFlix or Youtube. The apps pace at second(s) interval to conserve
> network bandwidth. And TCP-smart apps all use persistent connections
> today. TCP usage has moved away from bulk-ftp long time...
>
> Yuchung
>
>
>
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> End of Iccrg Digest, Vol 80, Issue 3
> ************************************