Subject: [tcpm] new ID on RTO considerations

From: Mark Allman <[email-masked]>
Date: Mon, 07 Mar 2011 09:29:51 -0500

Folks-

For a while I have been thinking maybe what we need is some high-level
guidance on the RTO and to then leave it at that instead of worrying
about nitty-gritty specifics that really don't much matter.  This has
bubbled up to the top of my brain recently based on a few different
conversations.  So, last week I spent a little time bloviating into an
emacs buffer.  See draft-allman-tcpm-rto-consider-00.txt .  Its rough,
but I hope gets the idea across.

I have no idea if this is something the WG might want to pursue, but
feedback is certainly welcome.

allman

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From: Yuchung Cheng <[email-masked]>
Date: Tue, 8 Mar 2011 16:21:05 -0800

I like this draft but the MUST on exp backoff may be too strict.

Research study has argued the exp-backoff is not needed.
http://blue.cs.northwestern.edu/~akm175/docs/extr.pdf

In practice, Linux implements TCP thin-stream that does linear-backoff to
improve online game performance (by default off)
http://heim.ifi.uio.no/paalh/publications/files/lcn08-thin.pdf

Yuchung
<http://blue.cs.northwestern.edu/~akm175/docs/extr.pdf>

On Mon, Mar 7, 2011 at 6:29 AM, Mark Allman <[email-masked]> wrote:

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From: Mark Allman <[email-masked]>
Date: Wed, 09 Mar 2011 11:03:56 -0500

> http://heim.ifi.uio.no/paalh/publications/files/lcn08-thin.pdf

I am aware of the first, but not the second.  I glanced through it and
will endeavor to look into it further.

However, I'll note that I am disinclined to remove exponential backoff
From the guidelines based on a couple of simulation / testbed studies no
matter what they say.  It seems that we'd want to be quite careful
before we decided that was not required as that seems like our ultimate
backstop.

Plus, ... its hard to imagine that backoff really hurts in some
meaningful way.  Once you have RTOed twice your performance is likely
gone.  And, you have had multiple indications the network is congested.
So, its hard for me to buy the removal of this.  And, especially so in
the absence of any sort of empirical understanding.

allman