netdev - Re: [PATCH] make _minimum_ TCP retransmission timeout configurable

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Message-ID: <20070829155106.43cf69eb@freepuppy.rosehill.hemminger.net>
Date:	Wed, 29 Aug 2007 15:51:06 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	ian.mcdonald@...di.co.nz, rick.jones2@...com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] make _minimum_ TCP retransmission timeout configurable

On Wed, 29 Aug 2007 15:28:12 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: Stephen Hemminger <shemminger@...ux-foundation.org>
> Date: Wed, 29 Aug 2007 15:13:01 -0700
> 
> > There was some discussion about implementing TCP NCR (RFC4653)
> > and Narasimha Reddy said he might have something that could be used.
> 
> Although this looks interesting, I'm unsure it will help these
> cell folks.  Actually I can't tell for sure until Rick provides
> us with some more details of the exact issue at hand.
> 
> NCR seems to deal with when the trigger loss recovery, whereas
> the cell phone network folks aparently want to jack up TCP_RTO_MIN
> so that hard timeout based retranmits are deferred a lot more
> than normal.
> 
> And reading NCR some more, we already have something similar in the
> form of Alexey's reordering detection, in fact it handles exactly the
> case NCR supposedly deals with.  We do not trigger loss recovery
> strictly on the 3rd duplicate ACK, and we've known about and dealt
> with the reordering issue explicitly for years.
> 

Yeah, it looked like another case of BSD RFC writers reinventing
Linux algorithms, but it is worth getting the behaviour standardized
and more widely reviewed.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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