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From: Stephen Hemminger <shemminger@vyatta.com>
To: "John Heffner" <johnwheffner@gmail.com>,
	"Lachlan Andrew" <lachlan.andrew@gmail.com>
Cc: "Xiaoliang David Wei" <davidwei79@gmail.com>,
	Netdev <netdev@vger.kernel.org>
Subject: Re: Why is tcp_reno_min_cwnd() ssthresh/2?
Date: Fri, 4 Apr 2008 11:31:14 -0700	[thread overview]
Message-ID: <20080404113114.2181a146@extreme> (raw)
In-Reply-To: <1e41a3230804040924q34d009c9w97dded92f13392dc@mail.gmail.com>

> Greetings all,
> 
> Apologies if this is a dumb question, but why does
> tcp_reno_min_cwnd()  return  ssthresh/2?
> 
> Since   ssthresh <- snd_cwnd/2   on loss, this looks like it tries to
> reduce  snd_cwnd  to 1/4 its value before a loss event, presumably
> then slow-starting back to half of the original  snd_cwnd.
> 
> As Tom Quetchenbach pointed out, it is also odd that  omitting
> min_cwnd()  from a congestion control module causes  ssthresh  to be
> used, giving different results from using  tcp_reno_min_cwnd().
> 
> Thanks,
> Lachlan

First sighed 5 years ago, and every times it comes up, the original
behaviour is retained.

http://oss.sgi.com/archives/netdev/2003-01/msg00114.html

  reply	other threads:[~2008-04-04 18:31 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-04-04  1:00 Why is tcp_reno_min_cwnd() ssthresh/2? Lachlan Andrew
2008-04-04  2:35 ` Xiaoliang "David" Wei
2008-04-04 16:24   ` John Heffner
2008-04-04 18:31     ` Stephen Hemminger [this message]
2008-04-04 19:27       ` Lachlan Andrew

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