netdev - Why is tcp_reno_min_cwnd() ssthresh/2?

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Date:	Thu, 3 Apr 2008 17:00:04 -0800
From:	"Lachlan Andrew" <lachlan.andrew@...il.com>
To:	Netdev <netdev@...r.kernel.org>
Subject: Why is tcp_reno_min_cwnd() ssthresh/2?

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

-- 
Lachlan Andrew  Dept of Computer Science, Caltech
1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA
Ph: +1 (626) 395-8820    Fax: +1 (626) 568-3603
http://netlab.caltech.edu/lachlan
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