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Date: Mon, 23 Feb 2004 23:40:17 -0600 (CST)
From: Mike Silbersack <silby@silby.com>
To: "Ronald F. Guilmette" <rfg@monkeys.com>
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cc: freebsd-net@freebsd.org
Subject: Re: default socket receive buffer size, net.inet.tcp.recvspace (?)
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On Mon, 23 Feb 2004, Ronald F. Guilmette wrote:

> I have just now found out that the kernel default value for
> net.inet.tcp.recvspace, i.e. the default amount of receive
> buffer space associated with a new socket is set to 56kB,
> at least on the specific version of FreeBSD (4.7) that I'm
> running.
>
> Just curious:  why?
>
> 56kB seems like a somewhat odd number to pick for the default.
>
> Why not 32kB or else 64kB?

Because once you hit 64K, you need to use TCP window scaling, and older
versions of IPFilter had problems with window scaling.  Once this was
discovered, the value was reduced to 56K.  I think that IPFilter was
updated and the value was changed back, but I don't recall exactly.

Mike "Silby" Silbersack