From owner-freebsd-bugs  Fri Apr 13  8:22:32 2001
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X-Mailer: exmh version 2.3.1 01/19/2001 with nmh-1.0.4
To: Julian Elischer <julian@elischer.org>
Cc: Toni SOUEID <djt2000@inco.com.lb>, freebsd-bugs@FreeBSD.ORG,
	freebsd-net@FreeBSD.ORG
Subject: Re: Problem in TCP initialisation of cwnd 
In-Reply-To: <3AD711EE.EEADD293@elischer.org> 
References: <000901c0c422$bd356860$941f7ec2@hamster> <3AD711EE.EEADD293@elischer.org>
Comments: In-reply-to Julian Elischer <julian@elischer.org>
   message dated "Fri, 13 Apr 2001 07:49:18 -0700."
From: bmah@cisco.com (Bruce A. Mah)
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If memory serves me right, Julian Elischer wrote:

> > One thing that shocked me is that a TCP connection in FreeBSD (at least on
> > my machines)
> > doesn't begin with a slow start but rather sends a huge amount of packets t
> o
> > the other end
> > (this huge amount only seems to be limited either by the receiver window or
> > by the local machine's
> > send buffer). It seems that cwnd isn't initialised.
> 
> It is my understanding that it does this only if the destination is considere
> d
> 'local'
> (i.e in the same subnet.)

This is my recollection too, but I can't off-hand recall the reference 
for this (other than looking in the source code).

I'm betting that these sysctl variables let one tweak this behavior:

net.inet.tcp.slowstart_flightsize: 1
net.inet.tcp.local_slowstart_flightsize: 65535

Bruce.



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