From: Kenny Simpson <theonetruekenny@yahoo.com>
Subject: Re: NFS TCP settings
Date: Wed, 21 Dec 2005 08:32:54 -0800 (PST)
Message-ID: <20051221163254.70779.qmail@web34105.mail.mud.yahoo.com>
References: <1135093627.7955.36.camel@lade.trondhjem.org>
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Cc: nfs@lists.sourceforge.net
To: Trond Myklebust <trond.myklebust@fys.uio.no>
In-Reply-To: <1135093627.7955.36.camel@lade.trondhjem.org>
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--- Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> The NFS/RPC code has no direct control over the TCP window size. That
> would be an issue for the networking people.

I have tracked this a bit further, and am reporting back for completeness=
..

The version of OnTap we are using (6.4.1p1) does not seem to support RFC =
1323 (large TCP windows),
but the Linux client does.  The window scaling is communicated in the ini=
tial connection (SYN), so
if ethereal does not catch that, it will incorrectly report the window si=
ze as the unscaled number
- making the Linux client appear to be using a very small window.
The reason it appeared that the small window size was being honored is a =
result of the direct
crossover cable making the BDP (bandwidth-delay product) very small.

As for the server side, because large TCP windows are not supported, the =
best it can do is 64k -
which it does.  Running with GbE and jumbo packets fills the window quite=
 fast obviating the need
for RFC 1323.

Thanks to those who took the time to swing a clue stick in my direction.

-Kenny


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