Date: Tue, 16 Dec 2003 15:42:59 -0800 From: Eli Dart <dart@nersc.gov> To: Alex (ander Sendzimir) <xela@battleface.com> Cc: freebsd-net@freebsd.org Subject: Re: suffering from poor network performance... Message-ID: <20031216234259.5C368F8EB@gemini.nersc.gov> In-Reply-To: Message from Alex (ander Sendzimir) <xela@battleface.com> <5099DCD8-301B-11D8-A624-000A95775140@battleface.com>
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--==_Exmh_-412174288P Content-Type: text/plain; charset=us-ascii In reply to Alex (ander Sendzimir) <xela@battleface.com> : > First, I know very little about networking, especially performance > turning. I would really like to learn more but don't know where/how to > start effectively. Take a look at the tools ttcp, netperf and iperf. They build straight out of ports. Also, there are several good network tuning sites out there -- this one has most of them listed (take a look at the links page): http://www-didc.lbl.gov/TCP-tuning/TCP-tuning.html Note that most of the techniques covered here are for high-bandwidth, high-latency links (long fat pipes). Bumping up your tcp buffers a bit might help a bit, but for the most part the machines you have should saturate a 100Mbps link with no trouble at all. If you see a bit less than that, realize that you're connected to a hub, and so you're doing collision detection. Fast Ethernet performance falls off pretty quickly in the face of competing traffic on a hub. Note also that if you just crank up your tcp buffers to something large without thinking about what you're doing, you can actually decrease performance. As someone else pointed out, using ping as a measure of network performance often doesn't give reliable results, since most operating systems (including FreeBSD) rate limit ICMP in various ways to protect against DoS attacks. Hope this helps, --eli > > Thanks for the help. > Alex --==_Exmh_-412174288P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.3 (FreeBSD) Comment: Exmh version 2.5 07/13/2001 iD8DBQE/35iDLTFEeF+CsrMRAor9AJ95tG8DUY9tmPkM86nDzEoCdThkdACdEvut xsAjAwDu+XgAGTHomTgAeLA= =GVo1 -----END PGP SIGNATURE----- --==_Exmh_-412174288P--
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