Date: Sat, 04 Jan 2014 11:20:13 -0800 From: Peter Wemm <peter@wemm.org> To: freebsd-net@freebsd.org Cc: Gavin Atkinson <gavin@FreeBSD.org>, andre@freebsd.org, Peter Wemm <peter@freebsd.org> Subject: Re: Long-haul problems - connections stuck in slow start Message-ID: <52C85EED.801@wemm.org> In-Reply-To: <52C85537.7080307@wemm.org> References: <52C85537.7080307@wemm.org>
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[-- Attachment #1 --] On 1/4/14, 10:38 AM, Peter Wemm wrote: > We're seeing some unfortunate misbehavior with tcp over an intercontinental > link. I forgot to mention, the socket buffers have been generously tuned for these endpoints. They don't seem to be being used while the sender is in some sort of limited transmit mode. When reading the tcpdumps, keep in mind the window scaling factor is 11 and that's wasn't captured in the session. You'll have to manually compensate when reading the mid-session dumps. XXX footnote: It seems turning SACK off makes a huge difference for this connection. The server must have been running with sack disabled when it was working and hadn't been saved in sysctl.conf. Turning sack off on the server again has raised the throughput from 8K/sec to 32MB/sec. That's a nice 400x speedup. I'm investigating. -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI6FJV UTF-8: for when a ' just won\342\200\231t do. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlLIXu0ACgkQFRKuUnJ3cX8ORgCdGqZX/IMlh5I8TScjlHeXhcNb cFMAmgKr7VehEc8qO78XQngQJLycdyXT =yPlr -----END PGP SIGNATURE-----
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