Date: Tue, 16 Aug 2011 17:36:19 -0400 From: Chip Marshall <chip@2bithacker.net> To: Kevin Oberman <kob6558@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: Odd TCP RFC1323 Behavior Message-ID: <20110816213619.GD18638@2bithacker.net> In-Reply-To: <CAN6yY1s9nG5Q9AeVQiXm8mRgr3FELTPDTq9CVkWjpTxHx1Q-Eg@mail.gmail.com> References: <20110812214309.GI72508@2bithacker.net> <CAN6yY1s9nG5Q9AeVQiXm8mRgr3FELTPDTq9CVkWjpTxHx1Q-Eg@mail.gmail.com>
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--LTeJQqWS0MN7I/qa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 12-Aug-2011, Kevin Oberman <kob6558@gmail.com> sent: > Try installing security/openssh-portable from ports and enable > the HPN patches. >=20 > As it stands today, openssh locks the window size to a tiny > value. This causes performance over wide area links to be > simply terrible. >=20 > Take a look at http://fasterdata.es.net/fasterdata/say-no-to- > scp/ for more information on the issue. As you will see there, > window scaling is the least of the performance issues with > openssh. I've installed OpenSSH with the HPN patch on both the sender and receiver and repeated my tests, but it doesn't appear to be any better. As I understand it, if either side of the TCP connection declines to use RFC1323, the TCP receive window can't get any larger than 65K, which appears to be the limiting factor here. Before HPN: chip@test-client:~> scp test-server:~/testfile ./ testfile 100% 10MB 269.5KB/s 00:38 = =20 After HPN: chip@test-client:~> /usr/local/bin/scp test-server:~/testfile ./ testfile 100% 10MB 269.5KB/s 448.0KB/s 00:38 = =20 If I go in the other direction, I get better throughput. In this case, both sides are using RFC1323 window scaling: Before HPN: chip@test-server:~$ scp testfile test-client:~/ testfile 100% 10MB 409.6KB/s 800.0KB/s 00:25 = =20 After HPN: chip@test-server:~$ scp testfile test-client:~/ testfile 100% 10MB 445.2KB/s 576.0KB/s 00:23 = =20 --=20 Chip Marshall <chip@2bithacker.net> http://weblog.2bithacker.net/ KB1QYW PGP key ID 43C4819E v4sw5PUhw4/5ln5pr5FOPck4ma4u6FLOw5Xm5l5Ui2e4t4/5ARWb7HKOen6a2Xs5IMr2g6CM --LTeJQqWS0MN7I/qa Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (Darwin) iEYEARECAAYFAk5K4tIACgkQnTUxIUPEgZ7WMgCZASLdGop8K3CA9rZv0dJugPLn nN4An1qv5TWjpm+BAUzmpE7EQFyDpYqb =+Rg/ -----END PGP SIGNATURE----- --LTeJQqWS0MN7I/qa--
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