Date: Wed, 26 Aug 2015 14:44:56 +0200 From: Mark Martinec <Mark.Martinec+freebsd@ijs.si> To: freebsd-net@freebsd.org Subject: Re: ssh over WAN: TCP window too small Message-ID: <4e28129672e933ab87f1a4cabc9575dc@mailbox.ijs.si> In-Reply-To: <20150826082457.GQ33167@funkthat.com> References: <55DCF080.7080208@stankevitz.com> <20150826010323.GN33167@funkthat.com> <55DD2A98.2010605@stankevitz.com> <20150826082457.GQ33167@funkthat.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Chris Stankevitz wrote: > # cat /dev/urandom | ssh root@host 'cat > /dev/null' > > I use the above ssh command over a high-BDP WAN link (80 ms @ 100 > Mbps). > tcpdump shows I am TCP window limited to 64 KBytes (yielding 5 Mbps). > iperf with default options gets the window opened to 500 KBytes > (yielding 35 Mbps). > > Both sides of the connection: FreeBSD 10.1 w/default sshd options > (except I permit root login). In particular, HPN is not disabled. > > Can anyone explain my abysmally small TCP window? > > Can anyone recommend some tools/tricks to figure out what in FreeBSD > and/or base SSH is limiting the send/recv buffer and/or TCP window? As an alternative to ssh for copying large files across high-BDP WAN links consider sysutils/bbcp, optionally coupled with security/hpenc for encryption. Mark
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4e28129672e933ab87f1a4cabc9575dc>