Date: Tue, 25 Aug 2015 15:47:28 -0700 From: Chris Stankevitz <chris@stankevitz.com> To: freebsd-net@freebsd.org Subject: ssh over WAN: TCP window too small Message-ID: <55DCF080.7080208@stankevitz.com>
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Hi, # 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? Thank you, Chris
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