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
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