Date: Thu, 27 Aug 2015 09:28:09 +1000 From: Jan Mikkelsen <janm@transactionware.com> To: Chris Stankevitz <chris@stankevitz.com> Cc: freebsd-net@freebsd.org Subject: Re: ssh over WAN: TCP window too small Message-ID: <735A62B2-EFBC-4A4A-9782-F809EC1069E3@transactionware.com> In-Reply-To: <55DCF080.7080208@stankevitz.com> References: <55DCF080.7080208@stankevitz.com>
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Hi, > On 26 Aug 2015, at 08:47, Chris Stankevitz <chris@stankevitz.com> = wrote: >=20 > Hi, >=20 > # cat /dev/urandom | ssh root@host 'cat > /dev/null' >=20 > 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). Given that you are TCP window limited, do you have something in the = middle preventing the windows size negotiation from working? A stateful = firewall somewhere, perhaps? > Both sides of the connection: FreeBSD 10.1 w/default sshd options = (except I permit root login). In particular, HPN is not disabled. >=20 > Can anyone explain my abysmally small TCP window? >=20 > 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? Regards, Jan.=
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