Date: Tue, 25 Aug 2015 23:11:06 +0000 From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: Chris Stankevitz <chris@stankevitz.com> Cc: freebsd-net@freebsd.org Subject: Re: ssh over WAN: TCP window too small Message-ID: <27420EDC-5816-4B9E-A834-E4A035B8411C@lists.zabbadoz.net> In-Reply-To: <55DCF080.7080208@stankevitz.com> References: <55DCF080.7080208@stankevitz.com>
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> On 25 Aug 2015, at 22:47 , 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). >=20 > 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? if you have the memory, try these sysctls: kern.ipc.maxsockbuf=3D146800640 net.inet.tcp.recvbuf_max=3D67108864 net.inet.tcp.sendbuf_max=3D67108864=
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