Date: Fri, 28 Aug 2015 12:14:32 -0700 From: Chris Stankevitz <chris@stankevitz.com> To: Kurt Lidl <lidl@pix.net>, freebsd-net@freebsd.org Subject: Re: ssh over WAN: TCP window too small Message-ID: <55E0B318.2090709@stankevitz.com> In-Reply-To: <55DF0D37.5060003@pix.net> References: <55DCF080.7080208@stankevitz.com> <55DF0D37.5060003@pix.net>
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On 8/27/15 6:14 AM, Kurt Lidl wrote: > # tcp options for long-haul speedups > kern.ipc.maxsockbuf=4194304 # (2 * default 2097152) > net.inet.tcp.mssdflt=1448 # (default 576) > net.inet.tcp.sendbuf_max=4194304 # (2 * default 2097152) > net.inet.tcp.recvbuf_max=4194304 # (2 * default 2097152) > > net.inet.tcp.syncache.rexmtlimit=1 # (default 3) > net.inet.tcp.recvspace=262144 # (4 * default 65,536) > net.inet.tcp.sendspace=262144 # (4 * default 65,536) > > net.inet.tcp.sendbuf_inc=65536 # (8 * default 8192) > net.inet.tcp.recvbuf_inc=131072 # (8 * default 16384) Kurt, Thank you. FYI the default for sendspace is 32768 (not 65536). With these parameters my S-BCNT increases from ~60K to ~200K when doing `ssh < /dev/zero`. Amusingly, something somewhere limits bytes-in-flight to 172,888 bytes (I believe the ssh sending client is limiting -- although I'm not sure why). This effectively caps my bandwidth to 20 Mbps. With iperf this limitation does not exist -- nor does the need to tune these values (except for buf_inc which can get the ball rolling faster as you pointed out). Chris
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