Re: ssh, HPN extension and TCP auto-tuning

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	Hello.  I spent quite a bit of time looking at this under NetBSD-5 and
discovered that the default ssh settings, along with the default tcp
network settings precluded the adaptive network performance from working.
As a result, I've added the following lines to the ssh configs as well as
the sysctl.conf files on the NetBSD-5 hosts we manage.  As faras I've been
able to tell, we've been able to realize good performance gains as a result
of these changes.  Unless there have been a lot of regressions, I have no
reason to believe that these settings won't yield similar performance
improvements under NetBSD-7 and NetBSD-8.


Here are the fixes I came up with.

</etc/sysctl.conf>
# Improves TCP performance significantly with ssh.
net.inet.tcp.recvbuf_auto=1
net.inet.tcp.sendbuf_auto=1
net.inet.tcp.sendbuf_max=16777216
net.inet.tcp.recvbuf_max=16777216

<ssh.conf changes>


# Put the following lines in both /etc/ssh/ssh_config
# and /etc/ssh/sshd_config

#Enable High Performance Networking options (BB 12/27/2010)

#Turn on HPN features
HPNDisabled no

#Allow 5MB of ssh window buffer
HPNBufferSize 5000 

#Enable dynamic window sizing of SSH buffers 
#You must have tcp autotuning turned on in the kernel for this to work
TcpRcvBufPoll yes