Wu Bigo

Today I Learned

A collection of concise write-ups about what i learned today and it's build from http://bigo.github.io .These are things that don't really warrant a full blog post


High Performance SSH/SCP

http://mirror.internode.on.net/pub/OpenBSD/OpenSSH/portable/ http://www.psc.edu/index.php/hpn-ssh-patches/hpn-14-kitchen-sink-patches/viewcategory/24 Extract OpenSSH:

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tar -xzvf openssh-6.6p1.tar.gz

Change directory in extracted folder and apply patch:

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cd openssh-6.6p1

zcat /usr/src/openssh-6.6p1-hpnssh14v5.diff.gz patch

Configure OpenSSH:

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./configure –prefix=/usr –sysconfdir=/etc/ssh –with-pam

Remove old config files to prevent any conflicts:

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rm /etc/ssh/ssh_config

rm /etc/ssh/sshd_config

Compile and install:

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make

make install

Now we have the newest version of OpenSSH installed and patched with the improvements from HPN-SSH; however we still need to make some changes to the /etc/ssh/sshd_config to take advantage of them. Near the bottom of your config file you will see a section for HPN related options; I used the following options from other guides I found:

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the following are HPN related configuration options

tcp receive buffer polling. disable in non autotuning kernels

TcpRcvBufPoll yes

allow the use of the none cipher

#NoneEnabled no

disable hpn performance boosts.

#HPNDisabled no

buffer size for hpn to non-hpn connections

HPNBufferSize 8388608

Linux supports both /proc and sysctl (using alternate forms of the variable names - e.g. net.core.rmem_max) for inspecting and adjusting network tuning parameters. The following is a useful shortcut for inspecting all tcp parameters:

sysctl -a fgrep tcp

For additional information on kernel variables, look at the documentation included with your kernel source, typically in some location such as /usr/src/linux-/Documentation/networking/ip-sysctl.txt. There is a very good (but slightly out of date) tutorial on network sysctl's at http://ipsysctl-tutorial.frozentux.net/ipsysctl-tutorial.html.

If you would like to have these changes to be preserved across reboots, you can add the tuning commands to your the file /etc/rc.d/rc.local .

echo 1 > /proc/sys/net/ipv4/tcp_moderate_rcvbuf echo “8388608”> /proc/sys/net/core/wmem_max echo “8388608”> /proc/sys/net/core/rmem_max echo “4096 87380 8388608” > /proc/sys/net/ipv4/tcp_rmem echo “4096 87380 8388608” > /proc/sys/net/ipv4/tcp_wmem

optimization start

increase TCP max buffer size setable using setsockopt()

net.ipv4.tcp_rmem = 4096 87380 8388608

net.ipv4.tcp_wmem = 4096 87380 8388608

increase Linux auto tuning TCP buffer limits

min, default, and max number of bytes to use

set max to at least 4MB, or higher if you use very high BDP paths

net.core.rmem_max = 8388608

net.core.wmem_max = 8388608

net.core.netdev_max_backlog = 5000

net.ipv4.tcp_window_scaling = 1

optimization end

[1] http://www.psc.edu/index.php/hpn-ssh

[2]http://stackoverflow.com/questions/8849240/why-when-i-transfer-a-file-through-sftp-it-takes-longer-than-ftp

[3]http://www.cyberciti.biz/tips/sshd-server-optimization.html