Saturday, September 17, 2011

Faster SSH with Multiplexing

OpenSSH allows you to speed up multiple SSH connections to the same server using "multiplexing". The first connection acts as the "master" and any other connections reuse the master instance's network connection rather than initiating new ones.

In order to set this up add the following to your ~/.ssh/config file:

Host *
ControlMaster auto
ControlPath /tmp/%r@%h:%p
ControlMaster auto will use a master if one exists, or start a master otherwise. ControlPath is the path to the control socket used for connection sharing. %r, %h and %p are replaced with your username, host to which you are connecting and the port respectively.

In addition, you may want to add Ciphers arcfour in order to use the arcfour cipher which is faster than the default (aes128-cbc). The transfer rate of arcfour is about 90 MB/s, aes128-cbc is about 75 MB/s and the slowest is 3des-cbc, at 19 MB/s.

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