11. Getting the Best Performance Out of SSH

11.1. Cipher Speed

SSH and SCP accept command-line options to specify the cipher preferred in the connection. The default cipher depends on the SSH implementation, but is unlikely to be Blowfish --- this is likely to be faster (and a little less secure) than the default. To enable Blowfish for all your connections for OpenSSH your ~/.ssh/config file should read like this:

  Host *
    Cipher blowfish

  Host *
    Ciphers blowfish

11.2. Compression

SSH also facilitates the compression of network traffic. Whilst this takes up a few more CPU-cycles, it makes network connections over slow links like modem lines much faster:

  Host *
    Compression yes
    Cipher blowfish