Nagle in OpenSSH

OpenSSH by default enables NODELAY flags on the TCP socket, so each key stroke that you make is send as a separate packet. In some situation it is not a very good idea and you would like to have Nagle algorithm enabled.

Nothing ground braking, you can "enable" it by using a simple script (version written in C which is using TCP_CORK socket option) and ProxyCommand option.

The usage, run ssh command like that (or change your ~/.ssh/config):

ssh -o "proxycommand nagle.py %h %p" user@host

and read man ssh :)

you can modify the Nagle parameters by changing those variables:

  n_l    = 5    # how many timeout do we wait for

  n_tout = 0.1  # actual max wait is n_tout*n_l

  n_size = 1024 # minimum size of the packet

maybe this will be useful for somebody :)

PS. Just to add, there is also a SOCKS client that has Nagle support.

PS2. Interesting socket options in Linux and FreeBSD TCP_CORK and TCP_NOPUSH

PS3. Of course you could also just use socat like this, it also works nicely:

ProxyCommand /usr/bin/socat - TCP:%h:%p,cork

Similar post: SSH over SSL