Server Alive interval simply sends a null packet to the server at a set time to keep the connection alive, you should just be able to add some thing like into your config file: ~/.ssh/config
Host *
ServerAliveInterval 60
The second line must be indented with at least one space.
* will match any host; if you wanted you could restrict this to particular destinations like *somedomain.com.
Check out http://kehlet.cx/articles/129.html