Port forwarding allows any TCP-based application or service to take advantage of all the benefits of a secure tunnel between two hosts. After you have set up a secure tunnel, the participating applications operate transparently. For example, when you forward a regular TELNET connection through SSH, all information, including your user name, password, and actual data, are automatically encrypted and checked for integrity.

X11 port forwarding encrypts the X protocol (for X Window Systems). Using SSH, you can invoke X Window programs on a remote machine and have them appear on your local display. In this case, all X-protocol data is secured.

This chapter describes the following: