There are three types of remote access services. The first is remote terminal in which the remote computer connects to a corporate system as a dumb terminal. This type of connectivity tends to be more for legacy access to mainframes than for access to desktop systems. The second is remote control in which the remote computer takes over control of the keyboard and the display of a local system as illustrated above. The final type is remote node in which the remote computer appears to act and respond as if it was a local computer connected directly to the corporate network.
Remote node is the prevalent remote access service in use today.
This is where the public switched network gets involved by providing the actual connection between the two points. Depending on the required data rates, reliability, and costs, a choice of either analog or digital connectivity may be available. The next level of security is the ability to authenticate a remote user by identifying them with some level of confidence. Authentication is not the same thing as authorization. To authenticate a user, three basic elements can be required.