Generally, a server that provides the back-end support needed for terminals to function. This can be a mainframe system, a UNIX host running X Windows, or a PC-based server running software such as Microsoft Windows NT Server, Terminal Server Edition, or Microsoft Windows 2000 Server. The terminal server generates the desktop environment presented to the user on the terminal and performs all processing of data submitted by the user.
The main advantages of such a system are as follows:
Some vendors produce rack-mountable terminal server devices with 8 or 16 RJ-45 ports that can be used to connect asynchronous terminals to an Ethernet local area network (LAN) running TCP/IP or some other network protocol. Such devices can be used to provide terminals (or PCs running terminal emulation software) with access to network file servers or dial-up access to the Internet. Windows-based management software allows these devices to be remotely managed from a PC for viewing and configuring port information. Built-in support for Password Authentication Protocol (PAP), Challenge Handshake Authentication Protocol (CHAP), and Remote Authentication Dial-In User Service (RADIUS) are often included to control user access. Users can dial in to the device, be authenticated, and select a desired host on the LAN they want to communicate with.
Single-port terminal servers are sometimes used in mainframe environments to allow users connected to different controllers to communicate over the corporate LAN without needing a dedicated point-to-point communication link. In a typical configuration, the controller is connected to a terminal server via an RS-232 serial connection, while the terminal server is linked to the LAN via an Ethernet interface.