Terminal Server is 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 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:
- Lower hardware costs: “Thin clients” (special devices or stripped-down PCs) can be used instead of full-featured desktop PCs. For example, Windows NT Server, Terminal Server Edition, can present a 32-bit Windows user environment on older PCs that lack the hardware requirements for running a local copy of the latest versions of Microsoft Windows operating systems.
- Lower management costs: Operating systems and applications are installed and run only on the back-end terminal servers, which simplifies deployment and troubleshooting and makes administration more centralized. Windows NT Server, Terminal Server Edition, and Windows 2000 Server, for example, support running applications such as Microsoft Office from central servers instead of installing them on every desktop client in the enterprise.
- Multiplatform support: Allows the same applications and desktop environments to be presented on a variety of client platforms, including Windows-based PCs, Macintosh computers, UNIX workstations, and other devices.
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.