Socio

Terminal server
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Not to be confused with Terminal Services or Remote Access Service.
| It has been suggested that Console server be merged into this article or section. (Discuss) Proposed since May 2011. |

| This article does not cite any references or sources. Please help improve this article by adding citations toreliable sources. Unsourced material may be challenged and removed. (December 2009) |
A terminal server (also referred to as a serial server or network access server) enables organizations to connect devices with an RS-232, RS-422 or RS-485 serial interface to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality,such as data encryption and user authentication. The primary application scenario is to enable serial devices to access network server applications, or vice versa, where security of the data on the LAN is not generally an issue. There are also many terminal servers on the market that have highly advanced security functionality to ensure that only qualified personnel can access various servers andthat any data that is transmitted across the LAN, or over the Internet, is encrypted. Usually companies which need a terminal server with these advanced functions want to remotely control, monitor, diagnose and troubleshoot equipment over a telecommunications network.
History
Historically, a terminal server was a device that attached to serial RS-232 devices, such as "green screen" text terminalsor serial printers, and transported traffic via TCP/IP, Telnet, SSH or other vendor-specific network protocols (e.g. LAT) via an Ethernet connection.
Digital Equipment Corporation's DECserver 100 (1985), 200 (1986) and 300 (1991) are early examples of this technology. (An earlier version of this product, known as the DECSA Terminal Server was actually a test-bed or proof-of-concept for using theproprietary LAT protocol in commercial production networks.) With the introduction of inexpensive flash memory components, Digital's later DECserver 700 (1991) and 900 (1995) no longer shared with their earlier units the need to download their software from a "load host" (usually a Digital VAX or Alpha) using Digital's proprietary Maintenance Operations Protocol (MOP). In fact, these laterterminal server products also included much larger flash memory and full support for the Telnet part of the TCP/IP protocol suite.
Many other companies entered the terminal-server market with devices pre-loaded with software fully compatible with LAT and Telnet. Some manufacturers stated specifically they had emulated Digital's terminal-server management command-set. Besides retaining the ability ofthe older terminal-servers to obtain their run-time code from a load host, most could bootstrap from on-board flash memory or from a floppy drive in the terminal server. Some terminal servers could act as load hosts for each other; one would hold the code on a PCMCIA flash card and serve it to another...
Modern usage
A "terminal server" is used many ways but from a basic sense if a user has aserial device and they need to move data over the LAN, this is the product they need.
* Raw TCP socket connection: A raw TCP socket connection which can be initiated from the terminal server or from the remote host/server. This can be point-to-point or shared, where serial devices (like card readers, scanners, bar code readers, weight scales, etc.) can be shared amongst multiple devices. TCPsessions can be initiated from the TCP server application or from the terminal server.
* Raw UDP socket connection: For use with UDP based applications, terminal servers can convert serial equipment data for transport across UDP packets on a point-to-point basis or shared across multiple devices.
* Console management - reverse Telnet, reverse SSH: In console management terminology, users can...