Remote Desktop Services - Overview

Overview

Terminal Services was first introduced in Windows NT 4.0 Terminal Server Edition. It was significantly improved for Windows 2000 and Windows Server 2003. All versions of Windows XP, except Home edition, also include a Remote Desktop server. Both the underlying protocol as well as the service were again overhauled for Windows Vista and Windows Server 2008. Windows includes two client applications which utilize terminal services: the first, Remote Assistance is available in all versions of Windows XP and successors and allows one user to assist another user. The second, Remote Desktop, allows a user to log in to a remote system and access the desktop, applications and data on the system as well as control it remotely. However, this is only available in certain Windows editions. These are Windows NT Terminal Server; subsequent Windows server editions, Windows XP Professional, and Windows Vista Business, Enterprise and Ultimate. In the client versions of Windows, Terminal Services supports only one logged in user at a time, whereas in the server operating systems, concurrent remote sessions are allowed.

Microsoft provides the client software Remote Desktop Connection (formerly called Terminal Services Client), available for most 32-bit and 64-bit versions of Windows, including Windows Mobile, and Apple's Mac OS X, that allows a user to connect to a server running Terminal Services. On Windows, both Terminal Services client and Remote Desktop Protocol (RDP) use TCP port 3389 by default, which is editable in the Windows registry. It also includes an ActiveX control to embed the functionality in other applications or even a web page. A Windows CE version of the client software is also available. Server versions of Windows OSs also include the Remote Desktop for Administration client (a special mode of the Remote Desktop Connection client), which allows remote connection to the traditional session 0 console of the server. In Windows Vista and later this session is reserved for services, and users always log onto session >0. The server functionality is provided by the Terminal Server component, which is able to handle Remote Assistance, Remote Desktop as well as the Remote Administration clients. Third-party developers have created client software for other platforms, including the open source rdesktop client for common Unix platforms.

For an enterprise, Terminal Services allows IT departments to install applications on a central server. For example, instead of deploying database or accounting software on all desktops, the applications can simply be installed on a server and remote users can log on and use them via the network. This centralization makes upgrading, troubleshooting, and software management much easier. As long as employees have Remote Desktop software, they will be able to use enterprise software. Terminal Services can also integrate with Windows authentication systems to prevent unauthorized users from accessing the applications or data.

Microsoft has a long-standing agreement with Citrix to facilitate sharing of technologies and patent licensing between Microsoft Terminal Services and Citrix XenApp (formerly Citrix MetaFrame and Citrix Presentation Server). In this arrangement, Citrix has access to key source code for the Windows platform enabling their developers to improve the security and performance of the Terminal Services platform. In late December, 2004 the two companies announced a five-year renewal of this arrangement to cover Windows Vista.