by Greg Shields

Distilling to bare minimums, Terminal Services can be broken down into two halves. First, is the “sessioning” half, which is the ability of Microsoft Windows to simultaneously host multiple user sessions on the same server. Each user session is administratively separate from others, with its own identified processes, threads, and user profiles. Any application installed to a server can be used by a session, with the processes needed by that application invoked as necessary by the session. You can see limited evidence of this in the Remote Desktop functionality used to administratively connect to servers and workstations. It is, however, important to note that there are a few specific differences between how sessioning works in Terminal Services as opposed to what is done with Remote Desktop. For example, with Terminal Services, there is a layer of abstraction created between a user’s remote session and the actual resources on the server itself. That layer of abstraction redirects file and registry pointers to prevent conflict as numerous users leverage the same server. With Remote Desktop, no such redirection occurs, which is one of the reasons Remote Desktop connections are limited in number.

Second is the “transport” half, which is the ability to transport screen updates and keyboard/mouse commands between server and client over a network. With Terminal Services, this functionality is accomplished using RDP. RDP works well over relatively slow and/or latent network connections because it transfers a minimum of data between server and client. For example, from the server, client updates to a particular area of the screen are only transferred when a change occurs in that space. Data transferred from client to server is effectively zero unless attached peripherals such as mouse or keyboard are moved or clicked.

Although there are a lot of other pieces that work together to make up this service, most can be classified as either management functionality or mechanisms that make it easier or more secure for users to connect to sessions. The end result is the ability for multiple users to connect to the same server for the purposes of sharing the use of applications installed to the server.

The big benefit to the business organization is in reducing the overall count of installed applications across the environment. Fewer installed applications means fewer points of administration and fewer places to patch. The benefit to employees is the always-available nature of Terminal Services-hosted applications. If a user has access to the proper client and the right network connectivity, they can access their needed applications from anywhere.

About the Author

Greg Shields is an independent author, speaker, and IT consultant, as well as a Partner and Principal Technologist with Concentrated Technology. With 15 years in information technology, Greg has developed extensive experience in systems administration, engineering, and architecture specializing in Microsoft OS, remote application, systems management, and virtualization technologies. He is a Contributing Editor and columnist for TechNet Magazine and Redmond Magazine, and serves as the Series Editor for Realtime Publishers, the world’s leading provider of high-quality content for the IT market. Greg is a highly sought-after and top-ranked speaker for both live and recorded events, and is seen regularly at conferences like TechMentor Events, Microsoft Tech Ed, VMworld, and more. He is a multiple recipient of Microsoft “Most Valuable Professional” award.