Remote Desktop Protocol Explained

Remote Desktop Protocol (RDP) is a multi-channel protocol that allows a user to connect to a computer running Microsoft Terminal Services. Clients exist for most versions of Windows (including handheld versions), and other operating systems such as Linux, FreeBSD, Solaris and Mac OS X. Also PalmOS has a client. The server listens by default on TCP port 3389.^[1] Microsoft refers to the official RDP client software as either Remote Desktop Connection (RDC) or Terminal Services Client (TSC).

Features

• 32-bit color support. 8-, 15-, 16-, and 24-bit color are also supported.
• 128-bit encryption, using the RC4 encryption algorithm (this is the default security; older clients may use encryption of lesser strength). But because of the man-in-the-middle vulnerability in pre-version 6.0 implementations, in many circumstances the traffic can be decrypted along the way.^[2]
• Transport Layer Security support.
• Audio allows users to run an audio program on the remote desktop and have the sound redirected to their local computer.
• File System Redirection allows users to use their local files on a remote desktop within the terminal session.
• Printer Redirection allows users to use their local printer within the terminal session as they would with a locally or network shared printer.
• Port Redirection allows applications running within the terminal session to access local serial and parallel ports directly.
• The clipboard can be shared between the remote computer and the local computer.

The following features were introduced with the release of RDP 6.0 in 2006:

• Remote Programs: Application publishing with client-side file type associations.
• Seamless Windows: Remote applications can run on a client machine that is served by a Remote Desktop connection.
• Terminal Server Gateway: Enables the ability to use a front-end IIS server to accept connections (over port 443) for back-end Terminal Services servers via an https connection, similar to how RPC over https allows Outlook clients to connect to a back-end Exchange 2003 server. Requires Windows Server 2008
• Support for remoting the Aero Glass Theme (or Composed Desktop), including ClearType font smoothing technology.
• Support for remoting of Windows Presentation Foundation applications: Compatible clients that have .NET Framework 3.0 support will be able to display full Windows Presentation Foundation effects on a local machine.
• Rewrite of device redirection to be more general-purpose, allowing a greater variety of devices to be accessed.
• All of Terminal Services will be fully configurable and scriptable via Windows Management Instrumentation.
• Improved bandwidth tuning for RDP clients.
• Support for Transport Layer Security (TLS) 1.0 on both server and client ends (set as default).
• Multiple monitor support. Spread session across two monitors.

Implementations

The RDP service is supported as an official feature on Windows Server 2008, Windows Server 2003, Windows Home Server, Windows XP Professional, Windows XP Media Center and Tablet PC Editions, Windows Fundamentals for Legacy PCs, and in Windows Vista Ultimate, Enterprise and Business editions. By default, all Windows XP and Vista editions include the Remote Desktop Connection (RDC) client application pre-installed, with RDC client version determined by the version of Windows release. It is available for free download for Windows Vista, Windows XP, Windows 2000, Windows 9x, Windows NT 4.0, Mac OS X, and most Linux distributions.

xrdp is an open source implementation of the RDP server available for Unix-like operating systems.^[3]

Version history

Based on the ITU T.share protocol (also known as T.128), the first version of RDP (called version 4.0) was introduced with Terminal Services in Windows NT 4.0 Server, Terminal Server Edition. Version 5.0, introduced with Windows 2000 Server, added support for a number of features, including printing to local printers, and aimed to improve network bandwidth usage. Version 5.1, introduced with Windows XP Professional, included support for 24-bit color and sound. Version 5.2, introduced with Windows Server 2003, included support for console mode connections, a session directory, and local resource mapping. Version 6.0 was introduced with Windows Vista and incorporated support for remoting individual programs, Windows Presentation Foundation applications, multi-monitor and large desktop support, and support for TLS 1.0 connections. ^[4] Version 6.1 was released in February 2007 and is included with Windows Server 2008, as well as with Windows Vista Service Pack 1 and Windows XP Service Pack 3. In addition to changes related to how a remote administrator connects to the "console",^[5] this version incorporates new functionality introduced in Windows Server 2008, such as a new Terminal Services Easy Print driver, a new client-side printer redirection system that makes the client's full print capabilities available to applications running on the server, without having to install print drivers on the server.^[6]

See also

• Comparison of remote desktop software
• Independent Computing Architecture
• rdesktop - free open source client for Unix platforms
• tsclient - free open source GUI frontend to rdesktop (Ubuntu, Gnome)

External links

• Technical Overview of Terminal Services - a more detailed feature list.
• Remote Desktop Protocol - from Microsoft's Developer Network
• Understanding the Remote Desktop Protocol - from support.microsoft.com

Notes and References

1. Microsoft KB article 306759, revision 2.2.
3. http://xrdp.sourceforge.net/ xrdp homepage
4. Microsoft KB article 925876, revision 7.0.
5. Web site: Changes to Remote Administration in Windows Server 2008. December 17 2007. 2008-02-10. Terminal Services Team Blog. Microsoft.
6. Web site: Terminal Services Printing. January 10 2008. 2008-02-10. TechNet - Windows Server 2008 Technical Library. Microsoft.