I. Background of Remote Desktop for Windows
Remote Desktop Protocol (RDP) is a proprietary protocol developed by Microsoft that enables users to interface with another computer through a graphical interface. RDP is based on, and is an extension of, the T-120 family of protocol standards, which is a multichannel capable protocol allowing for separate virtual channels for carrying presentation data, serial device communication, licensing information, highly encrypted data (keyboard, mouse activity), etc.
RDP supports multipoint (multiparty sessions) data delivery, allowing data from an application to be delivered in "real-time" to multiple parties without having to send the same data to each session individually (for example, Virtual Whiteboards). Thus, RDP is designed to support different types of network topologies and multiple LAN protocols.
RDP listens on TCP port 3389 by default, and uses RSA Security's RC4 cipher, a stream cipher designed to efficiently encrypt small amounts of data to secure communications over networks. Beginning with Windows 2000, administrators can choose to encrypt data by using a 56 or 128-bit key.
Updated versions of RDP include new functions and enhancements:
- Windows 2000: Terminal Services includes enhanced RDP 5.0. The Terminal Services Advanced Client (TSAC) also supports the RDP 5.0 feature set. While continuing to provide excellent performance over the LAN, RDP 5.0 also provides enhanced performance over low-speed connections.
- Windows XP: Uses RDP 5.1 for Remote Desktop Connection and for Remote Assistant. Windows XP also includes Remote Desktop Web Connection, which is an updated version of TSAC (an RDP client based on a Microsoft ActiveX control). Remote Desktop Web Connection supports RDP 5.1 and RDP 5.0. Starting from RDP 5.1, new features are supported including Smart Card authentication, keyboard hooking (directing special Windows key combinations), and sound, drive, port, and network printer redirection. RDP 5.1 also has improved performance over low-speed dial-up connections through reduced bandwidth.
- Windows Server 2003: Uses RDP 5.2 for Remote Desktop Connection and for Remote Assistant. Remote Desktop Web Connection supports RDP 5.2 and is backward compatible with RDP 5.1 and 5.0. Major enhancement of RDP 5.2 includes the support of secured remote desktop connections using TLS/SSL based authentication.