RDP (Remote Desktop Protocol) is a protocol for connecting a user to a remote desktop via a terminal server.

The technology appeared in the 90s and is still in use. The development is completely proprietary, available only on Windows operating systems. However, you can also connect via other operating systems using third-party applications.

Connection mode

RDP is used in 3 modes:

  1. Protocol connection to the server OS for configuration or management. This is due to the fact that Windows Server supports two remote connections and one local login in parallel, and workstations are only one option.
  2. RDP serves as a transport for connecting to the terminal server. This mode is available only for server operating systems. The number of connections is unlimited, but you will need to install a license server.
  3. Connecting to a workstation. The user, using RDP, connects to his office or home computer for further work.

If you need to establish a connection between the Windows and Linux OS family, then for the second one, applications that support working with the RDP protocol are used, for example, Remmina, Rdesktop, Vinagre, etc.

The principle of operation

The principle of operation of RDP is based on the TCP protocol. The client-server connection takes place at the transport layer. After initialization, the user authenticates. In case of successful confirmation, the server transfers control to the client.

The RDP protocol internally supports virtual channels through which additional operating system functions are transmitted to the user, for example, you can print a document, play a video or copy a file to the clipboard.


The technology provides connection security in two ways. The first uses an internal subsystem (Standard RDP Security). An RSA key pair and a public key certificate are generated on the remote machine, which is signed by one of them.

During the connection, the client receives a signed certificate and a public key, which is used to select the data encryption technology. The length of the encryption key depends on the version of the operating system, in older versions of Windows Server 2008 the value was 168 bits. Authorization takes place after confirming the certificate and entering the password.

The second method suggests using external security tools (Enhanced RDP Security). As an example, let’s talk about the TLS protocol. During connection initialization, it encrypts the connection and checks the user’s login permission. This approach reduces the load on the terminal server with a large number of simultaneous connections. The principle of operation is similar to the first option. As a rule, large companies use the second option, and small ones use the first one.

The RDP protocol is used for remote connection only in the Windows environment. The connection is completely secure, as it uses encryption and user authentication procedure. For other operating systems, there is special software that supports working with RDP.

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