RDP

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

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

Mode of connections

. RDP is used in 3 modes:

1. Connect via the protocol to the server OS for configuration or management. This is because Windows Server supports two remote connections and one local login in parallel, while workstations support only one option.
2. RDP serves as a transport for connecting to a terminal server. This mode is available only for server operating systems. The number of connections is unlimited, but installation of a license server will be required.
4. Workstation connection. The user, using RDP, connects to his office or home computer for further work.

If you need to establish a connection between Windows and Linux, then for the second use applications that support work with the RDP protocol, such as Remmina, Rdesktop, Vinagre and others.

Principle of work

. The principle of RDP is based on the TCP protocol. Client-server connection takes place at the transport layer. After initialization, the user is authenticated. 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 transferred to the user, for example, you can print a document, play a video or copy a file to the clipboard.

Security

. The technology secures connectivity 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 and signed with one of them.

During connection, the client receives the signed certificate and the 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 certificate validation and password entry.

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 permission to log in. This approach reduces the load on the terminal server in case of 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, while small companies 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 RDP.