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Four remote management protocols commonly used in Linux
When talking about remote management, you usually mean remote management servers, not personal computers. The personal computer can be used at any time, and the server is usually placed in the computer room. Users cannot directly access the server hardware and can only use remote management.
Remote management is actually the process of data transmission (information exchange) between computers (servers) through the network. Just as browsers need the HTTP protocol (Hypertext Transfer Protocol) to browse web pages, remote management also requires the support of remote management protocols.
Currently, there are four commonly used remote management protocols:
- RDP (remote desktop protocol) protocol: remote desktop protocol, most Windows systems support this protocol by default, and the remote desktop management in Windows system is based on this protocol.
- RFB (Remote FrameBuffer) protocol: a graphical remote management protocol, the VNC remote management tool is based on this protocol.
- Telnet: Command line interface remote management protocol, almost all operating systems support this protocol by default. The characteristic of this protocol is that it uses plaintext transmission during data transmission, that is, the data is not encrypted.
- SSH (Secure Shell) protocol: Command line interface remote management protocol, almost all operating systems support this protocol by default. Unlike Telnet, this protocol encrypts and compresses data during data transmission, so using this protocol to transmit data is safe and fast.
RDP and RFB
Both the RDP protocol and the RFB protocol allow users to access remote systems through a graphical user interface, but the RFB protocol tends to transfer images, and the RDP protocol tends to transfer instructions:
- The RFB protocol will draw the window in the video memory on the server side, and then transmit the image to the client, and the client only needs to decode and display the obtained image;
- RDP will hand over the drawing work to the client, and the server needs to make appropriate adjustments based on the display capabilities of the client.
Therefore, to complete the same operation, the amount of data transferred using the RFB protocol will be larger than that of RDP, and RDP has stricter requirements on the client than RFB. RFB is suitable for thin clients, while RDP is suitable for low-speed networks.
The "thin client" is relative to the "fat client". For example, when people use QQ, they need to download the client, which is a "fat client"; Then download any other software, which is a "thin client". Simply understood, the thin client refers to reducing the burden on the client as much as possible, and most of the work is done by the server; the thick client is the opposite.
Telnet and SSH
Both the Telnet protocol and the SSH protocol are command-line remote management protocols, have common application areas, and are often used for remote access to servers.
Compared with the Telnet protocol, the SSH protocol encrypts the data when sending data, and the data transmission is more secure, so the SSH protocol replaces the Telnet protocol in almost all application fields.
In some testing and occasions that do not require encryption (such as local area networks), the Telnet protocol is still often used.
Linux remote management software
Based on the above four remote management protocols, the Linux remote management server software can be divided into the following three types:
- Graphical remote management software similar to VNC (based on RFB protocol), such as Xmanager, VNC VIEWER, and TightVNC;
- Command line operation management based on SSH protocol;
- Similar to Webmin's browser-based remote management, this management method only provides a simple management window, and the available management functions are limited;
For the sake of security and stability, most servers choose the command line interface instead of the graphical management interface, so the remote management of Linux servers often uses the command line management method based on the SSH protocol.