VNC - virtual Network Comuting

VNC was produced at the AT&T Research Centre in Cambridge, UK. It's probably most used in a desktop migration environment where users of Open Source desktops will use VNC to view Windows-based systems remotely. In that way a small pool of Windows systems can assist a larger group of Open Source desktop users to use software that they can't find for their preferred operating system but which they still need to use occasionally. It is capable of much more than that, however, since it's really a framework for remote access with multiple implementations. Versions exist for Windows, Macintosh, the various Unixes (including GNU/Linux) and implemented as standalone programs or java which can run within a web browser window. It's like a mini-industry rather than just a 'product'.

The development group's own description is:

VNC stands for Virtual Network Computing. It is, in essence, a remote display system which allows you to view a computing 'desktop' environment not only on the machine where it is running, but from anywhere on the Internet and from a wide variety of machine architectures.

The VNC system allows you to access the same desktop from a wide variety of platforms. Many of us, for example, use a VNC viewer running on a PC on our desks to display our Unix environments which are running on a large server in the machine room downstairs. What makes it different from other systems? For this simple mode of operation, you could achieve a similar effect by installing an X server on your PC. The important factors which distinguish VNC from other remote display systems such as X are as follows:

• No state is stored at the viewer. This means you can leave your desk, go to another machine, whether next door or several hundred miles away, reconnect to your desktop from there and finish the sentence you were typing. Even the cursor will be in the same place. With a PC X server, if your PC crashes or is restarted, all the remote applications will die. With VNC they go on running.
• It is small and simple. The Win32 viewer, for example, is about 150K in size and can be run directly from a floppy. There is no installation needed.
• It is truly platform-independent. A desktop running on a Linux machine may be displayed on a PC. Or a Solaris machine. Or any number of other architectures. The simplicity of the protocol makes it easy to port to new platforms. We have a Java viewer, which will run in any Java-capable browser. We have a Windows NT server, allowing you to view the desktop of a remote NT machine on any of these platforms using exactly the same viewer. (The NT server is not multi-user - see the documentation). And other people have ported VNC to a wide variety of other platforms.
• It is sharable. One desktop can be displayed and used by several viewers at once, allowing CSCW-style applications.
• It is free! You can download it, use it, and redistribute it under the terms of the GNU Public Licence. Both binaries and source code are available from the download page, along with a complete copy of this documentation.

Migrating to VNC

You don't migrate to VNC, you just install and use it.

Reliability

The product has a reputation for stability and reliability

Security

The VNC FAQ suggests that the product applies some security to protect passwords but does not encrypt the data stream, which probably would restrict it to internal network use in most organisations. The FAQ goes on to point out that the data stream could be forwarded using SSH or other network encryption technology. That would be likely to meet the needs of all but the most demanding of users.

Flexibility

Various configurations of VNC are possible and it is certainly not restricted to use only as a remote control tool for PCs. Interested readers should look at the comprehensive documentation on the product website.

Performance

Personal experience has been that VNC access to a PC from a Linux desktop is too slow for full-time use on a regular basis. It is adequate for occasional short periods of use. This is however not necessarily a consensus view from across the industry and other opinions are welcomed.

Standards compliance

It's hard to see any relevant standards. Does anyone know of any?

Licensing and Support

VNC is distributed under the GPL. Although the project that produced VNC has since been disbanded, other projects have since spun off to continue work on it. No information is available about commercial support at the present time, but complaints about lack of support for the product are conspicuous by their absence.

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