Virtual Network Computing: An Introduction

Virtual Network Computing, or VNC, is a program developed by AT&T to allow users to operate other computers from their own desktop. When it was originally released it was to be used on ‘network computers’ only. That is computers whose main purpose was to connect to a server that would then run the user’s applications as if it was their own machine. Today these machines are known as thin clients, and VNC’s client-server abilities and source code are available for free.

VNC works by allowing client computers (the users’ computers) to connect to the machine running the server part of the software. The server software transmits a compressed image, usually a JPEG, of its current desktop to any authorized clients. Each client can use their mouse and keyboard to control the server. VNC uses the remote framebuffer protocol to transmit the server’s desktop as it changes in the most efficient way possible, conserving bandwidth over the network. It works by updating only a rectangle around the most recent change, keeping things fast but making things like watching videos or playing games in the VNC client window extremely difficult. Also in the interest of keeping things fast, information transferred over VNC is essentially unencrypted in most versions of the software, making it relatively easy for malicious activity to take place.

So how does VNC shape up against Remote Desktop Protocol, the protocol used in Windows default ‘Remote Desktop Connection’ software? It lacks many of the features of RDP, such as strong encryption. Also lacking is the ability to use files on the client machine as if they were on the server. This means that programs on the server cannot access local files, which could be problematic if they are needed. On the other hand VNC is incredibly widely used because it is available on nearly every conceivable platform, so compatibility is not an issue. RDP is not an open source protocol and still unavailable on some platforms, as such there could be problems.