It's simply not practical to have a keyboard, video display and mouse (KVM) for every server. Part of the problem is that a data center would become swamped with user interface devices. But servers are also independent systems, so once a server is configured and operating properly, it's not necessary to have user interface devices attached until an administrator needs to check or change something. Admins have long relied on an electro-mechanical KVM switch box to swap a single keyboard/video/mouse seamlessly among servers. The idea is to cable the keyboard, video and mouse port of each server to the KVM switch and then cable the switch to a single keyboard, video display, and mouse at a console. Larger data centers may include a KVM switch and console at every rack.
But today's ubiquitous Ethernet environments provide a network alternative to traditional electro-mechanical KVM switches. KVM-over-LAN (or KVM-over-IP) technology allows a server's keyboard, video and mouse data to be compressed and encapsulated into Ethernet packets and passed to a single console. This is accomplished by connecting a server's user interface ports to a specialized KVM switch, which is then wired to the network. Several vendors offer network-based KVM switches,including Avocent, Minicom, Raritan Computer Inc. and Rose Electronics.
With this approach, an administrator can control any number of servers (overcoming the limitation of devices connected to a traditional KVM switch "box") from any network location. An administrator can use KVM-over-IP, for example to access all his local data center servers from the comfort of his office cubicle, and then manage remote servers in another state or region with equal ease.
The truth is that virtually all server management tools enable some form of remote access and control. The difference is that KVM-over-IP is agnostic of server vendor or underlying operating system, so the technology can be particularly attractive to organizations developing heterogeneous data centers.