virtual server

(World-Wide Web)A configuration of a World-Wide Webserver that appears to clients as an independent serverbut which is actually running on a computer that is shared byany number of other virtual servers. Each virtual server canbe configured as an independent website, with its ownhostname, content, and security settings.

DNS maps the hostnames of all virtual servers on onephysical server to its IP address. The web server softwarethen uses the "Host" header in the HTTP request to determinewhich virtual server the request was for, and then processesthe request using that virtual server's configuration.

Virtual servers allow Internet Service Providers to shareone computer between multiple websites while allowing theowner of each website to use and administer the server asthough they had complete control.

virtual server

(1) See server virtualization. Contrast with virtual host.

(2) A virtual machine environment from Microsoft for Windows servers. See Microsoft Virtual Server.

(3) Multiple servers that appear as one system image to the operating system or to the network administrator. See network virtualization.

(4) One instance of a Web or application server running in a single computer that is hosting multiple Web or application servers. See Web hosting.

(5) Multiple servers that appear as one server for load balancing. For example, all clients use the IP address of the virtual server, which uses address translation to point to a real server based on its load balancing algorithm.

Load Balancing

For load balancing, all clients use the address of the virtual server, which is substituted with the address of one of the real servers. The selection algorithm could be simple round robin or based on the current load of the servers. See round robin.