Second-level (or lower-level, depending on the established parent hierarchy) domain names are often created based on the name of a company (e.g., "bbc".co.uk), product or service (e.g. "hotmail".com). Below these levels, the next domain name component has been used to designate a particular host server. Therefore, "ftp.example.com" might be an FTP server, "www.example.com" would be a World Wide Web server, and "mail.example.com" could be an email server, each intended to perform only the implied function. Modern technology allows multiple physical servers with either different (cf. load balancing) or even identical addresses (cf. anycast) to serve a single hostname or domain name, or multiple domain names to be served by a single computer. The latter is very popular in Web hosting service centers, where service providers host the websites of many organizations on just a few servers.