Naming conventions

In the hierarchical domain name system, names consist of a sequence of case-insensitive subnames separated by periods with no embedded blanks.

The DOMAIN protocol specifies that a local domain name must be fewer than 64 characters and that a host name must be fewer than 32 characters in length. The host name is given first, followed by a period (.), a series of local domain names separated by periods, and finally the root domain. A fully specified domain name for a host, including periods, must be fewer than 255 characters in length and in the following form:

host.subdomain1.[subdomain2 . . . subdomain].rootdomain

Because host names must be unique within a domain, you can use an abbreviated name when sending messages to a host within the same domain. For example, instead of sending a message to smith.eng.lsu.edu, a host in the eng domain could send a message to smith. Additionally, each host can have several aliases that other hosts can use when sending messages.