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.