<Ul> <Li> The right-most label conveys the top - level domain ; for example , the domain name www.example.com belongs to the top - level domain com . </Li> <Li> The hierarchy of domains descends from the right to the left label in the name ; each label to the left specifies a subdivision , or subdomain of the domain to the right . For example : the label example specifies a node example.com as a subdomain of the com domain , and www is a label to create www.example.com , a subdomain of example.com . Each label may contain from 1 to 63 octets . The empty label is reserved for the root node and when fully qualified is expressed as the empty label terminated by a dot . The full domain name may not exceed a total length of 253 ASCII characters in its textual representation . Thus , when using a single character per label , the limit is 127 levels : 127 characters plus 126 dots have a total length of 253 . In practice , some domain registries may have shorter limits . </Li> <Li> A hostname is a domain name that has at least one associated IP address . For example , the domain names www.example.com and example.com are also hostnames , whereas the com domain is not . However , other top - level domains , particularly country code top - level domains , may indeed have an IP address , and if so , they are also hostnames . </Li> <Li> Hostnames impose restrictions on the characters allowed in the corresponding domain name . A valid hostname is also a valid domain name , but a valid domain name may not necessarily be valid as a hostname . </Li> </Ul>
what are the parts of a domain name called
top - level domain subdomain hostname