Domain

Tags

networking

Refers to a collection of machines that share a common name suffix. Domains can live inside other domains, for example www.tldp.org lives in the .tldop.org subdomain of the .org domain.

Domain Name

Is a human-readable identifier for a given host within a domain.

Format

A domain name is a case-insensitive series of labels all joined together by a full-stop. Each label of a domain-name can divide the domain into subdomain, with the right-most domain being the most encompassing. So www.google.com is a sub-domain of google.com which is a sub-domain of the TLD .com.

Sub-domains are often used to designate a particular host server. For example ftp.example.com can point to a file-transfer server below the example.com domain.

Authoritative Name Server

Each domain has a dedicated name server that knows the IP addresses of the other machines in the domain. In many cases such a name server may have backup servers which take over when the main one gets taken down. Such servers may be referred to as secondary DNS.

Note: The authoritative name server doesn't need to list know the IP address of all machines in that domain. It suffices to know the IP address of the name server for each sub-domain that may be referenced. So the name-server for .org may know the IP address of the name-server for .tldp.org but does not need to know the ip-address of all the other machines in .tldp.org.