Dns-domain Name System

Domain Name System From Wikipedia, the free encyclopedia

The Domain Name System (DNS) is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide. For example, www.example.com translates to 208.77.188.166. The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. The Domain Name System also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. The Domain Name System also defines the technical underpinnings of the functionality of this database service. For this purpose it defines the DNS protocol, a detailed specification of the data structures and communication exchanges used in DNS, as part of the Internet Protocol Suite (TCP/IP). [edit]Parts

of a domain name

A domain name usually consists of two or more parts (technically labels), which are conventionally written separated by dots, such as example.com. 

The rightmost label conveys the top-level domain (for example, the

addresswww.example.com has the top-level domain com). 

Each label to the left specifies a subdivision, or subdomain of the domain above it. Note:

“subdomain” expresses relative dependence, not absolute dependence. For example: example.com is a subdomain of the com domain, and www.example.com is a subdomain of the domain example.com. In theory, this subdivision can go down 127 levels. Each label can contain up to 63 octets. The whole domain name may not exceed a total length of 253 octets. [8] In practice, some domain registries may have shorter limits. 

A hostname refers to a domain name that has one or more associated IP addresses

(e.g., the 'www.example.com' and 'example.com' domains are both hostnames, whereas the 'com' domain is not).