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Domain name

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A domain name is the unique name of a computer on the Internet that distinguishes it from the other systems on the network.

Every website, email account, etc, on the Internet is hosted on at least one computer (server). Each server has a unique IP address which is nothing but a set of numbers, such as "207.142.131.235". To access a particular internet service, one can specify its IP address in an appropriate application, such as an FTP client; however because it is difficult to remember numbers, an IP address can be associated with a fully qualified host name (a domain name), such as "www.wikipedia.org". Domain names also provide a persistent address for some service when it is necessary to move to a different server, which would have a different IP address.

Each set of letters and numbers between the dots is called a label in parlance of the domain name service (DNS). There are some rules about the size and make up of labels. Each must start with a letter or number, and then may be made up of letters, numbers, and hyphens, to a maximum of 63 characters. These are the rules imposed by the way names are looked up ("resolved") by DNS. Some top level domains (see below) impose more rules, like a minimum length, on some labels. Fully qualified names are sometimes written with a final dot.

Translating numeric addresses to alphabetical ones, domain names allow Internet users to localize and visit websites. Additionally since more than one IP address can be assigned to a domain name, and more than one domain name assigned to an IP address, one server can have multiple roles, and one role can be spread among multiple servers.

Examples

The following examples illustrates the difference between a URL and a Domain name:

URL: http://www.wikipedia.org/
Server name: www.wikipedia.org
Domain name: wikipedia.org
Subdomain: www
Second level domain: wikipedia
Top level domain: org

As a general rule, the IP address and the server name are interchangeable. For most internet services, the server will not have any way to know which was used. The big exception to this is for web addresses. The explosion of interest in the web means that there are far more websites than servers. To accommodate this the hypertext transfer protocol (HTTP) specifies that the client tells the server which name is being used. This way one server, with one IP address, can provide different sites for different domain names.

As of this writing, the server at 207.142.131.202 handles all of the following sites (and probably many more):

www.wikipedia.org
en.wikipedia.org
fr.wikipedia.org
es.wikipedia.org

That server is one of four handling the www.wikipedia.org traffic.

To be continued...

Official assignment

ICANN (Internet Corporation for Assigned Names and Numbers) controls the domain name root to regulate the Internet (accrediting domain names registries) and manage the Domain Name System (DNS). For ccTLDs, each country has its own domain registries. ICANN has only a consultation role to these domain registries but is in no position to regulate the terms and conditions and the operations of how/who a domain name is allocated in each of these country level domain registries. Since gTLDs is govern directly under ICANN, all terms and conditions are defined by ICANN with the coorperations of the generic top-level domains (gTLD) registries.

Domain names which are theoritically leased can be considered in the same way that real estate due to a significant impact on online brand building and advertising, search engine optimization etc.

Top Level Domains

Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of general names, or a ISO-3166 two character country code.

Examples of (gTLD) extensions are:

.com, .net, .org, .biz, .info, .museum...

Examples of country code top-level domain (ccTLD) extensions are:

.us, .uk, .fr, .es, .de, .it...

  • Icann.org, Internet Corporation for Assigned Names and Numbers.
  • UDRP, Uniform Domain-Name Dispute-Resolution Policy.
  • Internic.net, public information regarding Internet domain name registration services.
  • IcannWatch.org, a watchdog group that publishes ICANN-related news and articles.
  • Name Matters Domain Name Community
  • DNS Conditional Forwarding - Conditional forwarding can be used to speed up the DNS name resolution process by directing queries for specific domains to specific name servers.
  • Public Interest Registry Registry services for the .org extension
  • about.museum Information about the .museum top-level domain
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