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The term domain name has multiple related meanings:
They are sometimes colloquially (and incorrectly) referred to by marketers as "web addresses". This article will primarily discuss registered domain names. See the Domain Name System article for technical discussions about general domain names and the Hostname article for further information about the most common type of domain name. OVERVIEW The most common types of domain names are Hostname s that provide more memorable names to stand in for Numeric IP Addresses . They allow for any service to move to a different location in the topology of the Internet (or an Intranet ), which would then have a different IP address. By allowing the use of unique alphabetical addresses instead of numeric ones, domain names allow Internet users to more easily find and communicate with web sites and other server-based services. The flexibility of the domain name system allows multiple IP addresses to be assigned to a single domain name, or multiple domain names to be assigned to a single IP address. This means that one server may have multiple roles (such as hosting multiple independent Web sites), or that one role can be spread among many servers. One IP address can also be assigned to several servers, as used in Anycast and hijacked IP space. Hostnames are restricted to the ASCII letters "a" through "z" (case-insensitive), the digits "0" through "9", and the hyphen, with some other restrictions. Registrars restrict the domains to valid hostnames, since, otherwise, they would be useless. The Internationalized Domain Name (IDN) system has been developed to bypass the restrictions on character allowances in hostnames, making it easier for users of non-english alphabets to use the Internet. The underscore character is frequently used to ensure that a domain name is not recognized as a hostname, for example with the use of SRV Record s, although some older systems, such as NetBIOS did allow it. Due to confusion and other reasons, domain names with underscores in them are sometimes used where hostnames are required. EXAMPLES The following example illustrates the difference between a URL (Uniform Resource Locator) and a domain name: : URL: : Domain name: : Registered domain name: 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. However, the explosion of interest in the Web means that there are far more Web sites 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. This feature goes under the name '' Virtual Hosting '' and is commonly used by Web Hosts . For example, as referenced in RFC 2606 (Reserved Top Level DNS Names), the server at IP address 192.0.34.166 handles all of the following sites: : example.com : www.example.com : example.net : www.example.net : example.org : www.example.org When a request is made, the data corresponding to the hostname requested is served to the user. TOP-LEVEL DOMAINS Every domain name ends in a Top-level Domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two-character territory code based on ISO-3166 (there are few exceptions and new codes are integrated case by case). Top-level domains are sometimes also called first-level domains. The Generic Top-level Domain (gTLD) extensions are: The Country Code Top-level Domain (ccTLD) extensions are: OTHER-LEVEL DOMAINS In addition to the top-level domains, there are Second-level Domain (SLD) names. These are the names directly to the left of .com, .net, and the other top-level domains. As an example, in the domain ''en.wikipedia.org'', "wikipedia" is the second-level domain. On the next level are third-level domains. These domains are immediately to the left of a second-level domain. In the ''en.wikipedia.org'' example, "en" is a third-level domain. There can be fourth and fifth level domains and so on, with virtually no limitation. An example of a working domain with five levels is ''www.sos.state.oh.us''. Each level is separated by a dot or period symbol between them. Domains of third or higher level are also known as Subdomains , though this term technically applies to a domain of any level, since even a top-level domain is a "subdomain" of the "root" domain (a "zeroth-level" domain that is designated by a dot alone). Traditionally, the second level domain was the name of the company or the name used on the internet. The third level was commonly used to designate a particular host server. Therefore, ''ftp.wikipedia.org'' might be an FTP server, ''www.wikipedia.org'' would be a World Wide Web Server, and ''mail.wikipedia.org'' could be an email server. Modern technology now allows multiple servers to serve a single subdomain, or multiple protocols or domains to be served by a single computer. Therefore, subdomains may or may not have any real purpose. OFFICIAL ASSIGNMENT ICANN (Internet Corporation for Assigned Names and Numbers) has overall responsibility for managing the DNS. It controls the root domain, delegating control over each top-level domain to a Domain Name Registry . For CcTLDs , the domain registry is typically controlled by the government of that country. ICANN has a consultation role in these domain registries but is in no position to regulate the terms and conditions of how a domain name is allocated or who allocates it in each of these country level domain registries. On the other hand, Generic Top-level Domain s (gTLDs) are governed directly under ICANN which means all terms and conditions are defined by ICANN with the cooperation of the gTLD registries. Domain names which are theoretically leased can be considered in the same way as real estate, due to a significant impact on online brand building, advertising, search engine optimization, etc. A few companies have offered low-cost, below-cost or even free domain registrations, with a variety of models adopted to recoup the costs to the provider. These usually require that domains are hosted on their site in a framework or portal, with advertising wrapped around the user's content, revenue from which allows the provider to recoup the costs. When the DNS was new, domain registrations were free. A domain owner can generally give away or sell infinite Subdomain s of their domain, e.g. the owner of example.edu could provide domains that are subdomains, such as foo.example.edu and foo.bar.example.edu. USES AND ABUSES As domain names became attractive to marketers, rather than just the technical audience for which they were originally intended, they began to be used in manners that in many cases did not fit in their intended structure. As originally planned, the structure of domain names followed a strict hierarchy in which the top level domain indicated the type of organization (commercial, governmental, etc.), and addresses would be nested down to third, fourth, or further levels to express complex structures, where, for instance, branches, departments, and subsidiaries of a parent organization would have addresses which were subdomains of the parent domain. Also, hostnames were intended to correspond to actual physical machines on the network, generally with only one name per machine. However, once the World Wide Web became popular, site operators frequently wished to have memorable addresses, regardless of whether they fit properly in the structure; thus, since the .com domain was the most popular and memorable, even noncommercial sites would often get addresses under it, and sites of all sorts wished to have second-level domain registrations even if they were parts of a larger entity where a logical subdomain would have made sense (e.g., abcnews.com instead of '''news.abc.com'''). A Web site found at The popularity of domain names also led to uses which were regarded as abusive by established companies with trademark rights; this was known as Cybersquatting , in which somebody took a name that resembled a trademark in order to profit from traffic to that address. To combat this, various laws and policies were enacted to allow abusive registrations to be forcibly transferred, but these were sometimes themselves abused by overzealous companies committing Reverse Domain Hijacking against domain users who had legitimate grounds to hold their names, such as their being generic words as well as trademarks in a particular context, or their use in the context of fan or protest sites with free speech rights of their own. Laws that specifically address domain name conflicts include the Anticybersquatting Consumer Protection Act in the United States and the Trademarks Act , 1999, in India. Alternatively, domain registrants are bound by contract under the UDRP to comply with mandatory arbitration proceedings should someone challenge their ownership of the domain name. GENERIC DOMAIN NAMES — PROBLEMS ARISING OUT OF UNREGULATED NAME SELECTION Within a particular top-level domain, parties are generally free to select an unallocated domain name as their own on a first come, first served basis, resulting in Harris's Lament , ''all the good ones are taken''. For generic or commonly used names, this may sometimes lead to the use of a domain name which is inaccurate or misleading. This problem can be seen with regard to the ownership or control of domain names for a generic product or service. By way of illustration, there has been tremendous growth in the number and size of Literary Festival s around the world in recent years. In this context, currently a generic domain name such as ''literary.org'' is available to the first literary festival organisation which is able to obtain registration, even if the festival in question is very young or obscure. Some critics would argue that there is greater amenity in reserving such domain names for the use of, for example, a regional or umbrella grouping of festivals. Related issues may also arise in relation to non-commercial domain names. UNCONVENTIONAL DOMAIN NAMES Due to the rarity of one-word dot-com domain names, many unconventional domain names, Domain Hack s, have been gaining popularity. They make use of the top-level domain as an integral part of the Web site's title. Two popular domain hack Web sites are Del.icio.us and Blo.gs , which spell out "delicious" and " Blog s", respectively. Unconventional domain names are also used to create unconventional email addresses. Non-working examples that spell 'James' are j@m.es and j@mes.com, which use the domain names m.es (of Spain's .es ) and mes.com, respectively. COMMERCIAL RESALE OF DOMAIN NAMES An economic effect of the widespread usage of domain names has been the resale market (after-market) for generic domain names that has sprung up in the last decade. Certain domains, especially those related to business, gambling, pornography, and other commercially lucrative fields of digital world trade have become very much in demand to corporations and entrepreneurs due to their importance in attracting clients. |
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