The domain name space consists of a tree of domain names. Each node in the tree holds information associated with the domain name. The tree sub-divides into zones beginning at the root zone.
When the Domain Name System was created in the 1980s, the domain name space was divided into two main groups of domains.[3] The country code top-level domains (ccTLD) were primarily based on the two-character territory codes of ISO-3166 country abbreviations. In addition, a group of seven generic top-level domains (gTLD) was implemented which represented a set of categories of names and multi-organizations.[4] These were the domains GOV, EDU, COM, MIL, ORG, NET, and INT.
During the growth of the Internet, it became desirable to create additional generic top-level domains. As of October 2009, there are 21 generic top-level domains and 250 two-letter country-code top-level domains.[5] In addition, the ARPA domain serves technical purposes in the infrastructure of the Domain Name System.
During the 32nd International Public ICANN Meeting in Paris in 2008,[6] ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains." This program envisions the availability of many new or already proposed domains, as well a new application and implementation process.[7] Observers believed that the new rules could result in hundreds of new top-level domains to be registered.[8]
An annotated list of top-level domains in the root zone database is published at the IANA website at http://www.iana.org/domains/root/db/ and a Wikipedia list exists.
[edit] Domain name syntax
A domain name consists of one or more parts, technically called labels, that are conventionally concatenated, and delimited by dots, such as example.com.- The right-most label conveys the top-level domain; for example, the domain name www.example.com belongs to the top-level domain com.
- 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 subdomain of the com domain, and www is a subdomain of example.com. This tree of labels may consist of 127 levels. Each label may contain up to 63 ASCII characters. The full domain name may not exceed a total length of 253 characters.[2] In practice, some domain registries may have shorter limits.
- 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.
[edit] Top-level domains
The top-level domains (TLDs) are the highest level of domain names of the Internet. They form the DNS root zone of the hierarchical Domain Name System. Every domain name ends in a top-level or first-level domain label.When the Domain Name System was created in the 1980s, the domain name space was divided into two main groups of domains.[3] The country code top-level domains (ccTLD) were primarily based on the two-character territory codes of ISO-3166 country abbreviations. In addition, a group of seven generic top-level domains (gTLD) was implemented which represented a set of categories of names and multi-organizations.[4] These were the domains GOV, EDU, COM, MIL, ORG, NET, and INT.
During the growth of the Internet, it became desirable to create additional generic top-level domains. As of October 2009, there are 21 generic top-level domains and 250 two-letter country-code top-level domains.[5] In addition, the ARPA domain serves technical purposes in the infrastructure of the Domain Name System.
During the 32nd International Public ICANN Meeting in Paris in 2008,[6] ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains." This program envisions the availability of many new or already proposed domains, as well a new application and implementation process.[7] Observers believed that the new rules could result in hundreds of new top-level domains to be registered.[8]
An annotated list of top-level domains in the root zone database is published at the IANA website at http://www.iana.org/domains/root/db/ and a Wikipedia list exists.
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