All About Domain
Domain registration is the process by which a company or individual can secure a website domain, such as www.yoursite.com. Once you have completed domain registration the domain becomes yours for the period of the contract, usually one year. Before registration expires it must be renewed, or the domain reverts back to being available to the general public.
The Internet Corporation for Assigned Names and Numbers (ICANN) manages the international Domain Name Server (DNS) database. ICANN insures that all registered names are unique and map properly to a unique Internet Protocol (IP) address. The IP address is the numerical address of the website that tells other computers on the Internet where to find the server host and domain.
Domain registration is available to the public via a registrar. Fees and services vary from company to company, but the process is generally inexpensive. Before a domain registration can be approved, the new name must be checked against existing names in the DNS database. The online registrar provides a field into which you can enter your desired name and hierarchy —- that is, the letters that come after the "dot." Familiar hierarchies are .com, .net, .org, .name, .info and .biz. If the name is not already taken, it is available for domain registration.
During the domain registration process, you will be required to give contact information that will be publicly available through the WHOIS database. Anyone can go to a WHOIS search engine and enter a domain name to see who has registered it. Registrars require that this information be accurate and true. If you feel uncomfortable providing personal information, there are some registrars that will act as your proxy, supplying their information in place of your own as the contact for the domain. There may be a small fee for this service and potential drawbacks to balance against the ability to maintain your privacy, so read the Terms and Conditions carefully before deciding to opt for a domain by proxy.
Also important, be sure you will own the domain name, as some registrars maintain control over the domains they register. And be sure you retain the option to transfer the domain to another registrar, if you wish. There might be an initial period after which this becomes possible. Look for any fees that might be incurred as a result of transferring the domain. This could become important down the road if you wish to take advantage of another registrar's products or services.
Upon completing the domain registration process, it will take a period of hours to a few days to be able to see the domain online. The domain can be "parked" with an "in construction" page that acts as a kind of placeholder. Parking a domain is very inexpensive and most registrars offer this service for a small fee to give you time to come up with content. Once a registrant is ready to supply content, a web server must host the domain. The registrar might also provide hosting services, or you may wish to transfer your domain to another web hosting company.
If you are considering domain registration, ICANN recommends dealing with an accredited registrar. These registrars have entered into an official agreement with ICANN to meet minimal requirements for providing domain registration. For more information about domain registration, and for a list of accredited registrars, see the ICANN site.
Every domain name has a suffix that indicates which top level domain (TLD) it belongs to. There are only a limited number of such domains. For example:
Because the Internet is based on IP addresses, not domain names, every Web server requires a Domain Name System (DNS) server to translate domain names into IP addresses.
A domain name is an identification label that defines a realm of administrative autonomy, authority, or control in the Internet, based on the Domain Name System (DNS).
Domain names are used in various networking contexts and application-specific naming and addressing purposes. They are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, net and org, and the country code top-level domains (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users that wish to connect local area networks to the Internet, run web sites, or create other publicly accessible Internet resources. The registration of these domain names is usually administered by domain name registrars who sell their services to the public.
Individual Internet host computers use domain names as host identifiers, or hostnames. Hostnames are the leaf labels in the domain name system usually without further subordinate domain name space. Hostnames appear as a component in Uniform Resource Locators (URLs) for Internet resources such as web sites (e.g., en.wikipedia.org).
Domain names are also used as simple identification labels to indicate ownership or control of a resource. Such examples are the realm identifiers used in the Session Initiation Protocol (SIP), the DomainKeys used to verify DNS domains in e-mail systems, and in many other Uniform Resource Identifiers (URIs).
An important purpose of domain names is to provide easily recognizable and memorizable names to numerically addressed Internet resources. This abstraction allows any resource (e.g., website) to be moved to a different physical location in the address topology of the network, globally or locally in an intranet. Such a move usually requires changing the IP address of a resource and the corresponding translation of this IP address to and from its domain name.
Domain names are often referred to simply as domains and domain name registrants are frequently referred to as domain owners, although domain name registration with a registrar does not confer any legal ownership of the domain name, only an exclusive right of use.
This article primarily discusses the group of domain names that are offered by domain name registrars for registration by the public. The Domain Name System article discusses the technical facilities and infrastructure of the domain name space and the hostname article deals with specific information about the use of domain names as identifiers of network hosts.
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.[1] 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.[2] 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 June 2009, there are 20 generic top-level domains and 248 country code top-level domains.[3] 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,[4] 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.[5] Observers believed that the new rules could result in hundreds of new top-level domain to be registered.[6]
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] Second-level and lower level domains
Below the top-level domains in the domain name hierarchy are the 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.
Next are third-level domains, which are written immediately to the left of a second-level domain. There can be fourth- and fifth-level domains, and so on, with virtually no limitation. An example of an operational domain name with four levels of domain labels is www.sos.state.oh.us. The www preceding the domains is the host name of the World-Wide Web server. Each label is separated by a full stop (dot). 'sos' is said to be a sub-domain of 'state.oh.us', and 'state' a sub-domain of 'oh.us', etc. In general, subdomains are domains subordinate to their parent domain. An example of very deep levels of subdomain ordering are the IPv6 reverse resolution DNS zones, e.g., 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa, which is the reverse DNS resolution domain name for the IP address of a loopback interface, or the localhost name.
Second-level (or lower-level, depending on the established parent hierarchy) domain names are often created based on the name of a company (e.g., microsoft.com), product or service (e.g., gmail.com). Below these levels, the next domain name component has been 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, each intended to perform only the implied function. Modern technology allows multiple physical servers with either different (cf. load balancing) or even identical addresses (cf. anycast) to serve a single hostname or domain name, or multiple domain names to be served by a single computer. The latter is very popular in Web hosting service centers, where service providers host the websites of many organizations on just a few servers.
Resale of domain names
The business of resale of previously registered domain names is known as the domain aftermarket. Various factors influence the perceived value or market value of a domain name. Annually tens of millions of dollars change hands in connection with the resale of domains. Large numbers of registered domain names lapse and are deleted each year. On average, more than 25,000 domain names drop (are deleted) every day.
A domain name is a component of a Uniform Resource Locator (URL) used to access web sites, for example:
- URL: http://www.example.net/index.html
- Domain name: www.example.net
- Second-level domain name: example.net
A domain name may point to multiple IP addresses to provide server redundancy for the services delivered. This is used for large, popular web sites. More commonly, however, one server at a given IP address may also host multiple web sites in different domains. Such address overloading is possible through a feature in the HTTP version 1.1 protocol (but not in HTTP 1.0) which requires that a request identifies the domain name being referenced. This enables virtual web hosting commonly used by large web hosting services to conserve IP address space.
Domain Names, IP Address and DNS
Domain Names: Everyone is familiar with domain names, they are the names of the website or the part after the "@" on an email address. These names are used to find a machine (or sometimes, one of many machines) so that you can find the webpage or deliver the email to the correct place- it is the internet equivalent to a postal address.
IP addresses: Every machine or node that can be directly accessed on the internet has a unique IP address. This is a just a big number but to make it easier for humans, it is normally written as four numbers separated by dots (eg. 87.106.82.7). As an aside, for those of you that understand binary, each number is an 8 bit binary number 0-255 making a 32 bit number. As a rough analogy, this can be thought of as the postcode or ZIP code of the postal address. Once you have an IP address of a machine on the internet you can connect to that machine.
DNS (Domain Name Server): A DNS server is a server just like any other server on the internet. The purpose of DNS servers are to translate domain names (postal addresses) into IP addresses (postcode/ ZIP codes). Let's run through an example of what happens when you type www.wight-hat.com into your browser.
1) First of all, your internet provider will have a DNS cache- this is a list of previously obtained IP addresses for various domain names so that commonly used names do not have to be constantly looked up. In this example, we assume that this is the first time that a domain has ever been requested through the internet provider. The ISP (Internet Service Provider) will start from the right hand side and see that it is a ".com". It will go to one of the five top level DNS servers in the world (who's IP addresses are on the record to start with) and ask for the ".com" DNS server. The top level DNS server will provide the IP address for ".com".
2) The ISP will then request the "name servers" for wight-hat.com from the machine at the IP address just obtained (from the ".com" DNS server) and this will return two to seven "name servers" which are the machines that hold information on the whereabouts of wight-hat.com. It will receive one of two name servers, "ns1.wight-hat.com 87.106.82.7" and "ns2.wight-hat.com 64.15.153.83". These are the IP addresses of DNS servers that contain information on wight-hat.com.
3) Suppose the first one is received, "ns1.wight-hat.com 87.106.82.7". The ISP now goes to this IP address and requests "www" for wight-hat.com and receives the IP address 64.15.153.83. The ISP now knows where the machine is for serving the web page www.wight-hat.com.
4) The page www.wight-hat.com is requested from the machine at 64.15.153.83 and the machine responds with the page.
This may seem a little long winded but there is a reason for this. Remember that the ISP has a record of the previous requests? Lets look at what happens when we now send an email to someone@wight-hat.com.
1) The ISP knows the DNS server for wight-hat.com because it is in the cache (the record of previous lookups) and finds the DNS IP address is 87.106.82.7.
2) A request for the MX server (mail server) for wight-hat.com is sent to 87.106.82.7 and the response is that the mail server IP address is 87.106.82.7 (the same machine).
3) The mail is sent to the machine at 87.106.82.7. This machine then places the email in the "someone" inbox ready for collection.
You can see how, by breaking it into stages and caching the results, fewer requests have to be made over time. The cache will only be kept for each entry for a certain amount of time and is then discarded. After this a new request is made and so if the machine that hosts the www.wight-hat.com site changes, the ISP will be not forever look in the wrong place.
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posted by peterdj at
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