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Domain Names and the Domain Name System (DNS)


Every device that connects to the Internet is assigned a numerical address called an IP address (32 bit number in 4 units). The problem with IP addresses are twofold:

  1. They are difficult to memorise.
  2. If the physical location of a resource changes, so does the IP address.

Therefore, it became apparent there was a significant drawback to relaying solely on IP addresses to find hosts (information) on a computer network. ARPANET (forerunner to the Internet) solved this problem by assigning hostnames to host computers. Hostnames were alphabetical characters that were easily memorised. The Network Information Center (NIC) was the first authority to assign hostnames, and distributed a list of hostnames in a text file named: HOSTS.TXT. The problem with this system, was that, each node (location) that connected to ARPANET had to manually update the HOSTS.TXT file. This became a problem as more and more nodes were added to ARPANET.

The solution to this problem arrived in 1983, when Paul Mockapetris proposed the creation of the Domain Name System (DNS). The Domain Name System was implemented in 1984, and it would become a centralised location that distributed 'names' and resolved naming issues on TCP/IP networks (ARPANET and the Internet etc). The specification of the Domain Name System was included in the following RFC documents: RFC 882, RFC 883, RFC 1034 and RFC 1035.

Due to the Network Information Center's (NIC) experience with administrating hostnames, the Defense Data Network Network Information Center (DDN-NIC) would be created, in 1984, to assign and handle the registration of names within the Domain Name System. IANA, created by Jon Postel, while he worked at the Information Sciences Institute (ISI), would administer the root zone of the Domain Name System (highest level), but DDN-NIC would control the registration of names within the top-level domains - com, edu, gov, mil, org, net, and us.

In 1990, the Internet Activities Board (IAB) proposed a change to the centralised control of the Domain Name System (DNS) by IANA and NIC. While IANA would continue to manage the root zone of the DNS, management of the top level domains would transfer from NIC to Government Systems (GSI). In 1992, InterNIC (created by NSF) outbidded GSI to take control of the top level domains. In 1998, ICANN was created, a nonprofit organisation, ICANN (IANA became a department of ICANN) would have authority over the DNS root zone and the top level domains of the DNS.

Introduction to the Domain Name System (DNS)

The Domain Name System is comprised of domain names: domain names are alphabetical character strings that are memorable and static. Domain names are unique and allow host computers to create a identity based upon their domain name. Domain names can be assigned to an IP address, and the IP address assigned to a domain name can be changed. This means that the data of a domain name can be moved to another physical location, and the data can still be located by using the same domain name. This means that end-users can locate a resource by only knowing it's domain name.

Present day, the Internet is comprised of two namespaces:

  1. IP addresses
  2. Domain name addresses

The Domain Name System (DNS) does the following:

  1. Links a domain name to a server (using an IP address)
  2. Stores information about domain names.

Management and Maintenance of the Domain Name System

Due to the importance of the Domain Name System (DNS), management and maintenance is required. While the Internet has no central government, the assignment of "space" (IP, DNS, ASN) on the Internet is strictly managed. The Domain Name System is currently (2014) managed by a hierarchy of government agencies and commercial companies:

  1. (DOC) United States Department of Commerce
  2. (NTIA) National Telecommunications and Information Administration
  3. (ICANN) Internet Corporation for Assigned Names and Numbers
  4. (IANA) Internet Assigned Numbers Authority
  5. Internet registries (like Verisign)
  6. Internet registrars

The Domain Name System (DNS) was created in 1983 by Paul Mockapetris. The Domain Name System is a hierarchical system, and at the top of the hierarchy is the DNS root zone. Implemented in 1984, the DNS root zone (highest level) was administrated primarily by IANA from 1984-1998; Jon Postel was the head of IANA during this period. From 1984-1990, the Network Information Center (NIC) administrated the top level domains of the DNS. From 1990-1998, the top level domains of the DNS were administrated by a number of different companies.

The IANA/NIC dominance of the DNS dramatically changed in 1998. Jon Postel caused controversy when he instructed eight root nameservers to change the root server they "pulled" addresses from; essentially hijacking control of the Internet. In response, the NTIA created a document named: "A proposal to improve technical management of Internet names and addresses". This document led to the creation of ICANN. IANA became a department of ICANN in 1998. The US government was obviously alarmed by the "power" Jon Postel (who created IANA, alongside Joyce Reynolds) yielded upon the Internet, and since 1998, IANA is overseen and compiles with NTIA policies.

ICANN is a nonprofit organization that is under contract to the Department of Commerce of the United States. The NTIA is an agency within the Department of Commerce of the United States, and oversees the contract that the Department of Commerce has with ICANN. ICANN has authority over the DNS root zone, and, by extension, it's top level domains. IANA became a department of ICANN in 1998, and manages the DNS root zone. IANA delegate responsibility for managing international Internet numbers to five regional Internet registries, who comprise the Number Resource Organization.

There is a demand - supported by many of the pioneers of the Internet - to transition control of the DNS and IP addresses from US government control to a global multi-stakeholder community. In 2013, the 'Montevideo Statement on the Future of Internet Cooperation' was released: signed by leaders of many important Internet organisations, it warned against NSA surveillance of the Internet, and urged for greater international oversight of the Internet.

Hierarchy of Domains

The domain name system is structured in hierarchical levels, which are:

  1. DNS root domain
  2. Top level domain (includes gTLD and ccTLD)
  3. Second level domain
  4. Third level domain

The DNS root domain is the highest level within the domain name system; all levels below the root domain are subdomains of the root domain. The DNS root domain is name-less. The root domain is maintained by the Internet Assigned Numbers Authority (IANA). Namespace within the root domain is therefore created by IANA, and the namespace they create is called the top level domain (com, org, gov).

IANA does not maintain the top level domains: instead it assigns authority to manage top level domains. Top level domains are maintained by registries; these registries usually offer to sell namespace within their domain. Verisign, for example, are the registry for the com top level domain, and therefore sell namepace (such as google.com) to the general public.

Information about the namespace for each domain is stored in a nameserver. The role of nameservers is also to translate domain names into IP addresses. The highest level nameservers are root nameservers; the root nameservers (there are 13 root server clusters) can be found at: root-servers.org. The information (data) found in the root domain is maintained by the Internet Assigned Numbers Authority (IANA).

The root nameservers store information about the top level domains. If someone queried a root nameserver for the location of google.com, the root nameserver would probably not contain this information, but it would know the nameserver which did: the nameserver for the com top level domain. Therefore, below the root nameservers, there is a hierarchy of nameservers which store and translate domain names for top, second and third level domains. Some of these nameservers are referred to as: authoritative nameservers and caching nameservers. The question may arise as to why all domain queries are not routed through the root nameservers? for performance, the root nameservers could not handle billions of requests, and, therefore, domain name resolvers are used to route the domain queries to a hierarchy of nameservers.

Domain Names and their Syntax

A domain name is a namespace within a domain. For example, google.com, google is a namespace within the com domain, and com is a namespace within the nameless root domain. Google is also a subdomain of com, and com a subdomain of the root domain.

While a domain name can include one label - such as com - in general usage they contain two or more labels. Labels are separated by dots (.). The importance of the label - in terms of it's hierarchy within a domain name - moves from right to left. Each label, which is to the left, can be described as a subdomain of the label to it's right.

A domain name with two labels is: google.com

Moving from right to left we can see that com is the top level (domain) and google is the second level (domain). In theory, there is no end to the amount of domain name levels, for example you could have the domain name: example.co.ss.co.com. Domain names are used within larger online addresses: such as a URL. Domain names can also be hostnames.

Registering and Managing Domain Names

As stated, the top level domains (namespace within the root domain) are managed (some may say owned) by registries. These registries are assigned by IANA (who maintain the root domain above top level domains). Therefore, the end-user cannot register a top level domain, but they can register a namespace within it; which will be a second level domain (such as the namespace google within the com domain). The com domain registry is Verisign. However, some domain name registries (like Nominet for the uk ccTLD) impose third level domains, for example: co.uk, ac.uk. This means that an end-user cannot register a second level namespace within the uk top level domain.

The registration of domain names - to the general public - is usually conducted by registrars; who are accredited by the ICANN. ICANN (of which IANA is a part) maintains the hierarchy of the domain name system. Registrars register domain names on behalf of end-users. Registrars have to pay a fee to a registry of a domain name: the registrar godaddy would have to pay a fee to Nominet to register a namespace within the uk top level domain. End-users usually cannot contact registries directly to register a domain name: instead the registrar does it on their behalf, and also manages the domain name for them.

When registering a domain name, the following details will need to be provided:

  1. Registrant details: registrant name and address.
  2. Registrar details: contact details for technical issues.
  3. Billing address (usually of the registrant) for renewing the domain name.
  4. Name servers: controls the DNS of the domain name.

End-users can register namespace within a range of top level domains: com being the most popular. Top level domains are continually being created; the original top level domain names were: com, net, org, mil and gov. Due to the popularity of the Internet increasing, further top level domain's were added, for example: info. If an end-user is interested in registering a domain name: then they can check if it is available by conducting a whois (read more: whois privacy) search at a registrar. If the domain name is available, then it can be registered with a registrar; there are currently (2014) over 900 accredited ICANN registrars. Resellers, third party companies, sometimes sell domains on behalf of an accredited registrar.

Abuse and Disputes

Abuse of domain names and the domain name system has occurred. Cyber squatting is the most obvious abuse; where end-users buy a domain name just so that another interested "party" cannot, and then, either extort a fee to sell it, or hold onto it out of spite (the ethical version of cyber squatting is DNS parking: registering a domain name with the intention of using it in the future).

Domain name disputes occur for a multitude of reasons: when a registrar goes out of business; cannot be contacted; or purposely/mistakenly registers domain names in it's own name, rather the registrant's. ICANN publish guidelines for registrar's and they accredit registrar's; therefore, ICANN is the ultimate authority for resolving disputes for gTLD's. For ccTLD's (like the uk domain administered by Nominet) guidelines and disputes are resolved by the country code manager.

Transfer a Domain Name

As previously discussed, end-users have to register domain names through accredited registrars. The registrar is a "middle man" who contacts the manager (registry) of a domain to purchase a namespace - at that domain - on behalf of the end-user. Registrars also manage the domain name on behalf of the end-user; renewing the domain and alteration to the DNS record. Some registrars allow full DNS control of a domain name, while others do not. ICANN - who accredit registrars - allow end-users (registrants) to switch registrars; which is outlined in their 'The Inter-Registrar Transfer Policy'. The current manager (registrar) of a domain name can charge a fee for transferring a domain name to another registrar. The process for transferring domain names does vary slightly for each type of domain. The 'Initial Authorization for Registrar Transfer form' is used for transferring a range of gTLD's (not mil and gov domains), but, the IPS TAG is used by Nominet to switch uk ccTLD's.

Further reading: Transferring a co.uk domain name address


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