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What is DNS?

DNS (Domain Name Server) is the system used in Internet to be able to assign and universally use unequivocal names to refer to systems connected to the net. Thus both human users and applications can used DNS names instead of the numeric addresses of the IP net. This represents great advantages, among others the fact that it is easier and less burdensome for us to use names and not
numbers and it allows an organization to make the name of machines, services, email addresses etc independent from the specific number addresses which working systems may have at a given time in function of changing elements such as the topology of the net and the provider of access to Internet.

Technically DNS is an immense data base distributed hierarchically throughout Internet: there are innumerable servers which interact among themselves to find and provide for the customer applications which consult them the translation of a name to its associated PI address, to which the desired connexion may be made. Each part of the data base has a replica in at least two servers and this
ensures the proper redundancy factor.

The reason which motivated the development and implementation of DNS in Internet was the great growth in the number of machines connecred. Previously, the link between numbers and IP addresses was made via lists kept centrally is a single file (Host.txt) which had to be constantly updated with each new system connected up and to be present in all the computers connected to Internet.

The maintenance of this system became unviable when the number of connected systems reached a few thousand in the mid 1980s.

What is its objective?

The objective of DNS is to allow the scaling down, from both the administrative and technical points of view, of the system of Internet names by means of a hierarchical distribution of delegated domains. The domains are administrative entities the object of which is to divide up the management load of a central administrator and share it out among the subadministrators. The latter in their turn may repeat the process if the volume of the domain to be administered makes this advisable.

At the first hierarchical level are the "Top Level Domains" or TLDs which are one per country (two letter domains which correspond to the ISO-3166 code for each territory) plus the special 3 letter domains: "edu", "com", "gov", "mil", "org", "int" and "net".

In general the hierarchical structure of DNS tries to reflect administrative dependencies administrativas under a first geographical component (or activity component in the case of the "special" TLDs); for instance, a machine or service belonging to a department or branch of an organization in France will have a name of the type:

Each TLD has its own regulations which say who can and who cannot register a second level domain, which domains are allowed, which procedures are to be followed etc. The fact that someone satisfies the requirements to register a domain under one TLD does not mean that he satisfies them to register this or another domain under another TLD.


One of the main functions of the ANDORRAN TELECOMMUNICATIONS SERVICE is to register the names of second and third level DNS domains under "ad" for use on the Internet by Andorran organizations. This document contains the regulations and procedures governing the registration of second and third level DNS domains under "ad".

To find out who the contact persons for a second level domain existing and delegated under "ad" are, you can consult the data base of the ANDORRAN TELECOMMUNICATIONS SERVICE, EXISTING DOMAINS.







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