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DNS: name resolution on the Internet

You need the IP address of a server on which your website is registered to be able to load a page into the World Wide Web. In general, only the domain name is familiar to you, and for good reason. Indeed, a sequence of numbers such as forms the basis of communication on the Web but remains difficult to memorize. This is why each IP address is equivalent to a domain name. Here is how it is formed:

IP address:


The translation of a domain name into a numeric address is called name resolution, which is an Internet service made available to the Domain Name System (DNS).


  • What is DNS?
  • DNS query
  • What is a DNS server?
  • DNS error

What is DNS?

The domain name system is a hierarchical directory system which is used to manipulate the domain namespace. The primary mission of this service is to respond to requests for name resolutions. The DNS has the same objectives as a telephone information service. It makes all the contacts available and publishes them on request. To do this, the system uses an international network of DNS servers which subdivide the domain namespaces independently in administered zones. This allows for decentralized manipulation of domain name information. Each time a user registers a domain name, a new entry is indicated in the relevant directory. This takes the form of a Resource Record (RR) in the DNS. The database of a DNS server thus corresponds to a collection of all the resource records of a domain namespace area for which the server is responsible.

When the domain name system was created in 1983, it took more than one error process based on a local hosts file to successfully complete the name resolution. It is still possible today to find the file host.txt on Unix systems in the etc / directory and on Windows computers under% SystemRoot% \ system32 \ drivers \ etc. At the time, the host.txt program had to be processed manually and updated at regular intervals. This process required patience and became more and more difficult to carry out due to the dazzling growth of the Web. Today, host.txt is only useful for assigning IP addresses in local networks. Furthermore, thanks to these files, it is possible to block Web servers by automatically redirecting corresponding addresses to localhosts.

DNS query

Each time you enter a web address in the form of a URL (Uniform Resource Locator) in your browser’s search bar, it returns this request to the resolver. It is a special component of your operating system that has stored IP addresses already loaded in your cache and which provides client applications if necessary. If a requested IP address is not present in the resolver cache, the new DNS request is then forwarded to the responsible DNS server. Typically, this is the DNS server of your Internet service provider. From there, the request is balanced with the DNS database, which results in a response from the IP address (“forward lookup”), if this is present. This allows your browser to address the desired web server clearly and only via the web. The alternative is that the IP addresses translate in the opposite direction with respective domain names (“reverse lookup”). If a DNS server cannot respond to a request due to its own data store, it can then retrieve the corresponding information from another server or forward the request to the relevant DNS server. We speak in this case of recursive and iterative queries.

  • Recursive queries: if the DNS server cannot respond to a query itself, the latter retrieves the desired information from another server. The resolver then returns the entire DNS request to the affected server. This last book gives the resolver the answer as soon as the domain name is resolved.
  • Iterative queries: if a DNS server cannot respond to a query, the latter only responds with the address of the next DNS server queried. The resolver must handle these requests independently until the domain name is resolved.

The central management of domain information in the DNS is characterized by certain reliability but also by flexibility. If the IP address of a server changes, the user is generally not warned since the domain name is assigned only to an IP address in the database.

What is a DNS server?

As far as DNS servers (or name servers) are concerned, this is special software which uses a DNS database in order to respond to queries concerning domain namespaces. Since DNS servers are usually located on dedicated hosts, the computers that host these programs are also called DNS servers. In the DNS system, we differentiate between authoritative and non-authoritative servers.

  • Authoritative DNS server: a server is called authoritative because it saves secure information which concerns a particular zone of the domain namespace in its DNS database. The DNS is constructed so that each zone has at least one authoritative server. Such a system is generally implemented as a cluster of servers (clusters) on which data from identical zones is recorded on a master system (masters) and on several slaves (slaves). In this case, we are talking about a primary and secondary name server. This kind of redundancy allows, on the one hand, to further secure the system in the face of failures and, on the other, to improve the availability of an authoritative name server.
  • Non-authoritative name server: if the DNS information for a name server does not come from a clean zone file but from a third party, this is then considered to be a non-authoritative name server (for the corresponding information). Such a situation arises if a name server cannot respond to a request due to its own data store. It then retrieves the information from another name server (recursion). This DNS data is temporarily stored in local working memory (caching) and is delivered during other connections. Since these entries cannot have changed in the zone file in the given interval, this unauthorized name server DNS information is not considered secure.

DNS error

During network problems, it is common to receive the following error message: ” the DNS server is not responding “. The connection to the Internet is damaged in this case and the Internet page cannot be loaded.

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DMT Web Hosting is too concerned about the health and safety of both clients and employees. Our office is closed due to countrywide lock down. You can reach us on +92 300 044 4656, +92 321 112 6660 during the lock down period. We appreciate your understanding and patience.