What is a DNS Le Geek Moderne

What is a DNS ?

Conceived in 1983, the DNS (Domain Name System) has significantly contributed to the development of the Internet. This distributed service has indeed simplified the resolution of server names on the Web. In practice, the system has made it easier to associate domain names with IP addresses.

It thus promotes the integration of new entries and the search for hosts already present on the network.

What is the role of a DNS server ?

The role of a DNS server can be summarized as resolve domain names. However, this function is quite difficult to understand without first knowing what is a DNS. To understand this system, the easiest way is to put it together with a directory.

Only the DNS associates a domain name and an IP address, instead of a person and a phone number.

Every day, you use domain names to access information on the Internet. They are presented in the form ” site.com “, ” website.org “, ” site.en “… Your browser, on the other hand, refers to IP addresses to interact with the site’s servers. They are formed by 4 groups of decimal numbers from 0 to 255 in IPv4.

The addresses are changed to 8 groups of hexadecimal values with the IPv6 protocol.

After 9, this type of numbering uses the letters from A to F to complete the system in base 16. You will have 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F before returning to 0. These codes are quite complicated for Internet users, but suitable for computers. They offer a myriad of possible combinations and even more with IPv6.

The DNS server thus plays the role of translator between the name and the IP.

What are the types of DNS queries ?

The DNS queries allow forindicate to the servers the nature of the request and the information sought. They generally take three forms, namely recursive, iterative and non-recursive. With the recursive query, the resolver sends a request to obtain an IP address or confirm its absence from the DNS server.

On an iterative query, the DNS client authorizes the return of the most relevant answer possible. The queried server will thus provide a recommendation, If it does not find a match. It often directs to an authoritative server or a TLD (top level domain) server.

If there is no result, the recommended authority will return to another level of servers. The iterative process will continue until a satisfactory answer is obtained or the timeout (timeout).

Finally, a non-recursive request is issued when the resolver starts to query the DNS server on an address at its disposal. It has access from the start, if it is the reference server for the DNS record. The answer can also be stored in its cache.

In these cases, sending a new request is not necessary. A previous answer can be reused, thus avoiding server overload and bandwidth overuse

How a DNS query works ?

It is important to understand how the lookup system works to answer the question ” what is a DNS ? “. Basically, the DNS matches a domain name to a specific IP address. However, this operation is not so simple and involves several steps in the background. The complexity of the process caused the Facebook outage of October 2021, when its DNS servers have become untraceable.

Concretely, you send a first request to a recursive DNS resolver by entering an address in your browser. The recursive resolver of your ISP or company will start with query a DNS root server. The latter will direct the query to the address of a TLD (top level domain) server such as ” .com”, ” .org”, ” .net ” ..

The TLD redirect then the DNS request to the dedicated domain name server, for example “site.net “. At this point, the resolver should obtain the IP address of the requested site and transmit it to your Internet browser. Your software will be able to send a reply to your requestHTTP request and receive the content to display from the platform’s servers.

What DNS query should I enter to find out which DNS servers ?

You need to use the command interface to know your DNS server. Under Windows, you can open it by clicking on Start, All programs, Accessories, then Command prompt. Then enter the line: ipconfig/all | findstr ” DNS Servers. You can also remove the filter and use “ipconfig. However, you will have to look up the DNS among all the data displayed.

This is the default DNS address of your router or ISP. If you preferred to configure the DNS server, you will be directed to the address chosen for your. It is also possible to customize the DNS on a router.

As a result, the answer obtained does not necessarily correspond to the DNS server of your ISP. Everything will depend on your installation.

You can also discover your DNS server with the command : nslookup [ip address]. By the way, the command line “nslookup” resolves DNS names on all operating systems. You just have to open the equivalent of the Windows CMD in the OS you are using.

In any case, the tool will provide you with the name and address of the DNS.

What DNS query should I enter to find out the DNS servers?

The difference between public and private DNS

The question ” what is a DNS ? “You can discover the basics about domain names. However, this system is complex because of the security and convenience requirements of users. The Internet is also made up of open and closed networks.

In this context, do not confuse public and private DNS.

By definition, an public DNS server is accessible to all and does not require any authentication. It is therefore open to the public Internet and does not use a firewall to limit access. A private DNS server is, on the other hand, associated with an IP park servers and to a closed network. Thus, users can not access it from the Web.

This architecture usually includes a firewall, domain controllers and several private servers (mail server, application server, file server, etc.).).

You can also find a private DNS on a VPC (Virtual Private Cloud). However, you should pay special attention to the configuration, if you intend to use an API. This architecture indeed requires some expertise to avoid resolution errors.

Nevertheless, cloud computing offers often provide technical support for this kind of operation.