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What is a DNS server?

Domain Name System is a popular approach used in the translation of domain names to their IP addresses. This system maps each domain name with the IP address stored against them. This way, users never need to recall the IP address of each website. In this article, we will be going through the DNS servers along with other relevant concepts of it. 

General Jan 31, 22 by Nisal N 7 min Read
What is a DNS server?

What is DNS

Domain Name System(DNS) is a client-server model that aims at mapping the domain names to the IP addresses. Users don't need to remember the IP address of each website but can refer to the IP address using the domain name. For instance, when you type "www.example.com" in the address bar and hit enter, the first task is to map the domain name to the IP address. This procedure is called "translation".

Domain names are alphabetical, making them easier to remember than the stream of numbers in an IP address. When you use a domain name, the DNS service converts the name to the corresponding IP address, making the web address more convenient. Reverse lookup is a strategy where we query the domain names associated with the specified IP address.

What is the IP address?

An IP address is a unique combination of digits for a device connected to the internet. An IP address can also exist within the same Local Area Network IP stands for "Internet Protocol", which is a set of protocols that handles the format of data and what principles the users and network engineers must follow when the data is transmitted over the internet or a local network.

An IP address is a sequence of digits separated by dots. Each IP address block is represented by a four-digit permutation, such as 192.158.1.38. Each integer in the set can have a value between 0 and 255. As a result, the IP addressing range extends from 0.0.0.0 to 255.255.255.255.

The Internet Assigned Numbers Authority (IANA), a division of the Internet Corporation for Assigned Names and Numbers (ICANN), assigns IP addresses to each device. It is a non-profit organization founded in the United States in 1998 to help preserve the security and accessibility of the internet.

IP addresses are also helpful in transferring files over the network, especially while working with virtual machines. The IP4 address scheme has four sections where each value ranges from 0 to 255. 

The IP address can be either dynamic or static. A static IP address scheme does not change the address, while a dynamic address scheme keeps changing the address. A static address scheme is usually used for computer engines and live gaming, where a static IP address is required

What is a DNS server?

A DNS server is a giant database of domain names that are mapped to IP addresses. Consider them as a phone book where you don't need to remember the contact number of each person but can get it using the contact name saved against it. There can be multiple DNS servers for each ISP. DNS servers communicate with one another by exchanging domain names, IP addresses, or pointers to other DNS servers that are authoritative for that domain.

Types of DNS servers

DNS recursive resolver

This is the first gateway that interacts with the client request. This server acts as a middleman between the client and DNS nameserver. It either returns cached data or will forward the request to the root name server.

DNS root nameserver

A root server accepts a recursive resolver's request containing a domain name. This server responds by directing the recursive resolver to a TLD nameserver based on the domain's extension. The extension can be.com,.net,.org, and so on. The Internet Corporation for Assigned Names and Numbers (ICANN) manages the root nameservers.

TLD nameserver

This server contains information related to the common extension domain names. For instance, the ".net" server includes information on all the domain names having this extension. 

 Authoritative DNS server

The authoritative nameserver has information specific to the domain name it serves (examples.com) and provides the IP address of the requested domain name to the recursive resolver. A DNS server is the authoritative (point of origin) server for the DNS zone whose data you're looking for. A non-authoritative server must go to the authoritative server for the answer, which is typically cached for a set period.

How DNS servers work

The client-server network architecture underpins DNS. When you navigate through websites, your web browser acts as a client (DNS Resolver), requesting DNS servers from your ISP (internet service provider). to determine whether the domain name is resolved on a server.

When a DNS server receives a request, it temporarily assumes the role of a DNS client. If the address cannot be resolved, the server forwards the request to another DNS server, and the process is repeated until the request reaches a server with a matching IP address. The response is then routed through the DNS server chain to the original client, your browser. The DNS resolver is the client-side of the DNS resolution mechanism that requests the translation of a given domain name. The DNS server then fully resolves the domain name (translation). DNS resolvers are typically divided into three types: 

  • recursive
  • non-recursive
  • Iterative.

A resolver can also be a combination of several of them. DNS is a protocol in and of itself, and it does not make use of HTTP GET or POST requests. The DNS protocol can communicate via UDP or TCP. UDP is preferred for regular queries because most requests and responses are small in size, and the DNS server is usually set up by the ISP that is "closer" to the user, with fewer hops in between.

DNS server zones and records

A DNS Zone is an administrative control unit. It has a domain and possibly multiple subdomains, as well as at least three DNS records - the SOA (Start of Authority) record and two NS (Name Server) records. In practice, a zone is a collection of DNS records that are managed as a unit.

A DNS record is a single item that describes a specific item or feature of a zone. Several examples -

A record - one of the essential records in DNS, it connects a name (such as www(.)example(.)com) to an IPv4 address (say 192.168.1.1)

The AAAA record is similar to the A record but with an IPv6 address.

How to optimize the DNS query

We can cache the results locally in order to reduce the effort put on the DNS servers. The results that we get from the servers have the Time-to-Live (TTL) associated with it. This determines after what time we need to discard or refresh the results.

Conclusion

In this article, we went through the details of DNS servers and saw how they solve a significant problem in the networking world. We saw how they have a sequence of servers that contribute to the translation of domain names to IP addresses. IP addresses are unique identifiers of each machine on the internet. Since it is not possible for an average human to memorize the addresses of all the machines in the global network, we use DNS to help us here. The DNS also has a caching feature to ensure that the servers suffer minimal load while translating the domain names.

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Nisal N

Computers has always fascinated me since I was a kid and here we are. I love travelling for 2 reasons: the first one to see a new part of the world and second (the most important one) to experience the rich culture hidden among the country and people. I'm pretty good at cooking but very poor when it comes to baking.

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