7 Minutes
Last Updated: 01-Dec-2021


How Domain Name System (DNS) Works?

What is DNS?

(DNS) stands for Domain Name System and is considered an Internet Phone Book. It helps people to retrieve information and data from the Internet like NiTime.com or ESPN.com. To find Internet resources, IP addresses can be found via DNS. All devices that can connect to the Internet have a unique IP address. This IP address helps determine the location of the device. IP addresses are complex because of DNS and do not need to be memorized.

How does the DNS work

How does the Domain Name System work?

It changes a computer-friendly hostname to an IP address such as www.example.com to 192.168.1.1. This method is also known as DNS resolution. All devices on the Internet have been assigned an IP address. This address is required to find a suitable Internet device – such as the street address used to search a particular home.

When we enter something in a web browser and a web page starts to load, it shows its translation. So, for a .com web page, a machine-friendly address is a must. To understand the mechanism behind DNS resolution, it is important to distinguish between the DNS queries in the different hardware components. For web browsers, DNS search is "behind the scenes" and does not require interaction with the user's computer other than the initial request.

Web page loading involves 4 DNS servers:

  • DNS recursor:
    The repetitive person can be thought of as a librarian who is said to be looking for a specific book anywhere in a library. A DNS-enabled server has been developed to collect queries from client machines using apps like a web browser. It is then responsible for making extra requests for the satisfaction of the DNS query of the client.
  • Root Name Server:
    The root server is the initial step to translate hostnames into human-readable IP addresses. It can be considered an in a library to identify different racks of books, typically as a reference, it serves to other particular locations.
  • TLD Name Server:
    The TLD (Top Level Domain server) is considered a particular rack of books in the library. This is the next step to find the specific IP address, and the last part of the hostname is hosted (for instance.com, the com is a TLD server).
  • Authoritative Nameserver:
    This final nameserver is considered a dictionary on a book's rack with a specific name translation into its definition. It is the last stop in the query of the nameserver. Moreover, if it could access the desired record, the IP address will be returned for the desired hostname to the DNS Recursor, which made the initial request.

What is the difference between an authoritative DNS server and a recursive DNS resolver?

Recursive DNS resolver and authoritative DNS server belong to the structure of DNS. But both of these servers have different functions and locations in DNS. One of the superficial differences between them is that the authoritative server is located at the end of the DNS query, and the recursive resolver is present at the front part of the DNS query.

Recursive Domain Name System Resolver

It is a computer that checks the recursive requests and questions of a client. Recursive resolver takes some time to track the records of DNS. This server makes a chain of requests to track the history to reach the authoritative DNS server. These requests go to this nameserver for the requested record. Recursive resolvers do not need to create multiple requests every time for record tracking. Caching is a process that helps resolvers in short-circuiting essential requests.

Authoritative Domain Name System Server

It is present at the end of the DNS query. The authoritative server is responsible for holding the resource records of DNS. It is present in the bottom area of the DNS chain to respond to the records of queried resources. It allows the web browser that is responsible for creating requests to reach the IP address. The IP address gives access to a web resource or website. The authoritative server does not require to query other sources. This nameserver can satisfy the DNS queries with the help of its data.

When the query is added to instances for a subdomain like blog.cloudflare.com or foo.example.com, another new nameserver is added in series. This nameserver was added after the authoritative DNS server. It is responsible for storing subdomains.

A key difference is present between many services of Cloudflare and DNS. Many recursive resolvers maintain the installation of the data center of recursive DNS resolvers. These DNS resolvers are OpenDNS, Google DNS, and Comcast. They allow easy and quick queries by an optimized group of DNS-optimized computer systems. These servers are very different from the nameservers of Cloudflare.

What are the steps in a DNS lookup?

In the following paragraph, we have explained the step by step method of DNS working. DNS is defined as a domain name system. It is linked with a domain name that translates into the right IP address. The following steps will help you to understand this process of translating domain names. This process keeps traveling in a web browser. It works through the process of DNS lookup.

The ten steps in a DNS lookup

  1. When an internet user writes example.com in the search bar, the user's query starts traveling into the Internet. DNS recursive resolver receives this query.
  2. The DNS resolver sent the query to the DNS root name server.
  3. The DNS root name server responds back to the resolver. It gives the address of a top-level domain (TLD) DNS server. This top-level domain can be .net or .com. TLD is responsible for storing the domain information. When the user searches example.com, the request is sent towards the .com TLD. If the user types textbook .net, then it will refer towards.net TLD.
  4. As the user types example.com, then the resolver refers the request to .com TLD.
  5. The .com TLD server response with domain's name server address.
  6. After making the request, the resolver sends it to the nameserver of the domain.
  7. Nameserver returns the IP address for request.
  8. The resolver responds to the browser with the IP address of the request.
  9. HTTP request of IP address is then created by browser.
  10. The IP server returns the webpage to the browser's renders.

What is a DNS resolver?

It is present at the start of DNS lookup. It covers the initial steps of searching. The resolver responds to the user who researches anything in his search bar. DNS resolvers arrange a series of queries. The query or request then leads to a URL. This URL is translated into an IP address. There is a difference between the query of recursive DNS and the resolver of recursive DNS. The recursive DNS query is a request created in the DNS resolver and needs the solution of the query. The recursive DNS resolver is a computer system that accepts and accepts the query from a recursive DNS query.

What are the types of DNS queries?

There are three types of DNS queries given in below section;

Recursive question:

In a recursive query, the user of DNS needs the response. The DNS server is responsible for providing a response to the user. The response can be of two types. First is, the server records the resources of request. Secondly, the server shows an error if the resolver is unable to find the request record.

1. Iterative query:

In an iterative query, the user allows the server of DNS to provide the best answer to the query. If the server does not find a matching query, a referral will return to the DNS authoritative server. Then the client will use the referral address to make a new query. This process will keep going until the time comes over or an error occurs.

2. Non-recursive query

A non-recursive query occurs when the client Of the DNS resolver requests for the record. The record may have access because of its authority, or the history is in its cache. Usually, the DNS server cache the records of DNS to stop the extra consumption of bandwidth.

What is DNS Caching? Where does DNS caching occur?

Caching is used to store data for some time. Cache stores data in a place that improves the reliability and performance of the data request. It keeps data near the requesting client so that it can be resolved quickly. It also avoids extra queries. Caching can store data in different locations. Each location stores the records for a specific time that is known as time-to-live (TTL).

Browser DNS caching

Advanced web browsers are created by default for caching of DNS records. The cache data for the calculated time. A limited range of time enables the browser to face a few steps of processing to check the cache. It also helps the browser to make a correct query to an IP address.

Operating system level DNS caching.

It is the local and last stop that comes before a query leaves the machine. Stub resolver is designed in the operating system to handle the query. Thus, stub resolver is also commonly called DNS design. When a request is submitted in the stub resolver, the resolver checks first its cache and its ability if it has a record or not. If its cache has no record, then it sends the request outside to the local network.



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