DAZN Engineering
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DAZN Engineering

DNS for Noobs

We are going to be looking at DNS, especially for anyone new to DNS or is unsure about it. We will look at what DNS is, how a domain name is structured, where the DNS goes to get the information and the different types of records.

What is a DNS?
DNS or Domain Name System, are a way for computers to translate human readable domain names (e.g., www.dazn.com) into an internet protocol (IP) address (e.g. 65.8.178.106) via a process called resolution.

If you have used the internet, then you have used DNS (even if you did not realise!)

What is a Domain Name?
Remembering a bunch of numbers can be difficult, so domain names were created in order to help users navigate around the world wide web. A domain name is made up of letters and dots.

So, how does DNS work?

The primary job of a DNS server is to resolve a domain name into an IP address. It sounds easy, but if you think about it, there are billions of IP addresses which in turn means there are billions of requests; That is without considering all of the domains being added or changed every day too!
The concept of DNS is a little like using a phone book. You need to find a service, so you go and look up the telephone number for that service. In DNS terms, your service is the web address, and the telephone number is the IP address.

Let’s break it down:
1) A user opens their web browser (chrome, Firefox etc) and types in a web address, e.g. www.dazn.com, the computer and browser checks to see if you have visited the address before and if one of them has the related IP address stored there.
2) If the web address is not in the local cache, the browser asks the computer to use its operating systems DNS service to go and find the required IP and translate it into a web address. This is a process known as DNS name resolution. If the DNS service has the domain name and IP address in its own database, it can resolve the name itself, if it does not have the domain name and IP address, it will contact another DNS server on the internet.
3) Once an IP address is found for the web address, it gets mapped.
4) The DNS server is then able to cache the web address with mapped IP address for a time, in case it is needed again soon.
5) The computer can now display the content from the web address.

Where does a DNS Server get the information?

So, we know a DNS server retrieves the information to send back, but where does it look to get this information? DNS is made up of nameservers. The easiest way to think about this, is in the form of a hierarchy. The DNS server sends a referral to the root nameservers which store the locations of the Top-Level Domain (TLD e.g., a .com, .co.uk etc). Each TLD uses nameserver records to direct the traffic to the correct authority for the records. This is usually where the domain was bought and is hosted (e.g., GoDaddy, AWS) These records then contain further information about that domain.

What are the different types of records?

NS record (or name server record) is used by top level domain servers to direct traffic to the content DNS server that contains the relevant DNS records.

A Record (or address record) is the fundamental type of DNS record used by the computer to translate the name of the domain to an IP address.

CNAME (canonical name) can be used to resolve one domain to another. E.g. - you may have a mobile website that is used when users browse to your domain name on their mobile devices. It is basically just a way of mapping one domain to another.

MX record (mail exchanger) points email to a specific mail server. It works in a similar way using the DNS. It will look up the nameservers for the domain and will query those nameservers for the MX records to find out where to deliver the messages.

TTL (time to live) is the length in seconds that a DNS record is cached either on the resolving server or the user’s local computer. The lower the ttl, the faster the DNS records take to propagate through the internet.

Phew, is that all?

We have learned that a web address has various parts, and the DNS uses those parts in order to find out where to look to translate the address into an IP.
We have looked at how the DNS server routes its requests, and also, the several types of records that are used.
DNS has come a long way from the early 1980’s to what we know and see today. It is not a static concept and has rolled out security features and improvements over the years. There continues to be new propositions on the best way to manage DNS.
Thankfully, DNS has made everyone’s life easier to find things on the internet — in the milliseconds it takes to load a web page, the DNS is working behind the scenes running the requests faster!

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