The following is a crash course on the Domain Name System, or DNS, which will help answer some of those questions. Its intended for those unfamiliar with the concepts, and does not contain any code.

What is DNS?

When you type www.google.com into your browser, your computer is connecting to another computer via the internet, in this case a Google server, and downloading the Google website for you to view. But of the millions of computers connected to the internet how did your computer know which one is Google’s? This is where the Domain Name System comes into play.

Computers connected to the internet identify themselves by an IP address, which consists of 4 numbers ranging from 0 to 255, called octects, joined by periods. For example, the server which hosts illuminatikarate.com’s IP address is 67.19.177.157. Your computer also has an IP address, which you can find by going to this website. In fact, you could use this address: http://64.233.187.99/ instead of Google.com if you wanted.

So at its most basic, DNS is a list which matches domain names like google.com and illuminatikarate.com to IP addresses like 64.233.187.99 and 67.19.177.157. Furthermore, this list is collaborative, and the owner of each domain is responsible for contributing their entry to the list.

In order for your website to be reachable, you need to maintain your DNS entry which links your domain to its server’s IP address. This is done through a nameserver (usually two nameservers are specified for each domain, which is why you most often hear them referred to in plural). Your web host will let you use their nameservers so you don’t have to maintain your own.

Although there are over 25 types of DNS record types, and most are fairly esoteric, there are a few which you should be familiar with.

Nameserver Record (NS Record)

Nameserver records, or NS Records, are tell the requesting computer where to look for your DNS information. Its essentially passing the request down the chain. If you host with Illuminati Karate, these will be ns1.illkd.com and ns2.illkd.com.

Note: An NS record will direct all traffic types (e.g. web, email, and FTP) to the same address. If you want to send different traffic types to different servers, you’ll need to use A and MX records instead, which are explained below.

Address Record (A Record)

An “A record” maps a domain or subdomain’s web traffic to an IP address, while leaving its email alone. Using A records you can route
www.mysite.com and test.mysite.com to completely different servers.

Mail Exchange Record (MX Record)

The MX record routes email while leaving other traffic alone, and is commonly used when hosting email with a 3rd party, such as a hosted Exchange server or Google Apps.

Canonical name record – CNAME Record

A CNAME record is used to redirect the request to another domain name. For example, if you moved your site from www.site1.com to www.site2.com you could use a CNAME record to send anyone going to site1.com to site2.com.

Note: Using CNAME records for domain redirection isn’t recommended for SEO purposes, although the reasoning is beyond the scope of this article. If you find yourself in such a position, drop us a line and we’ll set up an SEO consultation.

Conclusion

Although its concept is simple, the DNS is quite powerful. For example, a large website like Google doesn’t reside on a single computer, or even in a single location. It takes hundreds of thousands of computers to handle the 235 million queries a day performed on Google, but we all want to interact with Google.com. DNS allows us to do so, by providing this abstraction while allowing the website to perform its complex routing.