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Yesterday was a great day for DNS with Cisco buying recursive DNS provider OpenDNS. I received many emails from friends and colleagues relaying the news to me and they were almost as excited as I was. They all know I have built my career around providing DNS services to companies across the globe and this news was just good for DNS in general.

In light of all this attention to DNS yesterday, I saw a common theme amongst all the emails – most everyone thinks there is just one type of DNS and lump us all into the same category. That’s not the case and here’s why:

There are two main types of DNS servers – Recursive and Authoritative. OpenDNS acts as a RECURSIVE service, allows computers all over the world to ask OpenDNS where a domain name resides (on what IP address). In order to truly understand what’s happening and why there are two main types of DNS servers, we have to go back to examine what happens when you browse to “google.com” on your laptop, tablet or smartphone or open a cloud-based app.

When you lookup a website in your browser or open an app on your smartphone, there is a ton of DNS activity that goes on to make all the magic happen. There are requests and responses for websites, images, video,etc. A Recursive server does most of the first answering, and they ask other authoritative DNS servers for the answers. Those servers respond back to your browser. (There is more that goes on but this is the simplistic version)

Recursive DNS
Example: OpenDNS / Google DNS / Your ISP’s DNS

These servers are first line responders to your web browser and Apps when they request a domain name or internet resource. If the name is not locally cached or known on the Recursive DNS server, then is will ask the Authoritative DNS server for the answer and respond back to the asking client/browser/app.

This recursive DNS server is typically housed at your ISP since it’s very close to you, and this server simply is a “fetching machine” where it fetches names from AUTHORITATIVE SERVERS to then hand back to your browser with the proper IP address. OpenDNS is a recursive DNS provider that allows you as a company or individual to use their service to help speed up your browsing and protect you from malicious names, or even add parental controls blocking any domain name with the word “sex” in it for example.

CloudfloorDNS is an authoritative DNS provider, where we take your company’s database of names and IP addresses and we answer for them with speed and reliability. We can also do some fancy things with DNS such as Failover and GEO Load Balancing, but that’s another article….

Authoritative DNS
Example: CloudfloorDNS Managed DNS

CloudfloorDNS is the authority for client hosted second level domains (example.com). If a domain name is not known on a Recursive DNS server such as OpenDNS then the OpenDNS will ask the CloudfloorDNS servers for the Authoritative answer and respond back to the client with the correct answer.

There is a very organized, hierarchical structure to the DNS system. This goes all the way from the sub-domains (yourname.example.com) to the second-level domain names (example.com) to the top level domains (.com, .biz, etc), then the root servers (The all knowing wizards of the internet) which are at the highest level in the DNS tree.

I hope this helped you understand the differences between the types of DNS servers you may come across in your internet adventures. Probably the most important thing to take away is that DNS is a critical piece of infrastructure to your organization, no matter how big or how small. Next to having your domain name actually registered, DNS is the next most important technology in the chain to completing any web transaction, download, or web page view. DNS is everywhere and unfortunately nobody thinks too much about it until it doesn’t work!