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Recursive DNS: How Does It Work?

By

Product Manager, Traffic Management

So what is Recursive DNS and how does it compare to Dyn Standard DNS?

The Short Answer

Recursive DNS is essentially the opposite of Dyn Standard DNS which is an authoritative DNS service that allows others to find your domain while Recursive DNS allows you to resolve other people’s domains.

The Longer Answer

Recursive DNS provides recursive DNS. Yes, that’s recursive (something which repeats or refers back to itself) and confusing. In order to make a distinction between the service we provide and the general concept of recursive DNS, here’s an explanation.

To better illustrate how recursive DNS works, let’s imagine you are sitting at a computer in your study at home. You’re connected to the Internet by a cable connection and you are surfing the web looking for widgets. You have no idea where to find widgets, so you open your web browser and type in http://www.google.com.

This is when recursive DNS kicks in. Your web browser looks to see if it knows where to find the machine “www.google.com”. If it doesn’t have this info stored in its own cache, it will ask your operating system (OS) if it knows where to find this host. If your OS doesn’t have this in its cache, your OS will perform a DNS query to find that info. That query will go to the DNS servers provided by your ISP and these servers are configured to provide recursive DNS.

To simplify things, the ISPs nameserver will send a query to the “root” name servers to find out who is responsible for the .COM domain (i.e. which name servers are authoritative for the .COM domain). Once it has this info, it will send a DNS query to those nameservers asking them who is responsible for the google.com domain and then a final query to those name servers asking for the address of www.google.com.

Those servers which answer for google.com and resolve www.google.com to an IP address? Those are authoritative DNS servers (like our Dyn Standard DNS except we don’t provide DNS for Google).

Now this is where our Recursive DNS service comes into play.

Sometimes, an ISP’s recursive DNS servers get overloaded and the queries you send to them can start timing out. When this happens, you can’t find www.google.com and so you can’t search for widgets.

Why are your ISP’s recursive DNS servers overloaded? It could be any number of reasons, but it happens. In any case, what we provide is an alternative set of servers that you can use in place of your ISP provided nameservers. That’s our Recursive DNS service.

If you need something better than your ISP’s recursive DNS servers, try our free Internet Guide which is pretty awesome.

Chris Gonyea is Product Manager, Traffic Management at Dyn, a cloud-based Internet Performance company that helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Follow on Twitter (@ChrisGonyea and @Dyn).