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Back To Basics: What Is DNS, And How Does It Work?

DNS – or, the Domain Name System – is one of the least known yet most important building blocks of the internet. DNS functions as the backbone of the internet, ensuring that the domain name an internet user types into their computer or smart device takes them to a website. Technically speaking, DNS resolves human-readable hostnames like www.dyn.com into machine-readable IP addresses like 204.13.248.115. DNS also provides other critical information about domains to systems such as mail services.

So why is DNS so critical to the internet and how does it work?

Many have likened DNS to the phone book of the internet – but it can also be compared to our sprawling local and national highway grid; high performing managed DNS ensures not only that traffic moves as fast and as efficiently as possible, but also that it always reaches its destination. Best-in-class DNS makes the internet faster for companies doing business online, but it is also essential to end-users who expect near instant access to websites and apps and do not look kindly on timed out webpages.

DNS is so ingrained in the mechanism of how the internet works that without it, the internet would not have scaled to where it is today.

How does DNS work?

Let’s get technical.

When any internet user visits a domain such as dyn.com, your computer or smart device follows a number of steps that turn the human-readable web address into a machine-readable IP address. Every time a domain name is typed into a browser, an email is sent or music or content is streamed from Netflix or Pandora this same action occurs – it is the core function of DNS.

Step 1: Information Request

The first step in the DNS query process occurs when your computer or smart device is asked to resolve a hostname (visiting dyn.com). Your computer will automatically refer to its local DNS cache, which stores information that your computer has recently retrieved.

If your computer doesn’t already know the answer, it needs to perform a DNS query to find out.

Step 2: Refer to recursive DNS servers

Recursive DNS nameservers are responsible for providing the proper IP address of the intended domain name to the requesting host. If the DNS information your computer or smart device is not stored locally, your computer queries (contacts) your internet service provider’s (ISP) recursive DNS servers. Recursive servers have their own caches, so the process may ends here and the information is returned to the user.

Step 3: Ask the root nameservers

In the event the recursive servers don’t have the answer to the query, they contact the root nameservers. A nameserver is a computer that answers questions about domain names, such as IP addresses. There are thirteen root nameservers around the world that serve as the international DNS switchboard for the internet (Dyn recently partnered with the Internet Systems Consortium to Host one of these nameservers, F-Root, and has a long track record of helping improve global internet performance).

Step 4: Ask the TLD nameservers

The root nameservers will look at the first part of our request, reading from right to left — dyn.com — and direct our query to the Top-Level Domain (TLD) nameservers for .com. Every TLD – .com, .org, .net, .us and others –  have their own set of nameservers. While these servers don’t have the information we need, they refer us directly to the servers that have the information necessary to complete the query.

Step 5: Ask the authoritative DNS servers

The TLD nameservers review the next part of our request — dyn.com — and direct our query to the nameservers responsible for this specific domain. Authoritative nameservers are responsible for knowing all the information about a specific domain (stored in DNS records).

Step 6: Retrieve the record

The recursive server retrieves the specified record for dyn.com from the authoritative nameservers and stores the record in its local cache; at this point, anyone who may request the host record for dyn.com will be able to do so as the recursive servers will already have the answer and will not need to go through the lookup process again. Every record has a time-to-live – or TTL – value, which is like an expiration date. If too much time has elapsed the recursive server will need to ask for a new copy of the record to ensure the information is not out-of-date or otherwise inaccurate.

Step 7: Receive the answer

After this process, the recursive server returns the record back to your computer or smart device – this all takes milliseconds, though it’s a multi-step process. Your computer stores the record in its cache, reads the IP address from the record, then passes this information to your browser. The browser then opens a connection to the webserver and receives the website. Ta-da!!

Conclusion

The importance of DNS to any organization doing business online cannot be understated. Well-functioning DNS will limit or eliminate latencies (the time it takes a website to load) and dramatically increase internet performance – both for your business and for your customers, partners and end-users.  

Click here to see our own Andrew Sullivan, Evangelist, explain DNS in detail via video.

And for more information about Dyn’s Managed DNS offerings, visit http://dyn.com/managed-dns/.


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Whois: Brendan Mangus

Brendan Mangus brings more than 15 years of marketing communications experience to his post as Public Relations Manager at Dyn. Throughout his career he has served as an advisor to C-Suite executives for a range of companies, from startups to Fortune 500 multinationals and in a variety of B2B and B2C industries including plastics and chemicals, building and construction and consumer and Enterprise technology.