Posted on April 14, 2014

Upgrade to Anycast DNS Infrastructure

We’ve made some changes to the way our DNS structure works, moving away from the Unicast DNS to an Anycast DNS. By changing to an Anycast DNS, the biggest benefit is speed; you no longer have to always hop to a single destination. But another benefit is that a network becomes much more resilient and can also handle DDoS attacks. So it is a no brainer for us to now offer this free with all of our Shared Hosting, Enterprise Hosting, Reseller Hosting, and any VPS and Dedicated Hosting clients that are using our DNS.

Without getting too technical, let’s discuss how querying a DNS in both a Unicast and Anycast DNS environment.

In either case, when someone visits your site after typing in the domain name, let’s say for example www.fullhost.com, your web browser/operating system starts a search for the IP address associated with fullhost.com which is known as a DNS request. It begins to search out the IP address for the domain. If the request hasn’t been stored in your cache, it will first check with the resolving name server (usually your ISP) to see if that has been requested by someone else and is in their cache. If this hasn’t been cached there either, it will now then look at the authoritative name server, which is the one associated with the web host, us. Each step takes a little bit longer, so if it is stored in your cache or the resolving name server’s cache, it will be served a bit quicker than going to the authoritative name server level.

The difference between how a Unicast and AnyCast DNS works is at the authoritative name server level.

Unicast DNS

Unicast
Unicast

Your browser is now trying to locate the authoritative name server associated for the domain by means of the IP address pointing to the node that it is being served from, which in a Unicast environment cannot be shared over multiple locations. An IP address can only be served from one node in one location, unique to where it is. Your domain needs to have a number of authoritative name servers for the domain registry, and each name server (ns1,ns2,ns3,etc) has an IP address associated with each of them. For proper redundancy, these name servers should be placed strategically around the world, but unfortunately when a DNS request goes to the authoritative level, it doesn’t find the one closest to you, but will query any of them.

So once the DNS request determines which name server (ns1,ns2,ns3,etc) to use and the IP address for it, it will begin the search out for the best and fastest path. Routers are very critical in finding the shortest path to this IP address in land of the interwebs. They keep a directory within themselves of where the IP is, and the shortest path to get to it. So as your DNS request goes to the router, it finds it, and shoots your request in the right direction. Each router brings you closer and closer to the IP address.

You may have heard the terminology trace route; well that essentially is what has been described above. It means the number of hops to the destination, which are turns at each router along the way. In theory, the less hops means it is closer to you. So once your little digital fellow runs the course, it hits the destination and sends back what you’ve requested. Voila, you now see our cool site on your screen.

Anycast DNS

Anycast
Anycast

So where a Unicast DNS only allows that one IP address is for one node in one location, an Anycast DNS allows that IP address to be shared in multiple locations. So each of the name servers (ns1,ns2,ns3,etc) will all have the same IP. What’s even cooler is that each of the name servers will be hosted in multiple locations (in our case 5 locations to with a 6th in the works). So when the DNS query goes to the domain registry to find the name servers, no matter which name server it chooses to query, the router will find one of the 5 locations around the world that the name server is on, which is closest to where the request is coming from.

So where are the DNS servers located you ask? They are in Toronto, Vancouver, Los Angeles, Dallas, London UK, and soon Hong Kong.

Comments

  • Hey guys,

    Great article. Two things:

    There’a a typo in the final paragraph above Anycast DNS. The second sentence starts with ‘is means’ instead of ‘it means’.

    I’m interested in the technical side of how the AnyCast DNS is being used: does this mean that you are know mirroring sites across the network’s nodes; or are you using MongoDB and/or a combination of Hadoop or something similar?

    Thanks,
    Avi

    • Hi Avi,

      DNS in either a Unicast or AnyCast environment does not in any way mean that the sites are being mirrored in multiple locations, and only is for the DNS itself. How this helps is that when a DNS request is checking our authoritative name servers, it will serve that request from any one of the 5 locations we are using, thus speeding up the process of finding the IP address associated with the domain and then pointing that request directly to our server in Canada.

      In a Unicast enviornment, each DNS request will point to only one server location. As it does not look for the name server closest to your location, it choose one at random, this can thus increase time to process the request itself.

      Hope that clarifies things, and thanks for pointing out the grammatical error, it has been tracked and corrected.

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