Ok, so you are checking how to improve your DNS infrastructure. Great! There are different routing methods that you can use for your domain resolution. Now we will compare Anycast DNS and GeoDNS and see what their advantages and disadvantages are.
What is Anycast DNS?
Anycast DNS is a simple routing method with a single IP address for all of the name servers. The servers are located in different international locations. That way, a client’s query will search for that single IP address, no matter from where in the world he or she connects, and it will reach the closest server.
What is GeoDNS?
GeoDNS uses multiple name servers, strategically located around the globe. The big difference is that the servers have the same IP address per region. When a client connects, the name server will check its IP address, and the client will be redirected to the local server for its region.
Anycast DNS vs. GeoDNS
The way it works
In the case of Anycast DNS, you have many name servers that will answer with the same IP address, located at different points of presence (PoP). A query from a DNS client will travel from hop to hop, and it will be answered from the first authoritative name server it finds. This makes it very fast to respond, but it is not intelligent in any way.
The easiest way to think about Anycast DNS is that there is a single IP address and multiple PoP.
The GeoDNS will first check the IP address of the DNS client by comparing it to the database it has with IP and regions. Then, based on it, it will redirect the DNS client to the closest server, based on its region.
The easiest way to think about GeoDNS is that it has a single IP address per region but multiple regions (each with its own IP address).
Anycast is a relatively economic technology that many Managed DNS providers offer. You can find it inside almost every Managed DNS plan. Usually, there are no additional charges for Anycast DNS.
GeoDNS is more sophisticated, so it does not come for free. Usually, the Managed DNS providers have additional plans that are focused on GeoDNS. It is more expensive than the Anycast.
Ease of use
Both Anycast DNS and GeoDNS are easy to set up if you are using a Managed DNS provider. Depending on the software that the provider offers, or in case you have your own servers, you might need to search for databases with IP addresses for the GeoDNS. So, there is a chance that GeoDNS is a bit more difficult to set up.
Thanks to the way GeoDNS works, it can be used to deliver content based on the clients’ IP addresses. Like Netflix, the clients in London can see local content, which is different from the content for the US clients. Anycast can’t do that.
While both can provide redundancy, here, Anycast wins. If one name server is down, the query will just continue to travel until it reaches another Anycast server from the network. The client will notice a slight delay, but nothing more. In the case of GeoDNS, if a particular server that is responsible for the answer for a region is down, and there is no another in the same region, the clients could experience longer downtime.
Both services can be used for optimizing DNS traffic and can speed up your domain resolution. Now you know their differences.