What is the purpose of Round-Robin DNS?
How many times have you heard the phrase “simpler is better”? Well, maybe that inspired the creation of Round-Robin DNS.
The purpose of Round-Robin DNS is to execute DNS load balancing. It’s not hardware but a software solution created to operate on DNS nameservers.
What is load balancing?
Load balancing is a technique for optimizing networks’ performance. It works by defining an algorithm to distribute the traffic among multiple servers. This is a very useful practice that provides redundancy, faster and better performance, higher uptime, and quicker load time. The gain is worth it! If a server is not available, you can be relaxed and sure that others can handle the traffic. It will prevent stressed servers (bottlenecks) by reducing their load and directing it to alternative ones.
How does Round-Robin DNS work?
Let’s think you enable Round-Robin DNS for your domain name. Different A records will be stored. Every one of them will have a different IP address but the same domain name. Whenever there’s a request for this DNS record, an answer (IP address) will be delivered. Once it’s no longer in use, it will get back to the end of the line waiting for its turn to be used again. This will create a rotation cycle for your multiple IP addresses.
Here you can visualize easier the purpose of Round-Robin DNS. Think you have your domain’s content hosted on several redundant systems geographically spreaded. Enabling Round-Robin DNS, you give the authoritative nameserver the power to use the rotation cycle to answer requests with different IP addresses. And by doing this, the traffic load will be balanced.
Of course, this task could be executed through other load balance methods. There are many alternatives, even more, sophisticated than Round-Robin DNS, but they could involve extra steps and higher cost. GeoDNS, for instance. It will check the IP address of the DNS client to compare it with its table of IPs. Then it will redirect to the server it thinks is better for the client. In this case, you will need a GeoDNS with updated tables. That definitely takes extra work and money.
Pros of Round-Robin DNS.
- It’s a really affordable solution.
- It’s easy to be implemented.
- It has proven its capability to manage DNS traffic by redirecting it to different servers.
- Traffic optimization through load balancing improves the performance of your domain directly.
Cons of Round-Robin DNS.
- It’s focused on the rotation of the IPs, but it doesn’t have a way to check if the servers are working properly. It can send traffic to a troubled server that won’t answer your clients as expected. This can already be overcome through additional methods for detecting unresponsive servers. Once detected, it or they can be taken out from the rotation.
- While working, it doesn’t consider important factors like geographical distance, transaction time, server, or network load. This is a disadvantage when comparing it with other load balancing methods that can check such factors.
- It can’t manage the combination of DNS caching and client caching. Therefore It does not always equally manage the load. If a client’s DNS request for loading a domain reaches a recursive server facing high traffic, it will cache the domain’s IP. That can mean more traffic sent to that IP.
Round-Robin DNS is a simple solution with a really big purpose! You have the chance to complement it with other technologies to improve its possibilities! If it’s better or not, it’s a decision that domains’ owners should take based on the particular needs they have.