Domain Name System based load balancing, popularly known as DNS load balancing is a practice of boosting speed and reliability by distributing the website traffic across multiple servers.  In the absence of load balancing, websites would fail to handle or manage massive amounts of traffic effectively.  Let us take a closer look at what dns load balancing is. 

What is DNS Load Balancing? 

Websites need DNS based load balancing to manage massive amounts of traffic as DNS load balancing distributes the incoming traffic to various servers which makes sure that you experience a smooth and seamless experience while exploring the website.  

DNS acts like a directory for businesses (websites). Just like a phone book tells you the phone numbers for different businesses, DNS tells you the IP addresses for different websites. And IP addresses is a unique identifier that computers use to find each other on the internet. 

During the DNS resolution process, the user’s server contacts a DNS server to obtain the correct numerical IP address of the destination website. To prevent failures, manage high traffic, and provide a seamless user experience, most domains use multiple DNS servers. A DNS load balancer efficiently selects which IP addresses to share in response to DNS queries using various methods and tools. 

DNS has also been proven to play a pivotal role in disaster recovery. If a data center fails or goes offline, the DNS can direct traffic to another data center, ensuring that the service continues without interruption.  

Advantages of DNS Load Balancing? 

There are several advantages of using the Domain Name System (DNS), some of them are mentioned below:  

  • Firstly, the DNS-based load balancing system makes the performance even better by making sure that a single server is never overwhelmed, which further leads to improved response time and enhanced user experience.  
  • Another reason DNS-based load balancing is reliable and effective is that the DNS load balancing system can reroute the traffic to other functioning servers, which reduces downtime and further enhances the user experience. 
  • Its geographical distribution is known to reduce latency and improve load times by directing the users to the nearest server. 
  • One of the most prominent advantages of using DNS-based load balancing systems is that they are cost-effective as they do not require any specialized hardware to operate.  
  • Lastly, it also enhances security by muddling up the IP addresses, which makes it tough for attackers to target specific users.  

How does DNS Balancing work? 

The process of DNS load balancing starts with a DNS query which is sent by a client who is seeking to resolve a domain name. Then, the DNS server which holds records of the domain, responds with various IP addresses corresponding to different servers which are hosting the service. At last, the client then can choose one of these IP addresses to send its request.  

As discussed earlier in the blog, there are several techniques which are used to balance the load and some of which are mentioned below:  

  • Round-Robin DNS: This is one of the simplest techniques used to balance the load. In this technique, the DNS server shuffles the order of IP addresses with each query, which then distributes the traffic evenly amongst the servers.  
  • Weighted Round-Robin: It is one of the most advanced methods to balance the load where the servers are assigned weights which are based on the capacity of each server and the geographical DNS. It then directs traffic to the nearest server to minimize the latency. 
  • Monitoring server health is also one of the ways to balance the load because a DNS server can, at times, stop distributing its IP address if a server is unavailable. So, to make sure that the user experience is enhanced, the clients should be directed to operational servers. 

How to use DNS as a Load Balancer? 

If you want to use DNS as a load balancer, then you will have to configure multiple A or AAAA records for the same domain and make sure that each one of them points to different server IPs. DNS round-robin is one of the most prominent techniques used to balance load.  

The only disadvantage of this technique is that advanced features like health checks are absent, but at the same time, it is simple to use and cost-effective for basic load distribution.  

What are other types of DNS-based load balancing? 

As mentioned earlier, Round-Robin DNS is one of the various DNS load balancing methods. In addition to Round-Robin, there are several other methods, each offering unique advantages depending on the use case and desired outcomes. 

GeoDNS (Geographical DNS):

Users are directed to the nearest server to their geographical location. Further, GeoDNS reduces the latency which in-turn improves the load times. GeoDNS does this by responding to DNS queries with IP addresses of servers which are located near the user. This method has proven to be useful for global applications wherein the server proximity plays a pivotal role. 

Weighted Round Robin:

Weighted Round-Robin is different to the Round-Robin method. In Weighted Round-Robin, the server is assigned different weights based on their capacity or current load. This method enables better utilization of the server resources and at the same time it is also useful in environments with heterogeneous server capabilities.  

Latency-based DNS Load Balancing:

The servers are selected based on the current network latency to the user. Furthermore, this method also ensures faster response times as the DNS queries are directed to the server which possesses the lowest latency.  

 Failover DNS:

This method enhances the user experience by monitoring the health of the servers which are at the backend and then it responds with IP addresses of servers that are currently operational. If a server fails, then its IP is removed from the DNS responses, ensuring high availability and reliability. This method can be used where the critical applications require continuous uptime.  

Proximity-based DNS:

Like GeoDNS but often more granular, this method uses network topology data rather than just geographical data to determine the closest server. This approach can account for network congestion and routing efficiency, leading to better performance. 

Anycast DNS:

DNS queries are routed to the nearest server using the same IP address as before. Anycast offers benefits such as redundancy and load distribution as its underlying network routes and mechanisms to direct traffic. This method is usually used to mitigate DDoS and improve resilience.   

The DNS load balancer enhances the user experience by using various methods like Weighted Round-Robin, GeoDNS, Anycast DNS, etc. By using these techniques, DNS load balancing enhances the website’s performance and reliability by distributing the traffic across various servers.  

Additionally, it has also been proven to enhance the user experience by reducing latency and ensuring high availability which further makes it indispensable for the modern IT infrastructure.