The Concept and the Evolution
Round Robin DNS (RRDNS) is a technique used for load balancing traffic on any site or FQDN with the need of actual load balancing hardware or extra equipment. It involves use of DNS servers to distribute traffic to different physical servers which may be configured to serve web, mail or any other type of traffic. This technique is mostly used on large networks where the traffic level is not manageable by a single machine. Round Robin DNS largely depends on the TTL (Time to Live) values set for the DNS records.
Each DNS record has multiple IP addresses assigned to it . Each time a DNS request is made for the record one of the Ips is returned as the Result in a Round Robin fashion. This allows distribution of traffic amongst the multiple Ips. The lower the TTL, the faster these IP addresses are rotated. The disadvantage of using a lower TTL is that it increases the load on the DNS server. RRDNS is very useful for sites which have very heavy traffic and have a geographically dispersed audience as well as geographically dispersed web servers. With the help of RRDNS and another advanced technique called as GeoLocation, these sites are able to redirect their audience from particular countries/continents to their local sites.
Round Robin DNS is also used for services like mails , ftp and even IIRC. Most corporate domains have multiple mail servers configured in round robin mode to handle the huge amount of mail traffic they get. We use Round Robin DNS as a core concept with our servers. Being a service provider which offers only clusters and custom high traffic hosting setups, round robin dns is an integral part our services. Through this site we will be having a contact point for our existing client base as we will be using it to share and gather knowledge about this amazing concept. There will be a lot of how to's and other material posted on this site soon. If you are interested in contributing anything related to round robin DNS on our site, you are more than welcome to do so. RrDNS.com is now more of an informative site now that we have moved over all our commercial services to RrDNSHosting.com. You can browse through our technical articles and how to's on this site .You can use use the Contact Us form on the site to get in touch with us. We would be more than glad to give you full credit your work without any modifications from our end :)
Modern day service providers like Cloudflare use RRDNS on a large scale for redundancy.