DNS stands for Domain Name Server and one of the easyiest approaches to load balancing is via DNS – hence DNS Load Balancing.
With DNS it is possible to allow multiple IP addresses to be associated with a single server name or hostname. So you might have 10 servers at the backend and one server at the front. The IP address of the frontend server is associated with the IP addresses of the backend servers.
When a request is made to the frontend server it load balances the requests across the backend servers in a round robin or one at a time basis.
This is easy to set up and configure however it’s simplicity is also its achilles heel. Namely:
* you can only use a round robin approach and not other more sophisticated approaches like least connections
* it cannot monitor servers to see if they are still up and running
* all requests are on a round robin basis do sticky sessions are not supported
* it is not possible to ensure an even load distribution across all of the backend servers
Nonetheless it is a simple approach that is easy to set up.
Here is a slightly oddball (but good) video that outlines the basics of DNS:
And here is a link to the wikipaedia explantion: http://en.wikipedia.org/wiki/Round_robin_DNS
