Round robin DNS is a method of managing server congestion by distributing connection loads across multiple servers (containing identical content). Round robin works on a rotating basis in that one server IP address is handed out, then moves to the back of the list; the next server IP address is handed out, then it moves to the end of the list; and so on, depending on the number of servers being used. This works in a looping fashion.
Let's say a company has one domain name and three identical home pages residing on three servers with three different IP addresses. When one user accesses the home page it will be sent to the first IP address. The second user who accesses the home page will be sent to the next IP address, and the third user will be sent to the third IP address. In each case, once the IP address is given out, it goes to the end of the list. The fourth user, therefore, will be sent to the first IP address and so forth.
Round robin is different than load balancing. Load balancing distributes connection loads across multiple servers, giving preference to those servers with the least amount of congestion. In round robin's case, server distribution remains on a rigid one IP address to one user rotating basis.
As an example, let us assume that we, at MyServer.org, have three (3) web servers:
First visitor to www.MyServer.org goes to 209.219.51.101
Second visitor to www.MyServer.org goes to 68.15.187.28
Third visitor to www.MyServer.org goes to 209.219.51.103
So, 1/3 of the web requests going to www.myserver.org will be directed to 209.219.51.101.