Round robin is a method of distributing multiple sources to one of the many devices or connections. For example, a company may have multiple servers that are identical to each other. When the first user attempts to access information from the server they may be referred to "SERVER_1"; however, the next user is directed to "SERVER_2" regardless of its load.
原文：http://www.cnblogs.com/kex1n/p/5730305.html