Microsoft DNS server supports a process referred to as round-robin, which balances the number of clients connecting to Internet sites supported by multiple servers. Round-robin is specified by RFC 1794. To make use of round-robin, you use an alias such as the generalized server name www.
To understand how round-robin works, consider the following example. Suppose a user types the URL http:\\www.microsoft.com into an Internet browser. Doing so causes a name resolution query for www.microsoft.com to be sent to a DNS name server. The DNS name server returns a list of name-to-IP address mappings for each CNAME resource record that maps a host name to the alias www.microsoft.com.
The next time the DNS server receives a name resolution query for www.microsoft.com, the order of the list CNAME records is changed in a round-robin fashion. The address mapping that was first in the previous list is last in the new list. Because the process on the client computer generally uses the first name-to-IP address mapping in the list, the client connects to a server different from the server connected to on the previous request. In this manner, client connections to the Internet site are distributed among the supporting servers.
To enable round-robin when you use multiple servers to support a Web, FTP, or Gopher site, create CNAME records for each server as described in the preceding section, "Using An Alias."