DNS clients use libraries called resolvers that perform DNS queries to servers on behalf of the client. Keep in mind throughout this discussion that a DNS server can also be a client to another server.
Computers running under Microsoft® Windows NT® Workstation or Microsoft® Windows NT® Server version 4.0 use DNS name resolution when a name query contains a name that contains a period or is greater than 15 bytes in length. Computers running Windows 2000 always try DNS name resolution. For more information about DNS and NetBIOS name resolution, see "TCP/IP Troubleshooting" and "Windows 2000 DNS" in this book.
DNS clients can make two types of queries: recursive and iterative.