A DNS query in which a name server contacts a second name server to perform a name lookup.
In a typical Internet name lookup (for example, www.alpine.expedia.com), a resolver sends a recursive query to a locally accessible name server such as a name server maintained by your local Internet service provider (ISP).
If the local name server cannot resolve the name because it is outside of its zone of authority and it is configured as a forwarder, the server performs an iterative query to a root name server, which responds with the IP address of a name server whose zone of authority includes the desired top-level domain (.com).
The local name server then performs an iterative query with this top-level name server, which responds with the IP address of a second-level name server whose zone of authority includes the desired second-level domain (expedia.com).
The local name server contacts this second-level name server and resolves the fully qualified domain name (FQDN) into its IP address or returns an error if the query cannot be resolved.