Domain Name Protocol

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The Domain Name Protocol (DOMAIN) allows a host in a domain to act as a name server for other hosts within the domain.

DOMAIN uses UDP or TCP as its underlying protocol and allows a local network to assign host names within its domain independently from other domains. Normally, the DOMAIN protocol uses UDP. However, if the UDP response is truncated, TCP can be used. The DOMAIN protocol in TCP/IP supports both.

In the DOMAIN hierarchical naming system, local resolver routines can resolve Internet names and addresses using a local name resolution database maintained by the named daemon. If the name requested by the host is not in the local database, the resolver routine queries a remote DOMAIN name server. In either case, if the name resolution information is unavailable, the resolver routines attempt to use the /etc/hosts file for name resolution.

Note: TCP/IP configures local resolver routines for the DOMAIN protocol if the local file /etc/resolv.conf exists. If this file does not exist, the TCP/IP configures the local resolver routines to use the /etc/hosts database.

TCP/IP implements the DOMAIN protocol in the named daemon and in the resolver routines and does not provide an API to this protocol.