In general, a zone is an area of administration. The meaning is similar to that of domain. Specific networking environments use the term to mean somewhat different things:
1) In the domain name system (DNS) environment, a zone is the name space allocated for a particular server. A zone file maintains instructions for resolving specified Internet domain names to the appropriate number form of an Internet Protocol address (an IP address).
2) In an H.323 multimedia network, a zone is a group of terminals, multipoint control units (MCUs), and gateways within a particular domain. A zone may be a relatively permanent configuration of devices, or just a runtime entity established for a particular event. An administrative tool called a gatekeeper controls interactions for each zone.