Netopia Router PN Series - Manual (Page 289)

GL-19
zone: An arbitrary subset of nodes within an AppleTalk internet.
Creating multiple zones makes it easier for users to locate network
services. The network administrator defines zones when he or she
configures routers. Isolated networks have no zones. LocalTalk and
EtherTalk Phase I networks may have no more than one zone each.
EtherTalk Phase II and TokenTalk networks may have more than one
zone each. Several networks of any AppleTalk type may share a zone
name.