The IN-ADDR.ARPA zone is a critical service for Internet operations as it provides a guaranteed method to perform host address to host name mapping. The delegations which exist in this zone represent the ‘/8’ IPv4 delegations to the registrants of the corresponding IANA function allocations to legacy registrants and Regional Internet Registries. Since 1997 ARIN has performed technical management function of zone editor and zone generator as inherited from InterNIC.
The IN-ADDR.ARPA zone is a sub domain of the ARPA top-level domain. ARPA sub domain management principles, management guidelines and operational requirements are described in RFC 3172.