IPv6 Mapping Prefix PDU for the RPKI-Router Protocol

This document defines a new Protocol Data Unit (PDU) type for the RPKI to Router Protocol to convey Mapping Origin Authorization (MOA) information from RPKI caches to routers. The new PDU, named the "IPv6 Mapping Prefix" PDU, carries the authorization mapping between one or more IPv4 prefixes and their corresponding authorized IPv6 mapping prefix. This extension enables routers to perform Mapping Origin Validation (MOV) for IPv4-to-IPv6 address mapping announcements in IPv6-only underlay networks.