https://datatracker.ietf.org/doc/rfc3845/
RFC 3845 - DNS Security (DNSSEC) NextSECure (NSEC) RDATA Format
This document redefines the wire format of the "Type Bit Map" field in the DNS NextSECure (NSEC) resource record RDATA format to cover the full resource record...
dns securityrfcdnssecnsecformat