Normative References in RFCs from Open Source
Jeff Tantsura, Joel Martin Halpern, Eliot Lear, Alia Atlas, Heather Flanagan · 2017
IETF procedures generally require that a standards track RFC may not have a normative reference to a non standards track specification except those from other standards bodies. This document creates an External Specification registry, similar to the DownRef registry that has been created based on [RFC3967] and permits normative references to community accepted external specifications.