http://www.rfc-editor.org/rfc/rfc7585.txt
RFC 7585: Dynamic Peer Discovery for RADIUS/TLS and RADIUS/DTLS Based on the Network Access Identifier (NAI), S. Winter, M. McCauley2015-10-01T23:00:00-00:00This document specifies a means to find authoritative RADIUS servers for a given realm. It is used in conjunction with either RADIUS over Transport Layer Security (RADIUS/TLS) or RADIUS over Datagram Transport Layer Security (RADIUS/DTLS).