http://www.rfc-editor.org/rfc/rfc5478.txt
RFC 5478: IANA Registration of New Session Initiation Protocol (SIP) Resource-Priority Namespaces, J. Polk2009-03-01T23:00:00-00:00This document creates additional Session Initiation Protocol (SIP) Resource-Priority namespaces to meet the requirements of the US Defense Information Systems Agency, and places these namespaces in the IANA registry. [STANDARDS-TRACK]