http://www.rfc-editor.org/rfc/rfc3553.txt
RFC 3553: An IETF URN Sub-namespace for Registered Protocol Parameters, M. Mealling, L. Masinter, T. Hardie, G. Klyne2003-06-01T23:00:00-00:00This document describes a new sub-delegation for the 'ietf' URN namespace for registered protocol items. The 'ietf' URN namespace is defined in RFC 2648 as a root for persistent URIs that refer to IETF- defined resources. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.