http://www.rfc-editor.org/rfc/rfc6393.txt
RFC 6393: Moving RFC 4693 to Historic, M. Yevstifeyev2011-09-01T23:00:00-00:00This document moves RFC 4693 to Historic status. It also obsoletes RFC 4693. This document is not an Internet Standards Track specification; it is published for informational purposes.