http://www.rfc-editor.org/rfc/rfc5991.txt
RFC 5991: Teredo Security Updates, D. Thaler, S. Krishnan, J. Hoagland2010-09-01T23:00:00-00:00The Teredo protocol defines a set of flags that are embedded in every Teredo IPv6 address. This document specifies a set of security updates that modify the use of this flags field, but are backward compatible. [STANDARDS-TRACK]