http://www.rfc-editor.org/rfc/rfc6218.txt
RFC 6218: Cisco Vendor-Specific RADIUS Attributes for the Delivery of Keying Material, G. Zorn, T. Zhang, J. Walker, J. Salowey2011-04-01T23:00:00-00:00This document defines a set of vendor-specific RADIUS Attributes designed to allow both the secure transmission of cryptographic keying material and strong authentication of any RADIUS message. These attributes have been allocated from the Cisco vendor-specific space and have been implemented by multiple vendors. This document is not an Internet Standards Track specification; it is published for informational purposes.