http://www.rfc-editor.org/rfc/rfc5304.txt
RFC 5304: IS-IS Cryptographic Authentication, T. Li, R. Atkinson2008-10-01T23:00:00-00:00This document proposes an extension to that specification that allows the use of the HMAC-MD5 authentication algorithm to be used in conjunction with the existing authentication mechanisms. [STANDARDS-TRACK]