http://www.rfc-editor.org/rfc/rfc6213.txt
RFC 6213: IS-IS BFD-Enabled TLV, C. Hopps, L. Ginsberg2011-04-01T23:00:00-00:00This document describes a type-length-value (TLV) for use in the IS-IS routing protocol that allows for the proper use of the Bidirectional Forwarding Detection (BFD) protocol. There exist certain scenarios in which IS-IS will not react appropriately to a BFD-detected forwarding plane failure without use of either this TLV or some other method. [STANDARDS-TRACK]