http://www.rfc-editor.org/rfc/rfc7886.txt
RFC 7886: Advertising Seamless Bidirectional Forwarding Detection (S-BFD) Discriminators in the Layer Two Tunneling Protocol Version 3 (L2TPv3), V. Govindan, C. Pignataro2016-07-01T23:00:00-00:00This document defines a new Attribute-Value Pair (AVP) that allows L2TP Control Connection Endpoints (LCCEs) to advertise one or more Seamless Bidirectional Forwarding Detection (S-BFD) Discriminator values using the Layer Two Tunneling Protocol version 3 (L2TPv3).