https://datatracker.ietf.org/doc/draft-ietf-rtgwg-rfc3682bis/10/
draft-ietf-rtgwg-rfc3682bis-10 - The Generalized TTL Security Mechanism (GTSM)
The use of a packet's Time to Live (TTL) (IPv4) or Hop Limit (IPv6) to verify whether the packet was originated by an adjacent node on a connected link has...
draftietfrtgwg