The Generalized TTL Security Mechanism (GTSM)

UDP Usage Guidelines

“…The Generalized TTL Security Mechanism (GTSM) [RFC5082] may be used with UDP applications when the intended endpoint is on the same link as the sender. This lightweight mechanism allows a receiver to filter unwanted packets.…”

The Generalized TTL Security Mechanism (GTSM) for the Label Distribution Protocol (LDP)

“…Additionally, the GTSM for LDP specified in this document applies only to single-hop LDP peering sessions and not to multi-hop LDP peering sessions, in line with Section 5.5 of [RFC5082]. Consequently, any LDP method or feature (such as LDP IGP Synchronization [RFC5443] or LDP Session Protection [LDP-SPROT]) that relies on multi-hop LDP peering sessions would not work with GTSM and will require (statically or dynamically) disabling the GTSM capability.…”

“…The Generalized TTL Security Mechanism (GTSM) [RFC5082] is a mechanism based on IPv4 Time To Live (TTL) or IPv6 Hop Limit value verification so as to provide a simple and reasonably robust defense from infrastructure attacks using forged protocol packets from outside the network. GTSM can be applied to any protocol peering session that is established between routers that are adjacent.…”

“…Sending and Receiving procedures for LDP Link Hello message 3. Sending and Receiving procedures for LDP Initialization message GTSM specifies that "it SHOULD NOT be enabled by default in order to remain backward compatible with the unmodified protocol" (see Section 3 of [RFC5082]). This document specifies a "built-in dynamic GTSM capability negotiation" for LDP to suggest the use of GTSM.…”

Transparent Interconnection of Lots of Links (TRILL): Bidirectional Forwarding Detection (BFD) Support

“…To prevent spoofing attacks, the TRILL hop count of a received session is checked [RFC5082]. For a single-hop session, if the hop count is less than 0x3F and the RBridge Channel Header MH flag is zero, the packet is discarded.…”