Juniper Networks Juniper Networks Ericsson The MPLS echo request and MPLS echo response messages, defined in RFC 8029 "Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures" (usually referred to as LSP ping messages), are encapsulated in IP headers that include a Router Alert Option (RAO). The rationale for using an RAO as the exception mechanism is questionable. Furthermore, RFC 6398 identifies security vulnerabilities associated with the RAO in non-controlled environments, e.g., the case of using the MPLS echo request/reply as inter-area OAM, and recommends against its use outside of controlled environments. Therefore, this document removes the RAO from LSP ping message encapsulations. It updates RFCs 7506 and 8029. This document also recommends the use of an IPv6 loopback address (::1/128) and discourages the use of an IPv4 loopback address mapped to IPv6.