Cisco Systems Cisco Systems Cisco Systems Huawei Huawei The Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Ping and Traceroute use the Reply Mode field to signal the method to be used in the MPLS echo reply. This document adds one value to the Reply Mode field to indicate reverse LSP. This document also adds an optional TLV which can carry ordered list of Reply Mode values. This document updates RFC4379.