LSP Ping/Traceroute for Prefix SID in Multi-Algorithm/Multi-Topology Networks

[RFC8287] defines the extensions to MPLS LSP Ping and Traceroute for Segment Routing IGP-Prefix and IGP-Adjacency Segment Identifier (SIDs) with an MPLS data plane. The machinery defined in [RFC8287] works well in single topology, single algorithm deployments where each Prefix SID is only associated with a single IP prefix. In multi-topology networks, or networks deploying multiple algorithms for the same IP Prefix, MPLS echo request needs to carry additional information in the Target FEC Stack sub-TLVs to properly validate IGP Prefix SID. This document updates [RFC8287] by modifying IPv4 and IPv6 IGP-Prefix Segment ID FEC sub-TLVs to also include algorithm identification while maintaining backwards compatibility. This document also introduces new Target FEC Stack sub-TLVs for Prefix SID validation in multi-topology networks.