An engineer needs to improve MPLS network management by implementing a set of tools to support the NOC engineers in troubleshooting network failures. Which feature should the engineer implement to check the connectivity of the MPLS LSP between the ingress and egress PE routers?

MPLS Operations, Administration, and Maintenance (OAM) is a suite of protocols and tools designed specifically for fault detection and diagnostics in an MPLS network. The primary tool within MPLS OAM for this purpose is LSP Ping (and LSP Traceroute), defined in RFC 8029. LSP Ping sends an "MPLS echo request" packet that traverses the exact same Label Switched Path (LSP) as data traffic from the ingress to the egress PE. The egress PE then sends an "MPLS echo reply" back, confirming data plane connectivity and integrity of the LSP. This directly fulfills the engineer's requirement to provide a tool for troubleshooting LSP failures.

B. MPLS-TP: This is a specific profile of MPLS designed for transport networks. While it includes enhanced OAM, it is an entire architecture, not the specific feature for checking LSP connectivity.
C. LDP autodiscovery: This is a control plane mechanism used by the Label Distribution Protocol (LDP) to find potential neighbors, not a tool for verifying an established data plane path.
D. extended ping: This is a standard IP-level ICMP tool. It tests IP reachability but is unaware of the underlying MPLS labels and cannot verify the integrity of the specific LSP data plane path.

1. Cisco Systems, Inc. (2023). MPLS Basic Configuration Guide, Cisco IOS XE Amsterdam 17.3.x - MPLS Operations, Administration, and Maintenance (OAM). "MPLS OAM provides tools to manage and administer an MPLS network. It is used to detect, isolate, and diagnose failures in the MPLS network. The main features of MPLS OAM are LSP ping and LSP traceroute." (Section: MPLS Operations, Administration, and Maintenance (OAM)).

2. Aggarwal, R., Kompella, K., & Nadeau, T. (2017). RFC 8029: Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures. Internet Engineering Task Force (IETF). "This document describes a simple and efficient mechanism that can be used to detect data-plane failures in Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs). This mechanism is referred to as 'LSP Ping'." (Abstract, Section 1).

3. Cisco Systems, Inc. (2021). MPLS Command Reference, Cisco IOS XE Gibraltar 16.12.x - ping mpls. "To check the connectivity of a specified Multiprotocol Label Switching (MPLS) label switched path (LSP), use the ping mpls command in privileged EXEC mode. [...] This command invokes the MPLS LSP ping feature, which is part of MPLS OAM." (Command Description section).