Requirements for Hitless MPLS Path Segment Monitoring

One of the most important Operations, Administration, and Maintenance (OAM) capabilities for transport-network operation is fault localization. An in-service, on-demand path segment monitoring function of a transport path is indispensable, particularly when the service monitoring function is activated only between endpoints. However, the current segment monitoring approach defined for MPLS (including the MPLS Transport Profile (MPLS-TP)) in RFC 6371 "Operations, Administration, and Maintenance Framework for MPLS-Based Transport Networks" has drawbacks. This document provides an analysis of the existing MPLS-TP OAM mechanisms for the path segment monitoring and provides requirements to guide the development of new OAM tools to support Hitless Path Segment Monitoring (HPSM).