Path MTU (PMTU) for Segment Routing (SR) Policy

This document defines the Path MTU (PMTU) for Segment Routing (SR) Policy (called SR-PMTU). It applies to both Segment Routing over IPv6 (SRv6) and SR-MPLS. This document specifies the framework of SR-PMTU for SR Policy including the link MTU collection, the SR-PMTU computation, the SR-PMTU enforcement, and the handling behaviours on the headend.