Make-Before-Break MPLS-TE LSP restoration and reoptimization procedure using Stateful PCE

Stateful Path Computation Element (PCE) and its corresponding protocol extensions provide a mechanism that enables PCE to do stateful control of Multiprotocol Label Switching (MPLS) Traffic Engineering Label Switched Paths (TE LSP). Stateful PCE supports manipulating of the existing LSP's state and attributes (e.g., bandwidth and path) via delegation and also instantiation of new LSPs in the network via PCE Initiation procedures. In the current MPLS TE network using Resource ReSerVation Protocol (RSVP-TE), LSPs are often controlled by Make- before-break (M-B-B) signaling by the headend for the purpose of LSP restoration and reoptimization. In most cases, it is an essential operation to reroute LSP traffic without any data disruption. This document specifies the procedure of applying stateful PCE's control to make-before-break RSVP-TE signaling. In this document, two types of restoration/reoptimization procedures are defined, implicit mode and explicit mode. This document also specifies the usage and handling of stateful PCEP (PCE Communication Protocol) messages, expected behavior of PCC as RSVP-TE headend and necessary extensions of additional PCEP objects.