[Pce] I-D Action: draft-ietf-pce-state-sync-00.txt

internet-drafts@ietf.org Tue, 29 June 2021 02:56 UTC

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Subject: [Pce] I-D Action: draft-ietf-pce-state-sync-00.txt
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A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Path Computation Element WG of the IETF.

        Title           : Inter Stateful Path Computation Element (PCE) Communication Procedures.
        Authors         : Stephane Litkowski
                          Siva Sivabalan
                          Cheng Li
                          Haomian Zheng
	Filename        : draft-ietf-pce-state-sync-00.txt
	Pages           : 32
	Date            : 2021-06-28

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computation in response to a Path Computation Client (PCC) request.
   The Stateful PCE extensions allow stateful control of Multi-Protocol
   Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths
   (LSPs) using PCEP.

   A Path Computation Client (PCC) can synchronize an LSP state
   information to a Stateful Path Computation Element (PCE).  The
   stateful PCE extension allows a redundancy scenario where a PCC can
   have redundant PCEP sessions towards multiple PCEs.  In such a case,
   a PCC gives control of a LSP to only a single PCE, and only one PCE
   is responsible for path computation for this delegated LSP.

   There are some use cases, where an inter-PCE stateful communication
   can bring additional resiliency in the design, for instance when some
   PCC-PCE session fails.  The inter-PCE stateful communication may also
   provide a faster update of the LSP states when such an event occurs.
   Finally, when, in a redundant PCE scenario, there is a need to
   compute a set of paths that are part of a group (so there is a
   dependency between the paths), there may be some cases where the
   computation of all paths in the group is not handled by the same PCE:
   this situation is called a split-brain.  This split-brain scenario
   may lead to computation loops between PCEs or suboptimal path

   This document describes the procedures to allow a stateful
   communication between PCEs for various use-cases and also the
   procedures to prevent computations loops.

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