Inter Stateful Path Computation Element communication procedures
draft-litkowski-pce-state-sync-01

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Last updated 2017-02-28
Replaces draft-dhody-pce-stateful-pce-lspdb-realtime-sync
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PCE Working Group                                           S. Litkowski
Internet-Draft                                                    Orange
Intended status: Standards Track                            S. Sivabalan
Expires: September 1, 2017                                         Cisco
                                                                D. Dhody
                                                                  Huawei
                                                       February 28, 2017

    Inter Stateful Path Computation Element communication procedures
                   draft-litkowski-pce-state-sync-01

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.
   The stateful PCE extensions allow stateful control of Multi-Protocol
   Label Switching (MPLS) Traffic Engineering Label Switched Paths (TE
   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 on a LSP to only a single PCE, and only one PCE
   is responsible for path computation for this delegated LSP.  The
   document does not state the procedures related to an inter-PCE
   stateful communication.

   There are some use cases, where an inter-PCE stateful communication
   can bring additional resiliency in the design for instance when some
   PCC-PCE sessions fails.  The inter-PCE stateful communication may
   also provide a faster update of the LSP states when 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 paths
   computation.

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

Litkowski, et al.       Expires September 1, 2017               [Page 1]
Internet-Draft                 state-sync                  February 2017

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on September 1, 2017.

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Table of Contents

   1.  Introduction and problem statement  . . . . . . . . . . . . .   3
     1.1.  Reporting LSP changes . . . . . . . . . . . . . . . . . .   3
     1.2.  Split-brain . . . . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Applicability to H-PCE  . . . . . . . . . . . . . . . . .  11
   2.  Proposed solution . . . . . . . . . . . . . . . . . . . . . .  11
     2.1.  State-sync session  . . . . . . . . . . . . . . . . . . .  11
     2.2.  Master/Slave relationship between PCE . . . . . . . . . .  13
   3.  Procedures and protocol extensions  . . . . . . . . . . . . .  13
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