Ability for a Stateful Path Computation Element (PCE) to Request and Obtain Control of a Label Switched Path (LSP)
RFC 8741

Document Type RFC - Proposed Standard (March 2020; No errata)
Last updated 2020-03-09
Replaces draft-raghu-pce-lsp-control-request
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Internet Engineering Task Force (IETF)                       A. Raghuram
Request for Comments: 8741                                    A. Goddard
Category: Standards Track                                           AT&T
ISSN: 2070-1721                                               J. Karthik
                                                            S. Sivabalan
                                                     Cisco Systems, Inc.
                                                                 M. Negi
                                                     Huawei Technologies
                                                              March 2020

  Ability for a Stateful Path Computation Element (PCE) to Request and
             Obtain Control of a Label Switched Path (LSP)

Abstract

   A stateful Path Computation Element (PCE) retains information about
   the placement of Multiprotocol Label Switching (MPLS) Traffic
   Engineering Label Switched Paths (TE LSPs).  When a PCE has stateful
   control over LSPs, it may send indications to LSP head-ends to modify
   the attributes (especially the paths) of the LSPs.  A Path
   Computation Client (PCC) that has set up LSPs under local
   configuration may delegate control of those LSPs to a stateful PCE.

   There are use cases in which a stateful PCE may wish to obtain
   control of locally configured LSPs that it is aware of but have not
   been delegated to the PCE.

   This document describes an extension to the Path Computation Element
   Communication Protocol (PCEP) to enable a PCE to make requests for
   such control.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8741.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document.  Please review these documents
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   to this document.  Code Components extracted from this document must
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Terminology
     2.1.  Requirements Language
   3.  LSP Control Request Flag
   4.  Operation
   5.  Security Considerations
   6.  IANA Considerations
   7.  Manageability Considerations
     7.1.  Control of Function and Policy
     7.2.  Information and Data Models
     7.3.  Liveness Detection and Monitoring
     7.4.  Verify Correct Operations
     7.5.  Requirements on Other Protocols
     7.6.  Impact on Network Operations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   "Path Computation Element Communication Protocol (PCEP) Extensions
   for Stateful PCE" [RFC8231] specifies a set of extensions to PCEP
   [RFC5440] to enable stateful control of Traffic Engineering Label
   Switched Paths (TE LSPs) between and across PCEP sessions in
   compliance with [RFC4657].  It includes mechanisms to synchronize LSP
   state between Path Computation Clients (PCCs) and PCEs, delegate
   control of LSPs to PCEs, and allow PCEs to control the timing and
   sequence of path computations within and across PCEP sessions.  The
   stateful PCEP defines the following two useful network operations:

   Delegation:  As per [RFC8051], an operation to grant a PCE temporary
                rights to modify a subset of LSP parameters on one or
                more LSPs of a PCC.  LSPs are delegated from a PCC to a
                PCE and are referred to as "delegated" LSPs.

   Revocation:  As per [RFC8231], an operation performed by a PCC on a
                previously delegated LSP.  Revocation revokes the rights
                granted to the PCE in the delegation operation.

   For redundant stateful PCEs (Section 5.7.4 of [RFC8231]), during a
   PCE failure, one of the redundant PCEs might want to request to take
   control over an LSP.  The redundant PCEs may use a local policy or a
   proprietary election mechanism to decide which PCE would take
   control.  In this case, a mechanism is needed for a stateful PCE to
   request control of one or more LSPs from a PCC so that a newly
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