Applicability of a Stateful Path Computation Element (PCE)
RFC 8051

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Internet Engineering Task Force (IETF)                     X. Zhang, Ed.
Request for Comments: 8051                           Huawei Technologies
Category: Informational                                    I. Minei, Ed.
ISSN: 2070-1721                                             Google, Inc.
                                                            January 2017

       Applicability of a Stateful Path Computation Element (PCE)

Abstract

   A stateful Path Computation Element (PCE) maintains information about
   Label Switched Path (LSP) characteristics and resource usage within a
   network in order to provide traffic-engineering calculations for its
   associated Path Computation Clients (PCCs).  This document describes
   general considerations for a stateful PCE deployment and examines its
   applicability and benefits, as well as its challenges and
   limitations, through a number of use cases.  PCE Communication
   Protocol (PCEP) extensions required for stateful PCE usage are
   covered in separate documents.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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
   http://www.rfc-editor.org/info/rfc8051.

Zhang & Minei                 Informational                     [Page 1]
RFC 8051            Applicability for a Stateful PCE        January 2017

Copyright Notice

   Copyright (c) 2017 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Application Scenarios . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Optimization of LSP Placement . . . . . . . . . . . . . .   5
       3.1.1.  Throughput Maximization and Bin Packing . . . . . . .   6
       3.1.2.  Deadlock  . . . . . . . . . . . . . . . . . . . . . .   7
       3.1.3.  Minimum Perturbation  . . . . . . . . . . . . . . . .   9
       3.1.4.  Predictability  . . . . . . . . . . . . . . . . . . .  10
     3.2.  Auto-Bandwidth Adjustment . . . . . . . . . . . . . . . .  11
     3.3.  Bandwidth Scheduling  . . . . . . . . . . . . . . . . . .  12
     3.4.  Recovery  . . . . . . . . . . . . . . . . . . . . . . . .  12
       3.4.1.  Protection  . . . . . . . . . . . . . . . . . . . . .  13
       3.4.2.  Restoration . . . . . . . . . . . . . . . . . . . . .  14
       3.4.3.  SRLG Diversity  . . . . . . . . . . . . . . . . . . .  15
     3.5.  Maintenance of Virtual Network Topology (VNT) . . . . . .  15
     3.6.  LSP Reoptimization  . . . . . . . . . . . . . . . . . . .  16
     3.7.  Resource Defragmentation  . . . . . . . . . . . . . . . .  17
     3.8.  Point-to-Multipoint Applications  . . . . . . . . . . . .  17
     3.9.  Impairment-Aware Routing and Wavelength Assignment
           (IA-RWA)  . . . . . . . . . . . . . . . . . . . . . . . .  18
   4.  Deployment Considerations . . . . . . . . . . . . . . . . . .  19
     4.1.  Multi-PCE Deployments . . . . . . . . . . . . . . . . . .  19
     4.2.  LSP State Synchronization . . . . . . . . . . . . . . . .  19
     4.3.  PCE Survivability . . . . . . . . . . . . . . . . . . . .  19
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  20
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  21
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  22
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

Zhang & Minei                 Informational                     [Page 2]
RFC 8051            Applicability for a Stateful PCE        January 2017