Carrying SID Algorithm information in PCE-based Networks.
draft-tokar-pce-sid-algo-00

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Last updated 2019-07-03
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PCE Working Group                                               A. Tokar
Internet-Draft                                              S. Sivabalan
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: January 1, 2020                                         M. Negi
                                                     Huawei Technologies
                                                           June 30, 2019

       Carrying SID Algorithm information in PCE-based Networks.
                      draft-tokar-pce-sid-algo-00

Abstract

   The Algorithm associated with a prefix Segment-ID (SID) defines the
   path computation Algorithm used by Interior Gateway Protocols (IGPs).
   This information is available to controllers such as the Path
   Computation Element (PCE) via topology learning.  This document
   proposes an approach for informing headend routers regarding the
   Algorithm associated with each prefix SID used in PCE-computed paths.

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].

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Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Internet-Draft            SID Algorithm in PCEP                June 2019

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SR ERO NAI Extensions . . . . . . . . . . . . . . . . . . . .   3
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  PCEP SR-ERO NAI Types . . . . . . . . . . . . . . . . . .   4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   A PCE can compute SR-TE paths using prefix SIDs with different
   Algorithms depending on the use-case, constraints, etc.  While this
   information is available on the PCE, there is no method of conveying
   this information to the headend router.

   Similarly, the headend can also compute SR-TE paths using different
   Algorithms, and this information also needs to be conveyed to the PCE
   for collection or troubleshooting purposes.  In addition, in the case
   of multiple (redundant) PCEs, when the headend receives a path from
   the primary PCE, it needs to be able to report the complete path
   information - including the Algorithm - to the backup PCE so that in
   HA scenarios, the backup PCE can verify the prefix SIDs
   appropriately.

   Refer to [I-D.ietf-ospf-segment-routing-extensions] and
   [I-D.ietf-isis-segment-routing-extensions] for details about the
   prefix SID Algorithm.

   This document introduces two new NAI types for the SR-ERO subobject,
   which is defined in [I-D.ietf-pce-segment-routing].

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2.  Terminology

   The following terminologies are used in this document:

   ERO:  Explicit Route Object

   IGP:  Interior Gateway Protocol

   NAI:  Node or Adjacency Identifier.

   PCE:  Path Computation Element

   PCEP:  Path Computation Element Protocol.

   SID:  Segment Identifier.

   SR:  Segment Routing.

   SR-TE:  Segment Routing Traffic Engineering.
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