Path Protection Enforcement in PCEP
draft-stone-pce-path-protection-enforcement-00

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Network Working Group                                           A. Stone
Internet-Draft                                               M. Aissaoui
Intended status: Standards Track                                   Nokia
Expires: April 27, 2020                                 October 25, 2019

                  Path Protection Enforcement in PCEP
             draft-stone-pce-path-protection-enforcement-00

Abstract

   This document aims to clarify existing usage of the local protection
   desired bit signalled in Path Computation Element Protocol (PCEP).
   This document also introduces a new flag for signalling protection
   strictness in PCEP.

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 April 27, 2020.

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Stone & Aissaoui         Expires April 27, 2020                 [Page 1]
Internet-Draft                     I-D                      October 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Protection Enforcement Flag (E-Flag)  . . . . . . . . . . . .   4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  LSP Attributes Protection Enforcement Flag  . . . . . . .   6
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Path Computation Element (PCE) Communication Protocol (PCEP)
   [RFC5440] enables the communication between a Path Computation Client
   (PCC) and a Path Control Element (PCE), or between two PCEs based on
   the PCE architecture [RFC4655] .

   PCEP [RFC5440] utilizes flags, values and concepts previously defined
   in RSVP-TE Extensions [RFC3209] and Fast Reroute Extensions to RSVP-
   TE [RFC4090] . One such concept in PCEP is the "Local Protection
   Desired" (L-flag in the LSPA Object in RFC5440), which was originally
   defined in the SESSION-ATTRIBUTE Object in RFC3209.  In RSVP, this
   flag signals to downstream routers that local protection is desired,
   which indicates to transit routers that they may use a local repair
   mechanism.  The headend router calculating the path does not know
   whether a downstream router will or will not protect a hop during
   it's calculation.  Therefore, a local protection desired does not
   require the transit router to satisfy protection in order to
   establish the RSVP signalled path.  This flag is signalled in PCEP as
   an attribute of the LSP via the LSP Attributes object.

   PCEP Extensions for Segment Routing (draft-ietf-pce-segment-routing)
   extends support in PCEP for Segment Routed LSPs (SR-LSPs) as defined
   in the Segment Routing Architecture [RFC8402] . As per the Segment
   Routing Architecture, Adjacency Segment Identifiers(Adj-SID) may be
   eligible for protection (using IPFRR or MPLS-FRR).  The protection
   eligibility is advertised into IGP (draft-ietf-ospf-segment-routing-
   extensions and draft-ietf-isis-segment-routing-extensions) as the
   B-Flag part of the Adjacency SID sub-tlv and can be discovered by a
   PCE via BGP-LS [RFC7752] using the BGP-LS Segment Routing Extensions
   (draft-ietf-idr-bgp-ls-segment-routing-ext).  An Adjacency SID may or
   may not have protection eligibility and for a given adjacency between
   two routers there may be multiple Adjacency SIDs, some of which are
   protected and some which are not.

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