Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing
RFC 8664

Document Type RFC - Proposed Standard (December 2019; No errata)
Updates RFC 8408
Authors Siva Sivabalan  , Clarence Filsfils  , Jeff Tantsura  , Wim Henderickx  , Jonathan Hardwick 
Last updated 2019-12-06
Replaces draft-sivabalan-pce-segment-routing
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Internet Engineering Task Force (IETF)                      S. Sivabalan
Request for Comments: 8664                                   C. Filsfils
Updates: 8408                                        Cisco Systems, Inc.
Category: Standards Track                                    J. Tantsura
ISSN: 2070-1721                                             Apstra, Inc.
                                                           W. Henderickx
                                                             J. Hardwick
                                                     Metaswitch Networks
                                                           December 2019

 Path Computation Element Communication Protocol (PCEP) Extensions for
                            Segment Routing


   Segment Routing (SR) enables any head-end node to select any path
   without relying on a hop-by-hop signaling technique (e.g., LDP or
   RSVP-TE).  It depends only on "segments" that are advertised by link-
   state Interior Gateway Protocols (IGPs).  An SR path can be derived
   from a variety of mechanisms, including an IGP Shortest Path Tree
   (SPT), an explicit configuration, or a Path Computation Element
   (PCE).  This document specifies extensions to the Path Computation
   Element Communication Protocol (PCEP) that allow a stateful PCE to
   compute and initiate Traffic-Engineering (TE) paths, as well as a
   Path Computation Client (PCC) to request a path subject to certain
   constraints and optimization criteria in SR networks.

   This document updates RFC 8408.

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

Copyright Notice

   Copyright (c) 2019 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
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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
   2.  Terminology
     2.1.  Requirements Language
   3.  Overview of PCEP Operation in SR Networks
   4.  Object Formats
     4.1.  The OPEN Object
       4.1.1.  The Path Setup Type Capability TLV
       4.1.2.  The SR PCE Capability Sub-TLV
     4.2.  The RP/SRP Object
     4.3.  ERO
       4.3.1.  SR-ERO Subobject
       4.3.2.  NAI Associated with SID
     4.4.  RRO
     4.5.  METRIC Object
   5.  Procedures
     5.1.  Exchanging the SR PCE Capability
     5.2.  ERO Processing
       5.2.1.  SR-ERO Validation
       5.2.2.  Interpreting the SR-ERO
     5.3.  RRO Processing
   6.  Management Considerations
     6.1.  Controlling the Path Setup Type
     6.2.  Migrating a Network to Use PCEP Segment-Routed Paths
     6.3.  Verification of Network Operation
     6.4.  Relationship to Existing Management Models
   7.  Security Considerations
   8.  IANA Considerations
     8.1.  PCEP ERO and RRO Subobjects
     8.2.  New NAI Type Registry
     8.3.  New SR-ERO Flag Registry
     8.4.  PCEP-Error Object
     8.5.  PCEP TLV Type Indicators
     8.6.  PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators
     8.7.  New Path Setup Type
     8.8.  New Metric Type
     8.9.  SR PCE Capability Flags
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Appendix A.  Compatibility with Early Implementations
   Authors' Addresses

1.  Introduction

   Segment Routing (SR) leverages the source-routing paradigm.  Using
   SR, a source node steers a packet through a path without relying on
   hop-by-hop signaling protocols such as LDP or RSVP-TE.  Each path is
   specified as an ordered list of instructions called "segments".  Each
   segment is an instruction to route the packet to a specific place in
   the network or to perform a function on the packet.  A database of
   segments can be distributed through the network using a routing
   protocol (such as IS-IS or OSPF) or by any other means.  Several
   types of segments are defined.  A node segment uniquely identifies a
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