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PCE Working Group                                                  C. Li
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                D. Dhody
Expires: March 16, 2019                              Huawei Technologies
                                                                W. Cheng
                                                            China Mobile
                                                                 J. Dong
                                                                   Z. Li
                                                     Huawei Technologies
                                                               R. Gandhi
                                                     Cisco Systems, Inc.
                                                      September 12, 2018


  Path Computation Element Communication Protocol (PCEP) Extension for
              Path Identification in Segment Routing (SR)
                    draft-li-pce-sr-path-segment-02

Abstract

   The Path Computation Element (PCE) provides path computation
   functions in support of traffic engineering in Multiprotocol Label
   Switching (MPLS) and Generalized MPLS (GMPLS) networks.

   The Source Packet Routing in Networking (SPRING) architecture
   describes how Segment Routing (SR) can be used to steer packets
   through an IPv6 or MPLS network using the source routing paradigm.  A
   Segment Routed Path can be derived from a variety of mechanisms,
   including an IGP Shortest Path Tree (SPT), explicit configuration, or
   a Path Computation Element (PCE).

   Path identification is needed for several use cases such as
   performance measurement in Segment Routing (SR) network.  This
   document specifies extensions to the Path Computation Element
   Protocol (PCEP) to support requesting, replying, reporting and
   updating the path identifier between PCEP speakers.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.







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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 16, 2019.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview of Path ID Extensions in PCEP  . . . . . . . . . . .   4
   4.  Objects and TLVs  . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  The OPEN Object . . . . . . . . . . . . . . . . . . . . .   5
       4.1.1.  The SR PCE Capability sub-TLV . . . . . . . . . . . .   5
       4.1.2.  The SRv6 PCE Capability sub-TLV . . . . . . . . . . .   6
       4.1.3.  PCECC-CAPABILITY sub-TLV  . . . . . . . . . . . . . .   6
     4.2.  LSP Object  . . . . . . . . . . . . . . . . . . . . . . .   7
       4.2.1.  Path ID TLV . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  FEC Object  . . . . . . . . . . . . . . . . . . . . . . .   9
     4.4.  CCI Object  . . . . . . . . . . . . . . . . . . . . . . .  10
   5.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.1.  PCC Allocated Path ID . . . . . . . . . . . . . . . . . .  11



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       5.1.1.  Egress PCC Allocated Path ID  . . . . . . . . . . . .  12
       5.1.2.  Ingress PCC Allocated Path ID . . . . . . . . . . . .  16
     5.2.  PCE Allocated Path ID . . . . . . . . . . . . . . . . . .  17
       5.2.1.  PCE Controlled ID Spaces Advertisement  . . . . . . .  17
       5.2.2.  Ingress PCC request Path ID to PCE  . . . . . . . . .  17
       5.2.3.  PCE allocated Path ID on its own  . . . . . . . . . .  18
     5.3.  Two Label Solution  . . . . . . . . . . . . . . . . . . .  19
   6.  Dataplane Considerations  . . . . . . . . . . . . . . . . . .  19
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  SR PCE Capability Flags . . . . . . . . . . . . . . . . .  20
     7.2.  SRv6 PCE Capability Flags . . . . . . . . . . . . . . . .  20
     7.3.  New LSP Flag Registry . . . . . . . . . . . . . . . . . .  20
     7.4.  New PCEP TLV  . . . . . . . . . . . . . . . . . . . . . .  21
       7.4.1.  Path ID TLV . . . . . . . . . . . . . . . . . . . . .  21
     7.5.  New CCI Flag Registry . . . . . . . . . . . . . . . . . .  21
     7.6.  New FEC Type Registry . . . . . . . . . . . . . . . . . .  22
     7.7.  PCEP Error Type and Value . . . . . . . . . . . . . . . .  22
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  22
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  22
     10.2.  Informative References . . . . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

   [RFC5440] describes the Path Computation Element (PCE) Communication
   Protocol (PCEP).  PCEP enables the communication between a Path
   Computation Client (PCC) and a PCE, or between PCE and PCE, for the
   purpose of computation of Multiprotocol Label Switching (MPLS) as
   well as Generalzied MPLS (GMPLS) Traffic Engineering Label Switched
   Path (TE LSP) characteristics.

   [RFC8231] specifies a set of extensions to PCEP to enable stateful
   control of TE LSPs within and across PCEP sessions in compliance with
   [RFC4657].  It includes mechanisms to effect LSP State
   Synchronization between PCCs and PCEs, delegation of control over
   LSPs to PCEs, and PCE control of timing and sequence of path
   computations within and across PCEP sessions.  The model of operation
   where LSPs are initiated from the PCE is described in [RFC8281].

   [I-D.zhao-pce-pcep-extension-for-pce-controller] specify the
   procedures and PCEP protocol extensions for using the PCE as the
   central controller for static LSPs, where LSPs can be provisioned as
   explicit label instructions at each hop on the end-to-end path.






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   Segment routing (SR) [RFC8402] leverages the source routing and
   tunneling paradigms and supports steering packets into an explicit
   forwarding path at the ingress node.

   An SR path needs to be identified in some use cases such as
   performance measurement.  For identifying an SR path,
   [I-D.cheng-spring-mpls-path-segment] introduces a new segment that is
   referred to as Path Segment.

   [I-D.ietf-pce-segment-routing] specifies extensions to the Path
   Computation Element Protocol (PCEP) [RFC5440] for SR networks, that
   allow a stateful PCE to compute and initiate SR-TE paths, as well as
   a PCC to request, report or delegate SR paths.
   [I-D.negi-pce-segment-routing-ipv6] extend PCEP to support SR for
   IPv6 data plane.

   [I-D.zhao-pce-pcep-extension-pce-controller-sr] specifies the
   procedures and PCEP protocol extensions when a PCE-based controller
   is also responsible for configuring the forwarding actions on the
   routers (SR SID distribution in this case), in addition to computing
   the paths for packet flows in a segment routing network and telling
   the edge routers what instructions to attach to packets as they enter
   the network.

   This document specifies a mechanism to carry the SR path
   identification information in PCEP messages [RFC5440] [RFC8231]
   [RFC8281].  The path ID can be a path segment in SR-MPLS
   [I-D.cheng-spring-mpls-path-segment], or a path ID in SRv6
   [I-D.li-spring-passive-pm-for-srv6-np], or other IDs that can
   identify the SR path.  This document also extends the PCECC-SR
   mechanism to inform the path ID to the egress PCC.

2.  Terminology

   This memo makes use of the terms defined in [RFC4655],
   [I-D.ietf-pce-segment-routing], and [RFC8402].

3.  Overview of Path ID Extensions in PCEP

   This document specifies a mechanism of encoding (and allocating) path
   ID (path segment in case of MPLS, path ID in case of IPv6, etc) in
   PCEP extensions.  For supporting path ID in PCEP, several TLVs and
   flags are defined.  The formats of the objects and TLVs are described
   in Section 4.  The procedures of path ID allocation are described in
   Section 5.

   There are various modes of operations, such as -




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   o  The path ID can be allocated by Egress PCC.  The PCE should
      request the Path ID from Egress PCC.

   o  The path ID can be allocated by Ingress PCC itself and informed to
      the PCE.  The PCE can then inform the egress PCC.

   o  Ingress PCC can also request PCE to allocate the path ID, in this
      case, the PCE would allocate and inform the assigned path ID to
      the ingress/egress PCC using PCEP messages.

   o  The PCE can allocate a path ID on its own accord and inform the
      ingress/egress PCC , useful for PCE-initiated LSPs.

   The path information to the ingress PCC and PCE is exchanged via an
   extension to [I-D.ietf-pce-segment-routing] and
   [I-D.negi-pce-segment-routing-ipv6].  The path ID information to the
   egress PCC is informed via an extension to the PCECC-SR procedures
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].

   For the PCE to allocate a path ID, the PCE SHOULD be aware of the
   path ID space from the PCCs.  This is done via mechanism as described
   in [I-D.li-pce-controlled-id-space].  Otherwise, the PCE should
   request the egress PCC of Path IDs.

4.  Objects and TLVs

4.1.  The OPEN Object

4.1.1.  The SR PCE Capability sub-TLV

   [I-D.ietf-pce-segment-routing] defined a new Path Setup Type (PST)
   and SR-PCE-CAPABILITY sub-TLV for SR.  PCEP speakers use this sub-TLV
   to exchange information about their SR capability.  The TLV includes
   a Flags field and one bit (L-flag) was allocated in
   [I-D.ietf-pce-segment-routing].

   This document adds an additional flag for path ID allocation, as
   follows -

      P (Path Identification bit): A PCEP speaker sets this flag to 1 to
      indicate that it has the capability to encode SR path
      identification (path segment, as per
      [I-D.cheng-spring-mpls-path-segment]).








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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type=26            |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |   Flags |P|N|L|      MSD      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 1: P-flag in SR-PCE-CAPABILITY TLV

   The figure is included for the ease of the reader and can be removed
   at the time of publication.

4.1.2.  The SRv6 PCE Capability sub-TLV

   [I-D.negi-pce-segment-routing-ipv6] defined a new Path Setup Type
   (PST) and SRv6-PCE-CAPABILITY sub-TLV for SRv6.  PCEP speakers use
   this sub-TLV to exchange information about their SRv6 capability.
   The TLV includes a Flags field and one bit (L-flag) was allocated in
   [I-D.negi-pce-segment-routing-ipv6].

   This document adds an additional flag for path ID allocation, as
   follows -

      P (Path Identification bit): A PCEP speaker sets this flag to 1 to
      indicate that it has the capability to encode SRv6 path
      identification.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type=TBD1          |            Length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      max-SL   |  Reserved     |             Flags         |P|L|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 2: P-flag in SRv6-PCE-CAPABILITY TLV

   The figure is included for the ease of the reader and can be removed
   at the time of publication.

4.1.3.  PCECC-CAPABILITY sub-TLV

   Along with the SR sub-TLVs, the PCECC Capability as per
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] should be advertised
   if the PCE allocates the path identifier and acts as a Central
   Controller that manages the Label (Path ID) space.




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   The PCECC Capability should also be advertised on the egress PCEP
   session, along with the SR sub-TLVs.  This is needed to ensure that
   the PCE can use the PCECC objects/mechanism to request/inform the
   egress PCC of the path ID as described in this document.

4.2.  LSP Object

   The LSP Object is defined in Section 7.3 of [RFC8231].  This document
   adds the following flags to the LSP Object:

      P (Path Identification Allocation bit): If the bit is set to 1, it
      indicates that the path identifier needs to be allocated by the
      PCE for this LSP.  A PCC would set this bit to 1 to request for
      allocation of path identifier by the PCE in the PCReq or PCRpt
      message.  A PCE would also set this bit to 1 to indicate that the
      path identifier is allocated by PCE and encoded in the PCRep,
      PCUpd or PCInitiate message (the PATH-ID TLV MUST be present in
      LSP object).  Further, a PCE would set this bit to 0 to indicate
      that the path identifier should be allocated by the PCC as
      described in Section 5.1.1.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                PLSP-ID                | Flag|P|C|  O  |A|R|S|D|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                        TLVs                                 //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 3: P-flag in LSP Object

   The figure is included for the ease of the reader and can be removed
   at the time of publication.

4.2.1.  Path ID TLV

   The PATH-ID TLV is an optional TLV for use in the LSP Object for path
   ID allocation.  The type of this TLV is to be allocated by IANA
   (TBA4).  The format is shown below.











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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Type              |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       IDT     |  Flag     |E|L|            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Path ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                     Figure 4: The PATH-ID TLV Format

   The type (16-bit) of the TLV is TBA4 (to be allocated by IANA).  The
   length (16-bit) has a fixed value of 8 octets.  The value contains
   the following fields:

      IDT (The ID type - 8 bits): The IDT field specifies the type of
      the Path ID field, which carries a Path ID corresponding to the SR
      path.

      *  0: MPLS Path Segment, which is an MPLS label as defined in
         [I-D.cheng-spring-mpls-path-segment].  The PST type MUST be set
         to SR (MPLS).

      *  1: SRv6 Path ID, which is a 4-octet integer as defined in
         [I-D.li-spring-passive-pm-for-srv6-np].  The PST type MUST be
         set to SRv6.

      Flags (8 bits): Two flags are currently defined:

      *  L-Bit (Local/Global - 1 bit): If set, then the Path ID carried
         by the PATH-ID TLV has local significance.  If not set, then
         the Path ID carried by this TLV has global significance (i.e.
         Path ID is global within an SR domain).

      *  E-bit (Egress/Ingress - 1 bit): If set, then the Path ID
         carried by the PATH-ID TLV is allocated from the Egress Path ID
         space.  If not set, then the Path ID carried by this TLV is
         allocated from the Ingress Path ID space.

      *  The unassigned bits MUST be set to 0 and MUST be ignored at
         receipt.

      Reserved (16 bits): MUST be set to 0 and MUST be ignored at
      receipt.




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      Path ID (32 bits): The path ID of an SR path.  The path ID type is
      indicated by the ID Type field.  It can be a path segment
      [I-D.cheng-spring-mpls-path-segment] in MPLS label format.  Or it
      can be a 4 octets integer ID as defined in
      [I-D.li-spring-passive-pm-for-srv6-np] or other IDs that can
      identify a path.

   Only one instance of PATH-ID TLV is processed, if more than one PATH-
   ID TLV is included, the first one is processed and others MUST be
   ignored.

   When the path ID allocation is enable, a PATH-ID TLV should be
   included in the LSP object.

   If the label space is maintained by PCC itself, and the path ID is
   allocated by Egress PCC, then the PCE should request the Path ID from
   Egress PCC as described in Section 5.1.1.  In this case, the PCE
   should send a PCUpdate or PCInitiate message to the egress PCC to
   request the path ID.  The P-flag in LSP should be unset in this case.

   If the path ID is allocated by the ingress node, a PATH-ID TLV MUST
   be included in a LSP object (with E-bit unset) in the PCEP message
   from PCC.  The L-flag is set if the path ID has local significance.
   In this case, the P flag in LSP object is set to 0.

   If the PCC requests the path ID to be allocated by the PCE, P flag in
   LSP object is set to 1 and Path ID TLV MAY be skipped.  After the PCE
   has allocated a path ID, it MUST include the PATH-ID TLV in a LSP
   object, the E-bit is set by PCE based on the path ID space from which
   the allocation is made.

   If the PCE allocated the path ID on its own accord, a PATH-ID TLV
   MUST be included in a LSP object, the E-bit is set by PCE based on
   the path ID space from which the allocation is made.

   If a PCEP node does not recognize the PATH-ID TLV, it would behave in
   accordance with [RFC5440] and ignore the TLV.  If a PCEP node
   recognizes the TLV but does not support the TLV, it MUST send PCErr
   with Error-Type = 2 (Capability not supported).

4.3.  FEC Object

   The FEC Object [I-D.zhao-pce-pcep-extension-pce-controller-sr] is
   used to specify the FEC information and MAY be carried within
   PCInitiate or PCRpt message for the PCECC-SR operations.  The PCE
   MUST inform the Path Identification information to the Egress PCC.
   To do this, this document extends the procedures of




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   [I-D.zhao-pce-pcep-extension-pce-controller-sr] by defining a new FEC
   object type for Path.

   FEC Object-Type is TBA6 'Path'.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                           TLV(s)                            //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 5: The path FEC object Format

   One or more following TLV(s) are allowed in the 'path' FEC object -

   o  SYMBOLIC-PATH-NAME TLV: As defined in [RFC8231], it is a human-
      readable string that identifies an LSP in the network.

   o  LSP-IDENTIFIERS TLVs: As defined in [RFC8231], it is optional for
      SR, but could be used to encode the source, destination and other
      identification information for the path.

   o  SPEAKER-ENTITY-ID TLV: As defined in [RFC8232], a unique
      identifier for the PCEP speaker, it is used to identify the
      Ingress PCC.

   Either SYMBOLIC-PATH-NAME TLV or LSP-IDENTIFIERS TLV MUST be
   included.  SPEAKER-ENTITY-ID TLV is optional.  Only one instance of
   each TLV is processed, if more than one TLV of each type is included,
   the first one is processed and others MUST be ignored.

4.4.  CCI Object

   The Central Control Instructions (CCI) Object is used by the PCE to
   specify the forwarding instructions is defined in
   [I-D.zhao-pce-pcep-extension-for-pce-controller].  Further
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] defined a CCI object
   type for SR.

   The Path ID information is encoded directly in the CCI SR object.
   The Path ID TLV as described in the Section 4.2.1, MUST also be
   included in the CCI SR object as the TLV includes additional
   information regarding the path identifier.

   This document adds the following flags to the CCI Object:




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   o  C (PCC Allocation bit): If the bit is set to 1, it indicates that
      the allocation needs to be done by the PCC for this central
      controller instruction.  A PCE set this bit to request the PCC to
      make an allocation from its SR label/ID space.  A PCC would set
      this bit to indicate that it has allocated the CC-ID and report it
      to the PCE.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            CC-ID                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      MT-ID    |    Algorithm  |        Flags      |C|N|E|V|L|O|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                  SID/Label/Index (variable)                 //
   +---------------------------------------------------------------+
   |                                                               |
   //                        Optional TLV                         //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 6: The CCI object for SR

   (Editor's Note - An update is planned for
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] in the next revision
   detailing this procedure, and the above text might move there.)

5.  Operations

   The path ID allocation and encoding is as per the stateful PCE
   operations for segment routing.  The procedures are as per the
   corresponding extensions defined in [I-D.ietf-pce-segment-routing]
   and [I-D.negi-pce-segment-routing-ipv6] (which are further based on
   [RFC8231] and [RFC8281]).  The additional operations for path
   identification are defined in this section.

   To notify (or request) the path ID to the Egress PCC, the procedures
   are as per the PCECC-SR
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] (which is based on
   [I-D.zhao-pce-pcep-extension-for-pce-controller]).  The additional
   operations are defined in this section.

5.1.  PCC Allocated Path ID








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5.1.1.  Egress PCC Allocated Path ID

   As defined in [I-D.cheng-spring-mpls-path-segment], a path segment/ID
   can be allocated by the egress PCC.  In this case, the ID/label space
   may be maintained on the PCC itself.

   On receiving a stateful path computation request with path ID
   allocation request from an ingress PCC, or by initiating or updating
   an LSP with path ID actively, a PCE can request the egress PCC to
   allocate a path ID.  This is needed if the PCE does not control the
   path IDs for the egress PCC or the ID/label space is maintained by
   the egress PCC itself.

   The mechanism of Path ID request and reply may be achieved by using
   PCInitiate and PCUpd message as described in this section.

5.1.1.1.  Using CCI and FEC objects (PCECC)

   The PCE can request the egress to allocate the path ID using the
   PCInitiate message as described in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].  The C flag in the
   CCI object is set to 1 and the CC-ID is set to a special value of
   0x0000 to indicate that the allocation needs to be done by the PCC.
   The PATH-ID TLV is also be included in CCI object along with the FEC
   object identifying the SR-Path.  The egress PCC would allocate the
   path identification and would report to the PCE using the PCRpt
   message as described in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] with the allocated
   path identification in the CC-ID field as well as in the PATH-ID TLV.

   (Editor's Note - An update is planned for
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] in the next revision
   detailing this procedure)

   If the value of CC-ID/Path-ID is 0 and the C flag is set, it
   indicates that the PCE is requesting a path ID for this LSP.  If the
   CC-ID/Path ID is set to a value 'n' and the C flag is set in the CCI
   object, it indicates that the PCE requests a specific value 'n' of
   path ID.  If the path ID is allocated successfully, the egress PCC
   should report the path ID via PCRpt message with the CCI object along
   with the PATH-ID TLV.  Else, it MUST send a PCErr message with Error-
   Type = TBA7 ("Path SID failure") and Error Value = 1 ("Invalid SID").
   If the value of path ID in CCI object is valid, but the PCC is unable
   to allocate the path ID, it MUST send a PCErr message with Error-Type
   = TBA7 ("Path label/SID failure") and Error Value = 2 ("Unable to
   allocate the specified label/SID").





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   Once the PCE receives the PCRpt message with the CCI object, it can
   obtain the Path ID information from the egress PCC and then update
   the path with path ID or reply to the ingress PCC, the path
   information with path ID.

   If the SR-Path is setup the ingress PCC will acknowledge with a PCRpt
   message to the PCE.  In case of error, as described in
   [I-D.ietf-pce-segment-routing], an PCErr message will be sent back to
   the PCE.  The PCE MUST request the withdraw of the path ID allocation
   by sending a PCInitiate message to remove the central controller
   instruction as per [I-D.zhao-pce-pcep-extension-pce-controller-sr].
   When the LSP is deleted or the path ID is removed, the PCE should
   synchronize with the egress PCC.

   If the egress PCC wishes to withdraw or modify a previously reported
   path ID value, it MUST send a PCRpt message without any PATH-ID TLV
   or with the PATH-ID TLV containing the new path ID respectively in
   the CCI object.  The PCE would further trigger the removal of the
   central controller instruction as per
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].

   If a PCE wishes to modify a previously requested path ID value, it
   MUST send a new PCInitiate message with an allocation request CC-ID/
   PATH-ID TLV containing the new path ID value and C flag is set.  The
   PCE should trigger the removal of the older path ID next as per
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].

























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               Ingress                                    Egress
               +-+-+                +-+-+                 +-+-+
               |PCC|                |PCE|                 |PCC|
               +-+-+                +-+-+                 +-+-+
   1) LSP State  | ----  PCRpt ---->  |                     |
      Delegate   |     Delegate=1     |                     |
                 |     P=1            |2) PCE update        |
                 |                    |   the LSP-DB and    |
                 |                    |   request Path ID   |
                 |                    |                     |
                 |                    | --- PCInitiate ---> | Egress
                 |                    |      CC-ID=0        | allocates
                 |                    |      FEC=Path       | a Path-ID
                 |                    |                     | from its
                 |                    | <----- PCRpt ------ | space
                 |                    |       CC-ID=        |
                 |                    |       Path ID       |
                 |                    |                     |
                 |<----  PCUpd ----   |3)Paths update with  |
                 |     PATH-ID TLV    |  Path ID            |
                 |                    |                     |
   4) LSP State  | -----  PCRpt --->  |                     |
      Report     |                    |                     |
                 |                    |                     |

                  Figure 7: Egress PCC Allocated Path ID

5.1.1.2.  Using LSP objects (PCEP-SR)

   The PATH-ID TLV MUST be included in an LSP object in the PCInitiate
   message sent from the PCE to the egress to request path
   identification allocation by the egress PCC.  The P flag in LSP
   object MUST be set to 0.  This PCInitiate message to egress PCC would
   be the similar to the one sent to ingress PCC as per
   [I-D.ietf-pce-segment-routing], but the egress PCC would only
   allocate the path identification and would not trigger the
   initiation/update operation.

   If the value of path ID is 0x0 it indicates that the PCE is
   requesting a path ID for this LSP.  If the Path ID is set to a value
   'n' and the P flag is unset in the LSP object, it indicates that the
   PCE requests a specific value 'n' of path ID.  If the path ID is
   allocated successfully, the egress PCC should report the path ID via
   PCRpt message with PATH-ID TLV in LSP object.  Else, it MUST send a
   PCErr message with Error-Type = TBA7 ("Path SID failure") and Error
   Value = 1 ("Invalid SID").  If the value of path ID is valid, but the
   PCC is unable to allocate the path ID, it MUST send a PCErr message




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   with Error-Type = TBA7 ("Path label/SID failure") and Error Value = 2
   ("Unable to allocate the specified label/SID").

   Once the PCE receives the PCRpt message, it can obtain the Path ID
   information from the egress PCC and then update the path with path ID
   or reply to the ingress PCC, the path information with path ID.

   If the SR-Path is setup the ingress PCC will acknowledge with a PCRpt
   message to the PCE.  In case of error, as described in
   [I-D.ietf-pce-segment-routing], an PCErr message will be sent back to
   the PCE.  The PCE MUST request the withdraw of the path ID allocation
   by sending a PCUpd message to remove the LSP and associated path ID
   by setting the R flag in the SRP object.  When the LSP is deleted or
   the path ID is removed, the PCE should send a PCUpd message to
   synchronize with the egress PCC.

   If the egress PCC wishes to withdraw or modify a previously reported
   path ID value, it MUST send a PCRpt message without any PATH-ID TLV
   or with the PATH-ID TLV containing the new path ID respectively.

   If a PCE wishes to modify a previously requested path ID value, it
   MUST send a PCUpd message with PATH-ID TLV containing the new path ID
   value and P flag is LSP object would be unset.  Absence of the PATH-
   ID TLV in PCUpd message means that the PCE wishes to withdraw the
   path ID.

   If a PCC receives a valid path ID value from a PCE which is different
   than the current path ID, it MUST try to allocate the new value.  If
   the new path ID is successfully allocated, the PCC MUST report the
   new value to the PCE.  Otherwise, it MUST send a PCErr message with
   Error-Type = TBA7 ("Path label/SID failure") and Error Value = 2
   ("Unable to allocate the specified label/SID").



















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               Ingress                                    Egress
               +-+-+                +-+-+                 +-+-+
               |PCC|                |PCE|                 |PCC|
               +-+-+                +-+-+                 +-+-+
   1) LSP State  | ----  PCRpt ---->  |                     |
      Delegate   |     Delegate=1     |                     |
                 |     P=1            |2) PCE update        |
                 |                    |   the LSP-DB and    |
                 |                    |   request Path ID   |
                 |                    |                     |
                 |                    | --- PCInitiate ---> | Egress
                 |                    |      PATH-ID TLV in | allocates
                 |                    |      LSP Object     | a Path-ID
                 |                    |                     | from its
                 |                    | <----- PCRpt ------ | space
                 |                    |       Path ID       |
                 |                    |                     |
                 |<----  PCUpd ----   |3)Paths update with  |
                 |     PATH-ID TLV    |  Path ID            |
                 |                    |                     |
   4) LSP State  | -----  PCRpt --->  |                     |
      Report     |                    |                     |
                 |                    |                     |


                  Figure 8: Egress PCC Allocated Path ID

5.1.2.  Ingress PCC Allocated Path ID

   The Ingress PCC could allocate the Path ID and inform the PCE via the
   PCRpt message as per [RFC8231].  The PATH-ID TLV MUST be included in
   a LSP object in the PCEP message from PCC.  The P flag in LSP object
   is set to 0.  On receiving this report, the PCE updates the
   information in its database.  The active PCE (where the LSP is
   delegated) further informs the egress about the path ID allocated by
   the PCC using the PCInitiate message as described in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].














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                     Ingress                                    Egress
                     +-+-+                +-+-+                 +-+-+
                     |PCC|                |PCE|                 |PCC|
                     +-+-+                +-+-+                 +-+-+
   1) LSP State        | ----  PCRpt ---->  |                     |
      Delegate and     |     Delegate=1     |                     |
      Inform the       |     PATH-ID TLV    |2) PCE update        |
      Path ID alloc    |                    |   the LSP-DB        |
      by PCC           |                    |                     |
                       |3) PCE informs the  | --- PCInitiate ---> |
                       |   Path ID to Egress|     FEC=Path        |
                       |                    |                     |
                       |                    | <-------- PCRpt --- |
                       |                    |                     |


                  Figure 9: Ingress PCC Allocated Path ID

5.2.  PCE Allocated Path ID

5.2.1.  PCE Controlled ID Spaces Advertisement

   For allocating the path IDs to SR paths by the PCEs, the PCE
   controlled ID Spaces MUST be known at PCEs via configurations or any
   other mechanism.  The PCE controlled ID spaces MAY be advertised as
   described in [I-D.li-pce-controlled-id-space].

5.2.2.  Ingress PCC request Path ID to PCE

   The ingress PCC could request the path ID to be allocated by the PCE
   via PCRpt message as per [RFC8231].  The delegate flag (D-flag) MUST
   also be set for this LSP.  Also, the P-flag in the LSP object MUST be
   set.  The PATH-ID TLV MAY be included with Path ID set to 0x0000.  If
   the Path ID is set to a value 'n' and the P flag is set in the LSP
   object, it indicates that the Ingress PCC requests a specific value
   'n' of path ID.

   If the path ID is allocated successfully, the PCE would further
   respond to Ingress PCC with PCUpd message as per [RFC8231] and MUST
   include the PATH-ID TLV in a LSP object.  Else, it MUST send a PCErr
   message with Error-Type = TBA7 ("Path SID failure") and Error Value =
   1 ("Invalid SID").  If the value of path ID is valid, but the PCC is
   unable to allocate the path ID, it MUST send a PCErr message with
   Error-Type = TBA7 ("Path label/SID failure") and Error Value = 2
   ("Unable to allocate the specified label/SID").






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   The active PCE would allocated the path ID as per the PATH-ID flags
   and in case PATH-ID is not included, the PCE MUST act based on the
   local policy.

   The PCE would further inform the egress PCC about the path ID
   allocated by the PCE using the PCInitiate message as described in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].

                     Ingress                                    Egress
                     +-+-+                +-+-+                 +-+-+
                     |PCC|                |PCE|                 |PCC|
                     +-+-+                +-+-+                 +-+-+
   1) LSP State        | ----  PCRpt ---->  |                     |
      Delegate         |     Delegate=1     |                     |
                       |     P=1            |2) PCE update        |
                       |                    |   the LSP-DB and    |
                       |                    |   allocate Path ID  |
                       |<----  PCUpd ----   |3)Paths update with  |
                       |     PATH-ID TLV    |  Path ID            |
                       |                    |                     |
   4) LSP State Report | -----  PCRpt --->  |                     |
                       |                    |                     |
                       |5) PCE informs the  | --- PCInitiate ---> |
                       |   Path ID to Egress|     FEC=Path        |
                       |                    |                     |
                       |                    | <-------- PCRpt --- |
                       |                    |                     |


               Figure 10: Ingress PCC request Path ID to PCE

5.2.3.  PCE allocated Path ID on its own

   The PCE could allocate the path ID on its own accord for a PCE-
   Initiated (or delegated LSP).  The allocated path ID needs to be
   informed to the Ingress and Egress PCC.  The PCE would use the
   PCInitiate message [RFC8281] or PCUpd message [RFC8231] towards the
   Ingress PCC and MUST include the PATH-ID TLV in the LSP object.  The
   PCE would further inform the egress PCC about the path ID allocated
   by the PCE using the PCInitiate message as described in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].










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                     Ingress                                    Egress
                     +-+-+                +-+-+                 +-+-+
                     |PCC|                |PCE|                 |PCC|
                     +-+-+                +-+-+                 +-+-+
                       |                    |                     |
                       | <--PCInitiate---   |1)Initiate LSP with  |
                       |    PATH-ID TLV     |  Path ID            |
                       |                    |                     |
    2)LSP delegation   |---PCRpt, D=1--->   | (Confirm)           |
                       |                    |                     |
                       |3) PCE informs the  | --- PCInitiate ---> |
                       |   Path ID to Egress|     FEC=Path        |
                       |                    |                     |
                       |                    | <-------- PCRpt --- |
                       |                    |                     |


                Figure 11: PCE allocated Path ID on its own

5.3.  Two Label Solution

   [I-D.cheng-spring-mpls-path-segment] describe a Path Segment to
   uniquely identify an SR path in a specific context. (e.g., in the
   context of the egress node or ingress node of an SR path, or within
   an SR domain).  It further describes two solution based on 'one
   label' or 'two labels' solution.  For the latter, two segments
   (Source segment and Path segment) are used to identify an SR path
   where the source segment is a global node segment which can uniquely
   identify a node within the SR domain (it is NOT used for forwarding
   and indicates that a Path segment immediately follows).  The
   combination of Source segment and Path segment uniquely identify an
   SR Path with an SR domain.

   The procedure described in this document allocates and encode the
   Path Segment only.  It is expected that the Egress PCC is aware of
   the Source segment by some other procedures.  These procedures could
   be IGP, PCECC-SR, or some other mechanisms.

6.  Dataplane Considerations

   As described in [I-D.cheng-spring-mpls-path-segment], in an SR-MPLS
   network, when a packet is transmitted along an SR path, the labels in
   the MPLS label stack will be swapped or popped.  So that no label or
   only the last label may be left in the MPLS label stack when the
   packet reaches the egress node.  Thus, the egress node cannot
   determine from which SR path the packet comes.  For this reason it
   introduces the Path Segment (or Path Identifier).




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   Apart from allocation and encoding of the Path Identifier (described
   in this document) for the LSP, it would also be included in the SID/
   Label stack of the LSP (usually for processing by the egress).  To
   support this, the path segment MAY also be a part of SR-ERO as
   prepared by the PCE as per [I-D.ietf-pce-segment-routing].  The PCC
   MAY also include the path segment while preparing the label stack
   based on the local policy and use-case.

7.  IANA Considerations

7.1.  SR PCE Capability Flags

   SR PCE Capability TLV is defined in [I-D.ietf-pce-segment-routing],
   and the registry to manage the Flag field of the SR PCE Capability
   TLV is requested in [I-D.ietf-pce-segment-routing].  IANA is
   requested to make the following allocation in the aforementioned
   registry.

    Bit     Description                                    Reference

   TBA1     Path Identifier Allocation is supported(P)     This document


7.2.  SRv6 PCE Capability Flags

   SRv6 PCE Capability TLV is defined in defined in
   [I-D.negi-pce-segment-routing-ipv6], and the registry to manage the
   Flag field of the SRv6 PCE Capability Flags is requested in
   [I-D.negi-pce-segment-routing-ipv6].  IANA is requested to make the
   following allocation in the aforementioned registry.

    Bit    Description                                    Reference

   TBA2    Path Identifier Allocation is supported(P)     This document


7.3.  New LSP Flag Registry

   [RFC8231] defines the LSP object; per that RFC, IANA created a
   registry to manage the value of the LSP object's Flag field.  IANA
   has allocated a new bit in the "LSP Object Flag Field" subregistry,
   as follows:

    Bit    Description                                Reference

   TBA3    Request for Path Identifier Allocation(P)  This document





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7.4.  New PCEP TLV

   IANA is requested to add the assignment of a new allocation in the
   existing "PCEP TLV Type Indicators" subregistry as follows:

   Value    Description                   Reference

   TBA4     PATH-ID TLV                   This document

7.4.1.  Path ID TLV

   This document requests that a new subregistry named "PATH-ID TLV ID
   Type Field" to be created to manage the value of the ID type field in
   the PATH-ID TLV.

   Value    Description                   Reference

     0      MPLS Label                    This document
     1      SRv6 Path Segment             This document


   Further, this document also requests that a new subregistry named
   "PATH-ID TLV ID Flag Field" to be created to manage the Flag field in
   the PATH-ID TLV.  New values are assigned by Standards Action
   [RFC8126].  Each bit should be tracked with the following qualities:

   o  Bit number (counting from bit 0 as the most significant bit)

   o  Capability description

   o  Defining RFC

   Bit   Description                               Reference

    6    Allocated by Egress Node(E)               This document
    7    Local Signification(L)                    This document


7.5.  New CCI Flag Registry

   CCI object is defined in defined in
   [I-D.zhao-pce-pcep-extension-for-pce-controller], further
   [I-D.zhao-pce-pcep-extension-pce-controller-sr] defined a CCI object
   type for SR. and the subregistry to manage the Flag field of the CCI
   object for SR is requested in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].  IANA is requested
   to make the following allocation in the aforementioned subregistry.




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    Bit    Description                              Reference

   TBA5    PCC is requested to                      This document
           allocate resource(C)


7.6.  New FEC Type Registry

   A new PCEP object called FEC is defined in
   [I-D.zhao-pce-pcep-extension-pce-controller-sr].  IANA is requested
   to allocate a new Object-Type for FEC object in the "PCEP Objects"
   subregistry.

   Value    Description                   Reference

    TBA6    SR path                       This document


7.7.  PCEP Error Type and Value

   IANA is requested to allocate code-points in the "PCEP-ERROR Object
   Error Types and Values" subregistry for the following new error-types
   and error-values:

   Error-Type   Meaning                     Reference

   TBA7         Path SID failure:           This document
                Error-value = 1
                Invalid SID

                Error-value = 2
                Unable to allocate
                Path SID

8.  Security Considerations

   TBA

9.  Acknowledgments

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.



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   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8232]  Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
              and D. Dhody, "Optimizations of Label Switched Path State
              Synchronization Procedures for a Stateful PCE", RFC 8232,
              DOI 10.17487/RFC8232, September 2017,
              <https://www.rfc-editor.org/info/rfc8232>.

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "PCEP Extensions for Segment Routing",
              draft-ietf-pce-segment-routing-12 (work in progress), June
              2018.

   [I-D.negi-pce-segment-routing-ipv6]
              Negi, M., Kaladharan, P., Dhody, D., and S. Sivabalan,
              "PCEP Extensions for Segment Routing leveraging the IPv6
              data plane", draft-negi-pce-segment-routing-ipv6-02 (work
              in progress), June 2018.








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   [I-D.zhao-pce-pcep-extension-pce-controller-sr]
              Zhao, Q., Li, Z., Dhody, D., Karunanithi, S., Farrel, A.,
              and C. Zhou, "PCEP Procedures and Protocol Extensions for
              Using PCE as a Central Controller (PCECC) of SR-LSPs",
              draft-zhao-pce-pcep-extension-pce-controller-sr-03 (work
              in progress), June 2018.

   [I-D.zhao-pce-pcep-extension-for-pce-controller]
              Zhao, Q., Li, Z., Dhody, D., Karunanithi, S., Farrel, A.,
              and C. Zhou, "PCEP Procedures and Protocol Extensions for
              Using PCE as a Central Controller (PCECC) of LSPs", draft-
              zhao-pce-pcep-extension-for-pce-controller-08 (work in
              progress), June 2018.

10.2.  Informative References

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC4657]  Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol Generic
              Requirements", RFC 4657, DOI 10.17487/RFC4657, September
              2006, <https://www.rfc-editor.org/info/rfc4657>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [I-D.li-pce-controlled-id-space]
              Li, C., Chen, M., Dong, J., Li, Z., and D. Dhody, "PCE
              Controlled ID Space", draft-li-pce-controlled-id-space-00
              (work in progress), June 2018.

   [I-D.cheng-spring-mpls-path-segment]
              Cheng, W., Wang, L., Li, H., Chen, M., Zigler, R., Zhan,
              S., and R. Gandhi, "Path Segment in MPLS Based Segment
              Routing Network", draft-cheng-spring-mpls-path-segment-02
              (work in progress), July 2018.

   [I-D.li-spring-passive-pm-for-srv6-np]
              Li, C. and M. Chen, "Passive Performance Measurement for
              SRv6 Network Programming", draft-li-spring-passive-pm-for-
              srv6-np-00 (work in progress), March 2018.





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Authors' Addresses

   Cheng Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: chengli13@huawei.com


   Mach(Guoyi) Chen
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: Mach.chen@huawei.com


   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: dhruv.ietf@gmail.com


   Weiqiang Cheng
   China Mobile
   China

   Email: chengweiqiang@chinamobile.com


   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: jie.dong@huawei.com








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   Zhenbin Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com


   Rakesh Gandhi
   Cisco Systems, Inc.
   Canada

   Email: rgandhi@cisco.com





































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