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Versions: 00 01 02 03                                                   
PCE                                                              R. Chen
Internet-Draft                                                   ch. Zhu
Intended status: Standards Track                                   B. Xu
Expires: 7 September 2022                                ZTE Corporation
                                                                 H. Chen
                                                               Futurewei
                                                                 A. Wang
                                                           China Telecom
                                                            6 March 2022


   PCEP Procedures and Protocol Extensions for Using PCE as a Central
                       Controller (PCECC) of BIER
          draft-chen-pce-pcep-extension-pce-controller-bier-03

Abstract

   This draft specify a new mechanism where PCE allocates the BIER
   information centrally and uses PCEP to distribute them to all nodes,
   then PCC generate a "Bit Index Forwarding Table"(BIFT).

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 7 September 2022.

Copyright Notice

   Copyright (c) 2022 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



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   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  PCECC BIER Requirements . . . . . . . . . . . . . . . . . . .   3
   3.  Procedures for Using the PCE as the Central Controller (PCECC)
           in BIER . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  PCECC Capability Advertisement  . . . . . . . . . . . . .   4
     3.2.  New BIER Path Setup . . . . . . . . . . . . . . . . . . .   4
     3.3.  PCECC BIER information allocation and Generation of
           BFIT  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.4.  Redundant PCEs  . . . . . . . . . . . . . . . . . . . . .   5
     3.5.  Re Delegation and Cleanup . . . . . . . . . . . . . . . .   5
     3.6.  Synchronization of BIER information Allocations . . . . .   5
   4.  PCEP extension  . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  The OPEN Object . . . . . . . . . . . . . . . . . . . . .   5
       4.1.1.  PCECC Capability sub-TLV  . . . . . . . . . . . . . .   5
     4.2.  PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . .   6
     4.3.  CCI object  . . . . . . . . . . . . . . . . . . . . . . .   6
       4.3.1.  BIER Encapsulation Sub TLV  . . . . . . . . . . . . .   7
       4.3.2.  Address TLVs  . . . . . . . . . . . . . . . . . . . .   8
     4.4.  FEC Object  . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   [RFC8283]introduces the architecture for PCE as a central controller
   as an extension of the architecture described in [RFC4655] and
   assumes the continued use of PCEP as the protocol used between PCE
   and PCC.  [RFC8283]further examines the motivations and applicability
   for PCEP as a Southbound Interface (SBI), and introduces the
   implications for the protocol.











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   [RFC9050] 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.  Each router along the path must be told what label-
   forwarding instructions to program and what resources to reserve.
   The PCE-based controller keeps a view of the network and determines
   the paths of the end-to-end LSPs, and the controller uses PCEP to
   communicate with each router along the path of the end-to-end LSP.

   [RFC8279] defines a Bit Index Explicit Replication (BIER)
   architecture where all intended multicast receivers are encoded as a
   bitmask in the multicast packet header within different
   encapsulations such as described in [RFC8296].  A router that
   receives such a packet will forward the packet based on the bit
   position in the packet header towards the receiver(s) following a
   precomputed tree for each of the bits in the packet.  Each receiver
   is represented by a unique bit in the bitmask.

   In order to reduce the transmission of redundant information, the
   PCE-based controllers do not allocate the BFIT directly.  Instead,
   the PCC generates the BFIT based on the received bier informations or
   the node calculates the nexthop by itself.  This document specifies
   the procedures and PCEP protocol extensions when a PCE-based
   controller is also responsible for configuring the BIER informations.

1.1.  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 RFC 2119 [RFC2119].

2.  PCECC BIER Requirements

   Following key requirements for PCECC-BIER should be considered
   when`designing the PCECC based solution:

   *  PCEP speaker supporting this draft needs to have the capability to
      advertise its PCECC-BIER capability to its peers.

   *  PCEP speaker not supporting this draft needs to be able to reject
      PCECC-BIER related message with a reason code that indicates no
      support for PCECC.

   *  PCEP procedures needs to provide a means to update (or cleanup)
      the BIER related informations (BIER subdomain-id, BFR-id and BSL
      etc) to the PCC.





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   *  PCEP procedures needs to provide a means to update (or cleanup)
      the "Bit Index Forwarding Table"(BIFT) to the PCC.

   *  PCEP procedures needs to provide a means to synchronize the BIER
      related informations (BIER subdomain-id, BFR-id and BSL etc)
      between PCE to PCC in the PCEP messages.

3.  Procedures for Using the PCE as the Central Controller (PCECC) in
    BIER

   Active stateful PCE is described in [RFC8231].  PCE as a central
   controller (PCECC) reuses existing Active stateful PCE mechanism as
   much as possible to control the LSP.

   This document uses the same PCEP messages and its extensions which
   are described in [RFC9050] for PCECC-BIER as well.

   PCEP messages PCRpt, PCInitiate, PCUpd are also used to send LSP
   Reports, LSP setup and LSP update respectively.  The extended
   PCInitiate message described in [RFC9050] is used to download or
   cleanup central controller's instructions (CCIs) (BIER related
   informations and "Bit Index Forwarding Table"(BIFT) in scope of this
   document).  The extended PCRpt message described in [RFC9050] is also
   used to report the CCIs (BIER related informations) from PCC to PCE.

   [RFC9050] specify an object called CCI for the encoding of central
   controller's instructions.  This document extends the CCI by defining
   another object-type for BIER.

3.1.  PCECC Capability Advertisement

   During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
   advertise their support of PCECC extensions.  A PCEP Speaker includes
   the "PCECC Capability" sub-TLV, described in [RFC9050].

   This document adds B-bit in PCECC-CAPABILITY sub-TLV for BIER.

3.2.  New BIER Path Setup

   The PCEP messages pertaining to PCECC-BIER MUST include PATH-SETUP-
   TYPE TLV [RFC8408] with PST=TBD in the SRP object to clearly identify
   the PCECC-BIER is intended.

3.3.  PCECC BIER information allocation and Generation of BFIT

   There are two ways to generate a "Bit Index Forwarding Table"(BIFT):





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   *  The PCECC allocate parameters(BIER subdomain-id, BFR-id, BAR and
      IPA) carried by CCI object, parameters(BFR prefix, BSL,
      Encapsulation Type, BIFT ID, and Max SI) carried by BIER
      Encapsulation TLV and parameters (BFR prefix)carried by OFEC
      Object to the PCC.  On receiving the BIER informations allocation,
      each node (PCC) uses IGP protocol to distribute BIER related
      information to other nodes.  The node calculate the nexthop.  In
      this case, Each node (PCC) only needs to be allocated its own BIER
      informations by the PCECC.

   *  In scenarios where the IGP protocol is not used/available,Each
      node (PCC) is allocated its own and neighbor BIER informations by
      the PCECC, then PCC generates a BIFT based on the informations it
      receives.  The BIER informations include BIER subdomain-id and
      BFR-id carried by CCI object, BFR prefix, BSL, Encapsulation Type,
      BIFT ID, and Max SI carried by BIER Encapsulation TLV , BFR-NBR
      carried by Address TLV and BFR prefix carried by OFEC Object.  The
      BIFT mainly includes BFR ID, F-BM and BFR nexthop.

3.4.  Redundant PCEs

   [I-D.ietf-pce-state-sync] describes synchronization mechanism between
   the stateful PCEs.  The BIER informations allocated by a PCE MUST
   also be synchronized among PCEs for PCECC BIER state synchronization.

3.5.  Re Delegation and Cleanup

   [RFC9050] describes the action needed for CCIs for the Basic PCECC
   LSP on this terminated session.  Similarly actions should be applied
   for the BIER information as well.

3.6.  Synchronization of BIER information Allocations

   [RFC9050] describes the synchronization of Central Controller's
   Instructions (CCI) via LSP state synchronization as described in
   [RFC8231] and [RFC8232].Same procedures should be applied for BIER
   informations as well.

4.  PCEP extension

4.1.  The OPEN Object

4.1.1.  PCECC Capability sub-TLV

   [RFC9050] defined the PCECC-CAPABILITY TLV.  A new B-bit is defined
   in PCECC-CAPABILITY sub-TLV for PCECC-BIER:





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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=TBD                  |               Length          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Flags                                    |B|I|S|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 1

   where:

   B (PCECC-BIER-CAPABILITY - 1 bit): If set to 1 by a PCEP speaker, it
   indicates that the PCEP speaker is capable for PCECC-BIER capability
   and PCE would allocate BIER information on this session.

4.2.  PATH-SETUP-TYPE TLV

   The PATH-SETUP-TYPE TLV is defined in [RFC8408].  PST = TBD is used
   when Path is setup via PCECC BIER mode.On a PCRpt/PCUpd/PCInitiate
   message, the PST=TBD indicates that this path was setup via a PCECC-
   BIER based mechanism where either the BIER informations and BIER
   forwarding entries were allocated/instructed by PCE via PCECC
   mechanism.

4.3.  CCI object

   The Central Control Instructions (CCI) Object is used by the PCE to
   specify the forwarding instructions is defined in [RFC9050].  This
   document defines another object-type for BIER purpose.

   CCI Object-Type is TBD for BIER as below


     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                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | subdomain-ID  |     BAR       |     IPA       | Flags         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           BFR-ID              |        Reserved               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //                       Optional TLV                          //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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                                  Figure 2

   where:

   The field CC-ID is as described in [RFC9050].

   BIER subdomain-ID: Unique value identifying the BIER subdomain. (as
   defined in [RFC8401].

   BAR:BIER Algorithm, as documented in [RFC8401].  Specifies a BIER-
   specific algorithm used to calculate underlay paths to reach BFERs.
   Values are allocated from the "BIER Algorithms" registry.

   IPA:IGP Algorithm, as documented in [RFC8401].  Specifies an IGP
   Algorithm to either modify, enhance, or replace the calculation of
   underlay paths to reach BFERs as defined by the BAR value.  Values
   are from the IGP Algorithm registry. 1 octet.

   Flags (16 bit): A field used to carry any additional information
   pertaining to the CCI.

   BFR-ID: A 2-octet field encoding the BFR-id, as documented in
   [RFC8279].

   Optional TLV: There are two optional TLV are defined/reused in this
   draft.

4.3.1.  BIER Encapsulation Sub TLV


      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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Flags             | ET|             Reserved          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Max SI      |BS Len |                  BIFT-id              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 3

   where:

   The code point for the TLV type is to be defined by IANA.

   Length:4




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   ET-Flag:ET(Encapsulation type) Flag,There are two Encapsulation
   Types:

   *  0b00-MPLS encapsulation.

   *  0b01-Non-MPLS encapsulation.

   Max SI: A 1 octet field encoding the Maximum Set Identifier(Section 1
   of [RFC8279] ) used in the encapsulation for this BIER subdomain for
   this BitString length.

   Local BitString Length (BS Len): Encoded BitString length as per
   [RFC8296].

   BIFT-id: A 20 bit field encoding the first BIFT-id of the BIFT-id
   range.

4.3.2.  Address TLVs

   Address TLVs described in [RFC9050] are used to associate the next-
   hop information, so we Reuse ADDRESS TLV to carry the BFR out-
   interface and nexthop informations.

4.4.  FEC Object

   BIER information is always associated with a host prefix, so we reuse
   FEC Object 1'IPv4 Node ID' and FEC Object-Type 2 'IPv6 Node ID'
   defined in [RFC8664] to carry the BFR prefix.

5.  Acknowledgements

   We would like to thank Dhruv Dhody for their useful comments and
   suggestions.

6.  IANA Considerations

   TBD.

7.  Security Considerations

   The PCECC extension are based on the existing PCEP messages and thus
   the security considerations described in

   The PCECC extension are based on the existing PCEP messages and thus
   the security considerations described in [RFC5440] ,[RFC8231]
   ,[RFC8281], and [RFC9050] apply to this draft.

8.  Normative References



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   [I-D.ietf-pce-state-sync]
              Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter
              Stateful Path Computation Element (PCE) Communication
              Procedures.", Work in Progress, Internet-Draft, draft-
              ietf-pce-state-sync-01, 20 October 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-pce-
              state-sync-01>.

   [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>.

   [RFC4655]  Farrel, A., Vasseur, J.-P., 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>.

   [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>.

   [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>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

   [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>.





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   [RFC8283]  Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
              Architecture for Use of PCE and the PCE Communication
              Protocol (PCEP) in a Network with Central Control",
              RFC 8283, DOI 10.17487/RFC8283, December 2017,
              <https://www.rfc-editor.org/info/rfc8283>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

   [RFC8401]  Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
              Zhang, "Bit Index Explicit Replication (BIER) Support via
              IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
              <https://www.rfc-editor.org/info/rfc8401>.

   [RFC8408]  Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
              Hardwick, "Conveying Path Setup Type in PCE Communication
              Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
              July 2018, <https://www.rfc-editor.org/info/rfc8408>.

   [RFC8664]  Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "Path Computation Element Communication
              Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
              DOI 10.17487/RFC8664, December 2019,
              <https://www.rfc-editor.org/info/rfc8664>.

   [RFC9050]  Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "Path
              Computation Element Communication Protocol (PCEP)
              Procedures and Extensions for Using the PCE as a Central
              Controller (PCECC) of LSPs", RFC 9050,
              DOI 10.17487/RFC9050, July 2021,
              <https://www.rfc-editor.org/info/rfc9050>.

Authors' Addresses

   Ran Chen
   ZTE Corporation
   Nanjing
   China
   Email: chen.ran@zte.com.cn


   Chun Zhu
   ZTE Corporation
   Nanjing
   China



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   Email: zhu.chun@zte.com.cn


   BenChong Xu
   ZTE Corporation
   Nanjing
   China
   Email: xu.benchong@zte.com.cn


   Huaimo Chen
   Futurewei
   Nanjing,
   United States of America
   Email: Huaimo.chen@futurewei.com


   Aijun Wang
   China Telecom
   Nanjing
   China
   Email: wangaj3@chinatelecom.cn





























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