[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00

PCE WG                                                           R. Chen
Internet-Draft                                                   ch. Zhu
Intended status: Standards Track                                   B. Xu
Expires: March 29, 2021                                  ZTE Corporation
                                                      September 25, 2020


   PCEP Procedures and Protocol Extensions for Using PCE as a Central
                       Controller (PCECC) of BIER
          draft-chen-pce-pcep-extension-pce-controller-bier-00

Abstract

   This draft specify the procedures and PCEP protocol extensions for
   using the PCE as the central controller for BIER.

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 29, 2021.

Copyright Notice

   Copyright (c) 2020 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.




Chen, et al.             Expires March 29, 2021                 [Page 1]


Internet-Draft                 PCECC BIER                 September 2020


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  PCECC BIER Requirements . . . . . . . . . . . . . . . . . . .   3
   4.  Procedures for Using the PCE as the Central Controller
       (PCECC) in BIER . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Stateful PCE Model  . . . . . . . . . . . . . . . . . . .   3
     4.2.  New Functions . . . . . . . . . . . . . . . . . . . . . .   4
     4.3.  PCECC Capability Advertisement  . . . . . . . . . . . . .   4
     4.4.  BIER Path Operations  . . . . . . . . . . . . . . . . . .   4
       4.4.1.  PCECC Bit Index Explicit Replication (BIER) . . . . .   4
         4.4.1.1.  PCECC BIER information allocation . . . . . . . .   5
         4.4.1.2.  Redundant PCEs  . . . . . . . . . . . . . . . . .   5
         4.4.1.3.  Re Delegation and Cleanup . . . . . . . . . . . .   5
         4.4.1.4.  Synchronization of BIER information Allocations .   5
     4.5.  PCEP messages . . . . . . . . . . . . . . . . . . . . . .   5
       4.5.1.  The OPEN Object . . . . . . . . . . . . . . . . . . .   5
         4.5.1.1.  PCECC Capability sub-TLV  . . . . . . . . . . . .   5
       4.5.2.  PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . .   6
       4.5.3.  CCI object  . . . . . . . . . . . . . . . . . . . . .   6
         4.5.3.1.  BIER Encapsulation Sub TLV  . . . . . . . . . . .   7
       4.5.4.  FEC Object  . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  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.

   [I-D.ietf-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.  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.



Chen, et al.             Expires March 29, 2021                 [Page 2]


Internet-Draft                 PCECC BIER                 September 2020


   [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.

   This document specifies the procedures and PCEP protocol extensions
   when a PCE-based controller is also responsible for configuring the
   forwarding actions on the routers (BIER information distribution in
   this case).

2.  Conventions used in this document

   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.

3.  PCECC BIER Requirements

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

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

   o  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.

   o  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.

   o  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.

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

4.1.  Stateful PCE Model

   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.



Chen, et al.             Expires March 29, 2021                 [Page 3]


Internet-Draft                 PCECC BIER                 September 2020


4.2.  New Functions

   This document uses the same PCEP messages and its extensions which
   are described in [I-D.ietf-pce-pcep-extension-for-pce-controller]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
   [I-D.ietf-pce-pcep-extension-for-pce-controller] is used to download
   or cleanup central controller's instructions (CCIs) (BIER related
   informations in scope of this document).  The extended PCRpt message
   described in [I-D.ietf-pce-pcep-extension-for-pce-controller] is also
   used to report the CCIs (BIER related informations) from PCC to PCE.

   [I-D.ietf-pce-pcep-extension-for-pce-controller]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.

4.3.  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
   [I-D.ietf-pce-pcep-extension-for-pce-controller].

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

4.4.  BIER Path Operations

   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 LSP is intended.

4.4.1.  PCECC Bit Index Explicit Replication (BIER)

   BIER as described in [RFC8402] defines an architecture where all
   intended multicast receivers are encoded as a bitmask in the
   multicast packet header within different encapsulations such as
   described in [RFC8296].

   [RFC8401] defines IS-IS extensions to distribute the BIER
   information(BIER subdomain-id, BFR-id and BSL etc).This document
   proposes a new mechanism where PCE allocates centrally and uses PCEP
   to advertise the BIER information(BIER subdomain-id, BFR-id and BSL
   etc).  In some deployments PCE (and PCEP) are better suited than IGP
   because of centralized nature of PCE and direct TCP based PCEP
   session to the node.



Chen, et al.             Expires March 29, 2021                 [Page 4]


Internet-Draft                 PCECC BIER                 September 2020


4.4.1.1.  PCECC BIER information allocation

   Each node (PCC) is allocated BIER information by the PCECC.The BIER
   information mainly includes BIER subdomain-id, BFR-id, BSL, BFR
   prefix, BSL, Encapsulation Type, BIFT ID,Max SI and BFR nexthop.

   The PCECC allocate the BIER subdomain-id, BFR-id , BFR prefix, BSL,
   Encapsulation Type, BIFT ID, and Max SI to the PCC, On receiving the
   BIER information allocation, each node (PCC) uses IGP protocol to
   distribute BIER related information to other nodes.  The node
   calculate the nexthop.

4.4.1.2.  Redundant PCEs

   [I-D.litkowski-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.

4.4.1.3.  Re Delegation and Cleanup

   [I-D.ietf-pce-pcep-extension-for-pce-controller] 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.

4.4.1.4.  Synchronization of BIER information Allocations

   [I-D.ietf-pce-pcep-extension-for-pce-controller]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 information as well.

4.5.  PCEP messages

4.5.1.  The OPEN Object

4.5.1.1.  PCECC Capability sub-TLV

   [I-D.ietf-pce-pcep-extension-for-pce-controller] defined the
   PCECCCAPABILITY TLV.  A new B-bit is defined in PCECC-CAPABILITY sub-
   TLV for PCECC-BIER:









Chen, et al.             Expires March 29, 2021                 [Page 5]


Internet-Draft                 PCECC BIER                 September 2020


     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

   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.

4.5.2.  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 were
   allocated/instructed by PCE via PCECC mechanism.

4.5.3.  CCI object

   The Central Control Instructions (CCI) Object is used by the PCE to
   specify the forwarding instructions is defined in
   [I-D.ietf-pce-pcep-extension-for-pce-controller].  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  |   Algorithm   |           Flags           |C|O|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           BFR-ID              |        Reserved               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //                       Optional TLV                          //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2




Chen, et al.             Expires March 29, 2021                 [Page 6]


Internet-Draft                 PCECC BIER                 September 2020


   The field CC-ID is as described in
   [I-D.ietf-pce-pcep-extension-for-pce-controller].

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

   The 0 and C bit was defined in
   [I-D.ietf-pce-pcep-extension-for-pce-controller].

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

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

4.5.3.1.  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            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Flage             | ET|             Reserved          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Max SI      |BS Len |                  BIFT-id              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 3

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

   Length:4

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

   o  0b00-MPLS encapsulation.

   o  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].





Chen, et al.             Expires March 29, 2021                 [Page 7]


Internet-Draft                 PCECC BIER                 September 2020


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

4.5.4.  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 [I-D.zhao-pce-pcep-extension-pce-controller-sr] to carry
   the BFR prefix.

5.  Security Considerations

   TBD.

6.  IANA Considerations

   TBD.

7.  Contributors

   The following author contributed significantly to this document:

      Dhruv Dhody

      Huawei

      rdhruv.ietf@gmail.com

8.  Acknowledgements

   TBD.

9.  Normative References

   [I-D.ietf-pce-pcep-extension-for-pce-controller]
              Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP
              Procedures and Protocol Extensions for Using PCE as a
              Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep-
              extension-for-pce-controller-07 (work in progress),
              September 2020.

   [I-D.litkowski-pce-state-sync]
              Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter
              Stateful Path Computation Element (PCE) Communication
              Procedures.", draft-litkowski-pce-state-sync-08 (work in
              progress), July 2020.





Chen, et al.             Expires March 29, 2021                 [Page 8]


Internet-Draft                 PCECC BIER                 September 2020


   [I-D.zhao-pce-pcep-extension-pce-controller-sr]
              Li, Z., Peng, S., Negi, M., Zhao, Q., 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-07 (work in progress),
              July 2020.

   [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>.

   [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>.

   [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>.





Chen, et al.             Expires March 29, 2021                 [Page 9]


Internet-Draft                 PCECC BIER                 September 2020


   [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>.

Authors' Addresses

   Ran Chen
   ZTE Corporation

   Email: chen.ran@zte.com.cn


   Chun Zhu
   ZTE Corporation

   Email: zhu.chun@zte.com.cn


   BenChong Xu
   ZTE Corporation

   Email: xu.benchong@zte.com.cn




























Chen, et al.             Expires March 29, 2021                [Page 10]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/