PCE Working Group                                                M. Wang
Internet-Draft                                                    L. Han
Intended status: Informational                              China Mobile
Expires: 26 September 2022                                      M. Huang
                                                                  Z. Han
                                                                  J. Dai
                                                                    CICT
                                                           25 March 2022


                PCEP Extension for INTERACTING-CAPBILITY
                 draft-whh-pce-capability-advertize-00

Abstract

   The PCE communication Protocol (PCEP) is used to convey path
   computation requests and responses both between Path Computation
   Clients (PCCs), Path Computation Elements (PCEs) and cooperating
   PCEs, support of traffic engineering in Multiprotocol Label Switching
   (MPLS), Generalized MPLS (GMPLS) and Segment Routing (SR) networks.
   In PCEP, due to the different implementing of PCC tunnel capability,
   especially bidirectional SR tunnels, the PCE can only provides path
   computation functions between the PCCs which adopt identical
   mechanisms.

   With the introduction and evolvement of 5G and other network
   scenarios, the scale of bearing and transport network has developed
   to a high level.  On the other hand, with the improvement of network
   slicing ability, network equipments can provide network slicing
   service, such as enhanced VPNs (VPN+).  Transport network employing
   time slot isolation technology, such as FlexE,MTN,can provide
   advanced timeslot slicing for the high quality customer services.
   The high quality customer services, for example industry production
   service, demand for superior SLA and end-to-end timeslot service
   slicing, regardless of whether it is across of different network
   equipment providers or across of different regions.  Therefore, there
   is an urgent need of a method to support PCE to provide end-to-end
   path computation and establishment of SR tunnels regardless of PCC
   enables different protocol selections.

   This document specifies the extensions to PCE communication Protocol
   (PCEP) to carry bidirectional SR tunnel capability advertisement
   information in PCEP message to enhance PCE ability to perceive the
   protocol mechanism supported by PCC.

Requirements Language





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   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.

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 26 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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview of SR Tunnel Capability Notification in PCEP . . . .   4
   4.  TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8



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   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [RFC5440]describes the Path Computation Element (PCE) Communication
   Protocol (PCEP).  PCEP defines the communication between a Path
   Computation Client (PCC) and a PCE, or between PCE and PCE, enabling
   computation of Multiprotocol Label Switching (MPLS) for 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.ietf-pce-segment-routing] specifies extensions to the Path
   Computation Element Protocol (PCEP)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.li-pce-sr-path-segment] specifies a mechanism to carry the SR
   path identification information in PCEP messages.

   [I-D.ietf-pce-binding-label-sid] specifies the binding value as an
   MPLS label or Segment Identifier.  It further specifies an approach
   for reporting binding label/Segment Identifier (SID) by a Path
   Computation Client (PCC) to the Path Computation Element (PCE) to
   support PCE-based Traffic Engineering policies.

   Two different implementation mechanisms of PCEP are defined in the
   standard protocol: Passive Stateful PCE and Active Stateful PCE.  For
   Passive Stateful PCE, the PCC sends a path computation request to the
   PCE, the PCE triggers a path computation and returns either a
   positive or a negative reply to the PCC.  For Active Stateful PCE, to
   create or update LSP, PCE MUST send LSP Update Request to PCC using
   PCUpd message or using PCInt message.

   [I-D.li-pce-sr-path-segment] specifies various modes of operations
   for SR-path segment.  Path Segment can be either allocated by Egress
   PCC or PCE.  This leads to different implementation methods for the
   extension of Path Segment.  Meanwhile PCEP procedure is divided into
   PCC-initiated and PCE-initiated LSPs[RFC9059].For example,
   Association ID is used for bidirectional SR tunnel binding.  The
   difference of Association ID allocation between PCC-initiated and
   PCE-initiated is as follows: In PCC-initiated, the PCE needs to



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   control whether the PCC reports the Association ID or not.  If the
   PCE receives the Association ID reported by the PCC through PCRpt, it
   will be issued according to the Association ID reported by the PCC;
   if the PCE has not received the Association ID through the PCC, the
   PCE will directly assign an ID to the PCC.  In PCE-initiated,the PCE
   directly assigns the AssociationID.

   This document specifies a new OPTIONAL TLV for multiple PCC
   interworking scenarios.  PCC can employ this TLV to report PCC
   abilities of supporting different mechanisms of bidirectional SR
   tunnels.  PCE can perceive the specific implementation mode of PCC by
   parsing this TLV,in order to achieve the compatibility of multiple
   sets of PCEP standard processes in the management and control system.
   Particularly, Vendor TLV[RFC7470] can be used as a special
   implementation mechanism when various capability distinctions have
   been reconciled in advance.


2.  Terminology

   This memo makes use of the terms defined in [RFC4655],
   [RFC5440],[I-D.li-pce-sr-path-segment],
   [I-D.ietf-pce-binding-label-sid] and [RFC8042].


3.  Overview of SR Tunnel Capability Notification in PCEP

   SR-PCE-INTERACTING-CAPBILITY TLV clarifies various capability
   distinctions of PCC.  Through this TLV,the PCC sends its own
   capability information to the PCE,which is used to determine the
   bidirectional segment routing tunnel capability supported by the PCC,
   whether the tunnel creation is initiated by the PCC or the PCE, and
   whether the distribution is supported by the label allocation to the
   PCC or the PCE,etc.

   The PCE determines the bidirectional SR tunnel capability supported
   by the PCC through the acquired capability information of the PCC,
   and performs corresponding management on the PCC that supports
   different capabilities according to the capability.  The PCE parses
   this TLV.  Through the analysis results of different fields in this
   tlv, it can preceive which mode of the PCEP standard process is
   currently supported by PCC,in order to achieve PCEP interoperability.
   This solution can realize the PCEP implementation to compatible with
   different PCCs.







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4.  TLV

   The SR-PCE-INTERACTING-CAPBILITY is an optional TLV associated with
   the OPEN Object to exchange SR Tunnel Capability Notification of PCEP
   speakers.  When the PCEP session is created, PCC sends an Open
   message with an OPEN object containing the SR-PCE-INTERACTING-
   CAPBILITY TLV.

   When the PCE receives the Open message with a SR-PCE-INTERACTING-
   CAPBILITY TLV, the PCE can parse the TLV.  According to the results
   of the analysis of each capability field of the TLV, it can realize
   how the PCC implements the SR tunnel as a basis to send the
   corresponding PCEP message.  In an Open message, a PCC MAY insert one
   SR-PCE-INTERACTING-CAPBILITY-TLV, PCC can assign different values to
   the corresponding fields to announce its own PCEP capability.

   The format of SR-PCE-INTERACTING-CAPBILITY TLV is defined as follows:


       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 = TDB            |       Length = 4          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Reserved                |     N   |FLAGS|S|C|P|B|T|A|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1 SR-PCE-INTERACTING-CAPBILITY TLV format

   The code point for the TLV type is to be defined by IANA.  The TLV
   length is 4 octets.

   The 32-bit value is formatted as follows.  The "Reserved" is unused.

   The" Flags "(2 bits) field is unused, and MUST be set to zero on
   transmission and ignored on reception.  This document defines the
   following flag:

   o N(Number of PCInt messages sent when creating a tunnel-8 bits):
   This field indicates the number of times that PCInt messages need to
   be sent to create a tunnel.  If set to 1 by a PCC means sending it
   once, If set to 2 by a PCC means sending it twice, and supports
   expansion.

   o S (SR tunnel initiator-1 bit): This field is used to distinguish
   the tunnel initiator.  If set to 1 by a PCC means that the PCC
   initiates the tunnel request.  If set to 0 by a PCC means that the
   PCE sends the tunnel information.



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   o C (Configuration tunnel-1bit): This field is used to indicate
   whether the PCE is configured with a tunnel.  If set to 1 by a PCC,
   the PCE configures the tunnel.  If set to 0 by a PCC, the PCE does
   not configure the tunnel.

   o P (Path Segment label assignment-1 bit): This field is used to
   indicate Path Segment label allocation.  If set to 1 by a PCC, the
   Path Segment label is allocated by PCC, If set to 0 by a PCC, the
   Path Segment label is allocated by PCE.

   o B (Binding label-1bit): This field is used to indicate the
   allocation of the adhesive label.  If set to 1 by a PCC, the Binding
   label is allocated by the PCC, If set to 1 by a PCC, the Binding
   label is allocated by the PCE.

   o T (Time sequence dependency-1bit): This field indicates whether
   there is a timing dependency in the protocol interaction.  If set to
   1 by a PCC, it means that there is a strong dependence between PCEP
   message interaction and time sequence.  If set to 0 by a PCC, it
   means that there is no timing dependency.

   o A (Association ID 1bit): This field indicates the assignment of the
   Association ID.  If set to 1 by a PCC, it means that the Association
   ID is allocated by PCC.  If set to 0 by a PCC, it means that the
   association id is allocated by PCE.

5.  IANA Considerations

   IANA is requested to make allocations from the registry, as follows:


         +======+==============================+=================+
        | Type |            TLV               |    Reference    |
        +======+==============================+=================+
        | TBD1 | SR-PCE-INTERACTING-CAPBILITY | [this document] |
        +------+------------------------------+-----------------+

6.  Security Considerations

   TBD

7.  References

7.1.  Normative References







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   [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>.

   [RFC4657]  Ash, J., Ed. and J.L. 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>.

   [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>.

   [RFC7470]  Zhang, F. and A. Farrel, "Conveying Vendor-Specific
              Constraints in the Path Computation Element Communication
              Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015,
              <https://www.rfc-editor.org/info/rfc7470>.

   [RFC8042]  Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part
              Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,
              <https://www.rfc-editor.org/info/rfc8042>.

   [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>.

   [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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   [RFC9059]  Gandhi, R., Ed., Barth, C., and B. Wen, "Path Computation
              Element Communication Protocol (PCEP) Extensions for
              Associated Bidirectional Label Switched Paths (LSPs)",
              RFC 9059, DOI 10.17487/RFC9059, June 2021,
              <https://www.rfc-editor.org/info/rfc9059>.

7.2.  Informative References

   [I-D.ietf-pce-binding-label-sid]
              Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S.,
              and C. L. (editor), "Carrying Binding Label/Segment
              Identifier (SID) in PCE-based Networks.", Work in
              Progress, Internet-Draft, draft-ietf-pce-binding-label-
              sid-15, 20 March 2022, <https://www.ietf.org/archive/id/
              draft-ietf-pce-binding-label-sid-15.txt>.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "Path Computation Element Communication
              Protocol (PCEP) Extensions for Segment Routing", Work in
              Progress, Internet-Draft, draft-ietf-pce-segment-routing-
              16, 4 March 2019, <https://www.ietf.org/archive/id/draft-
              ietf-pce-segment-routing-16.txt>.

   [I-D.li-pce-sr-path-segment]
              Li, C., Chen, M., Cheng, W., Dong, J., Li, Z., Gandhi, R.,
              and Q. Xiong, "Path Computation Element Communication
              Protocol (PCEP) Extension for Path Segment in Segment
              Routing (SR)", Work in Progress, Internet-Draft, draft-li-
              pce-sr-path-segment-08, 19 August 2019,
              <https://www.ietf.org/archive/id/draft-li-pce-sr-path-
              segment-08.txt>.

Authors' Addresses

   Minxue Wang
   China Mobile
   Beijing
   China
   Email: wangminxue@chinamobile.com


   Liuyan Han
   China Mobile
   Beijing
   China
   Email: hanliuyan@chinamobile.com




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   Mianzhang Huang
   CICT
   Wuhan
   China
   Email: mzhuang@fiberhome.com


   Zhen Han
   CICT
   Wuhan
   China
   Email: zhhan@fiberhome.com


   Jinyou Dai
   CICT
   Wuhan
   China
   Email: djy@fiberhome.com
































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