



PCE                                                             Q. Xiong
Internet-Draft                                           ZTE Corporation
Intended status: Standards Track                         23 October 2022
Expires: 26 April 2023


    Label Switched Path (LSP) Object Flag Extension for Stateful PCE
                  draft-ietf-pce-lsp-extended-flags-09

Abstract

   RFC 8231 describes a set of extensions to Path Computation Element
   Communication Protocol (PCEP) to enable stateful control of MPLS-TE
   and GMPLS Label Switched Paths (LSPs) via PCEP.  One of the
   extensions is the LSP object which includes a Flag field with a
   length of 12 bits.  However, all bits of the Flag field have already
   been assigned in RFC 8231, RFC 8281, RFC 8623 and I-D.ietf-pce-
   binding-label-sid.

   [Note to RFC Editor - Replace I-D.ietf-pce-binding-label-sid to RFC
   XXXX, once the RFC number is assigned.]

   This document proposes to define a new LSP-EXTENDED-FLAG TLV for the
   LSP object for an extended flag field.

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 April 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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 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
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  PCEP Extension  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  The LSP-EXTENDED-FLAG TLV . . . . . . . . . . . . . . . .   3
     3.2.  Processing  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Advice for Specification of New Flags . . . . . . . . . . . .   5
   5.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  LSP Object  . . . . . . . . . . . . . . . . . . . . . . .   5
       6.1.1.  PCEP TLV Type Indicators  . . . . . . . . . . . . . .   5
       6.1.2.  LSP Extended Flags Field  . . . . . . . . . . . . . .   6
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .   6
   8.  Management Considerations . . . . . . . . . . . . . . . . . .   7
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   7
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     12.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     12.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Appendix A.  WG Discussion  . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   [RFC5440] describes the Path Computation Element (PCE) Communication
   Protocol (PCEP) which is used between a PCE and a Path Computation
   Client (PCC) (or other PCE) to enable computation of Multi-protocol
   Label Switching for Traffic Engineering (MPLS-TE) Label Switched Path
   (LSP).

   PCEP Extensions for the Stateful PCE Model [RFC8231] describes a set
   of extensions to PCEP to enable active control of MPLS-TE and
   Generalized MPLS (GMPLS) tunnels.  One of the extensions is the LSP
   object, which contains a flag field; bits in the flag field are used
   to indicate delegation, synchronization, removal, etc.



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   As defined in [RFC8231], the length of the flag field is 12 bits and
   the values from bit 5 to bit 11 are used for operational,
   administrative, remove, synchronize and delegate bits respectively.
   The bit value 4 is assigned in [RFC8281] to identify the PCE-
   Initiated LSPs.  The bits from 1 to 3 are assigned in [RFC8623] for
   Explicit Route Object (ERO)-compression, fragmentation and Point-to-
   Multipoint (P2MP) respectively.  The bit 0 is assigned in
   [I-D.ietf-pce-binding-label-sid] to PCE-allocation.  All bits of the
   Flag field have been assigned already.  This document extends the
   flag field of the LSP Object for other use.

   This document proposes to define a new LSP-EXTENDED-FLAG TLV for an
   extended flag field in the LSP object.

2.  Conventions used in this document

2.1.  Terminology

   The terminology is defined as [RFC5440] and [RFC8231].

2.2.  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.

3.  PCEP Extension

   The LSP Object is defined in Section 7.3 of [RFC8231].  This document
   proposes to define a new LSP-EXTENDED-FLAG TLV for an extended flag
   field in the LSP object.

3.1.  The LSP-EXTENDED-FLAG TLV

   The format of the LSP-EXTENDED-FLAG TLV follows the format of all
   PCEP TLVs as defined in [RFC5440] and is shown in Figure 1.













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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=TBD1           |           Length              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //                 LSP Extended Flags                          //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


              Figure 1: Figure 1: LSP-EXTENDED-FLAG TLV Format


   Type (16 bits): TBD1.

   Length (16 bits): indicates the length of the value portion in bytes.
   It MUST be in multiples of 4 and greater than 0.

   LSP Extended Flags: this contains an array of units of 32-bit flags
   numbered from the most significant as bit zero, where each bit
   represents one LSP flag (for operation, feature, or state).  The LSP
   Extended Flags field SHOULD use the minimal amount of space needed to
   encode the flag bits.  Currently, no bits are assigned.  Unassigned
   bits MUST be set to zero on transmission and MUST be ignored on
   receipt.

   As an example of usage of the LSP-EXTENDED-FLAG TLV, the E-flag is
   requested for entropy label configuration as proposed in
   [I-D.peng-pce-entropy-label-position].

3.2.  Processing

   The LSP Extended Flags field is an array of units of 32 flags, to be
   allocated starting from the most significant bit.  The bits of the
   LSP Extended Flags field will be assigned by future documents.  This
   document does not define any flags.  Flags that an implementation is
   not supporting MUST be set to zero on transmission.  Implementations
   that do not understand any particular flag MUST ignore the flag.

   Note that PCEP peers MUST handle varying lengths of the LSP-EXTENDED-
   FLAG TLV.

   If a PCEP speaker receives the LSP-EXTENDED-FLAG TLV of a length more
   than it currently supports or understands, it MUST ignore the bits
   beyond that length.





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   If a PCEP speaker receives the LSP-EXTENDED-FLAG TLV of a length less
   than the one supported by the implementation, it MUST treat the bits
   beyond the length to be unset.

4.  Advice for Specification of New Flags

   Following the model provided in [RFC8786] Section 3.1, we provide the
   following advice for new specifications that define additional flags.
   Each such specification is expected to describe the interaction
   between these new flags and any existing flags.  In particular, new
   specifications are expected to explain how to handle the cases when
   both new and pre-existing flags are set.  They are also expected to
   discuss any security implications of the additional flags (if any)
   and their interactions with existing flags.

5.  Backward Compatibility

   The LSP-EXTENDED-FLAG TLV defined in this document does not introduce
   any backward compatibility issues.  An implementation that does not
   understand or support the LSP-EXTENDED-FLAG TLV MUST ignore the TLV
   as per [RFC5440].  It is expected that future documents that define
   bits in the LSP-EXTENDED-FLAG TLV will also define the error case
   handling required for missing LSP-EXTENDED-FLAG TLV if it MUST be
   present.

   Further, any additional bits in the LSP-EXTENDED-FLAG TLV that are
   not understood by an implementation MUST be ignored.  It is expected
   that future documents that define bits in the LSP-EXTENDED-FLAG TLV
   will take that into consideration.

6.  IANA Considerations

6.1.  LSP Object

6.1.1.  PCEP TLV Type Indicators

   IANA is requested to allocate the following TLV Type Indicator value
   within the "PCEP TLV Type Indicators" subregistry of the "Path
   Computation Element Protocol (PCEP) Numbers" registry:

              +=======+===================+=================+
              | Value | Description       | Reference       |
              +=======+===================+=================+
              | TBD1  | LSP-EXTENDED-FLAG | [This document] |
              +-------+-------------------+-----------------+

                                  Table 1




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6.1.2.  LSP Extended Flags Field

   IANA is requested to create a new subregistry called "LSP-EXTENDED-
   FLAG TLV Flag Field", within the "Path Computation Element Protocol
   (PCEP) Numbers" registry to manage the LSP Extended Flags field of
   the LSP-EXTENDED-FLAG TLV.  New values are assigned by Standards
   Action [RFC8126].  Each bit should be tracked with the following
   qualities:

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

   *  Capability description

   *  Defining RFC


   No values are currently defined.  Bits 0-31 should initially be
   marked as "Unassigned".  Bits with a higher ordinal than 31 will be
   added to the registry in future documents if necessary.

7.  Implementation Status

   [NOTE TO RFC EDITOR : This whole section and the reference to
   [RFC7942] is to be removed before publication as an RFC]

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in [RFC7942].
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.

   According to [RFC7942], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

   At the time of posting this version of this document, there are no
   known implementations of this TLV.  It is believed that this would be
   implemented alongside the documents that allocate flags in the TLV.



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8.  Management Considerations

   Implementations receiving set LSP Extended Flags that they do not
   recognize MAY log this.  That could be helpful for diagnosing
   backward compatibility issues with future features that utilize those
   flags.

9.  Security Considerations

   [RFC8231] sets out security considerations for PCEP when used for
   communication with a stateful PCE.  This document does not change
   those considerations.  For LSP Object processing, see [RFC8231].

   The flags for the LSP object and their associated security
   considerations are specified in [RFC8231], [RFC8281], [RFC8623], and
   [I-D.ietf-pce-binding-label-sid].

   This document provides for the future addition of flags in the LSP
   Object.  Any future document that specifies new flags must also
   discuss any associated security implications.  No additional security
   issues are raised in this document beyond those that exist in the
   referenced documents.  Note that the [RFC8231] recommends that the
   stateful PCEP extension are authenticated and encrypted using
   Transport Layer Security (TLS) [RFC8253], as per the recommendations
   and best current practices in [RFC7525].  Assuming that
   recommendation is followed, then the flags will be protected by TLS.

10.  Acknowledgements

   The authors would like to thank Loa Andersson, Adrian Farrel, Aijun
   Wang, and Gyan Mishra for their review, suggestions and comments to
   this document.

11.  Contributors

   The following people have substantially contributed to this document:

           Dhruv Dhody
           Huawei Technologies
           EMail: dhruv.ietf@gmail.com

           Greg Mirsky
           Ericsson
           Email: gregimirsky@gmail.com

12.  References

12.1.  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>.

   [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>.

12.2.  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.peng-pce-entropy-label-position]
              Xiong, Q., Peng, S., and F. Qin, "PCEP Extension for SR-
              MPLS Entropy Label Position", Work in Progress, Internet-
              Draft, draft-peng-pce-entropy-label-position-08, 29 August
              2022, <https://www.ietf.org/archive/id/draft-peng-pce-
              entropy-label-position-08.txt>.

   [RFC5088]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "OSPF Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
              January 2008, <https://www.rfc-editor.org/info/rfc5088>.





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   [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "IS-IS Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
              January 2008, <https://www.rfc-editor.org/info/rfc5089>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", BCP 205,
              RFC 7942, DOI 10.17487/RFC7942, July 2016,
              <https://www.rfc-editor.org/info/rfc7942>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

   [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>.

   [RFC8623]  Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful
              Path Computation Element (PCE) Protocol Extensions for
              Usage with Point-to-Multipoint TE Label Switched Paths
              (LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019,
              <https://www.rfc-editor.org/info/rfc8623>.

   [RFC8786]  Farrel, A., "Updated Rules for Processing Stateful PCE
              Request Parameters Flags", RFC 8786, DOI 10.17487/RFC8786,
              May 2020, <https://www.rfc-editor.org/info/rfc8786>.

Appendix A.  WG Discussion

   The WG discussed the idea of a fixed length (with 32 bits) for LSP-
   EXTENDED-FLAG TLV.  Though 32 bits would be sufficient for quite a
   while, the use of variable length with a multiple of 32-bits allows
   for future extensibility where we would never run out of flags and
   there would not be a need to define yet another TLV in the future.
   Further, note that [RFC5088] and [RFC5089] use the same approach for
   the PCE-CAP-FLAGS Sub-TLV and are found to be useful.




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Author's Address

   Quan Xiong
   ZTE Corporation
   No.6 Huashi Park Rd
   Wuhan
   Hubei, 430223
   China
   Email: xiong.quan@zte.com.cn










































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