PCE Working Group                                                C. Lin
Internet Draft                                     New H3C Technologies
Intended status: Standards Track
Expires: January 19, 2024                                 July 19, 2025




     Extensions to the Path Computation Element Communication Protocol
                  (PCEP) for SR Policy Performance Metric

               draft-lin-pce-sr-policy-performance-metric-00


Abstract

   This document describes a way to report the performance metrics for
   Traffic Engineering (TE) Policy by the Path Computation Element
   Communication Protocol(PCEP).

Status of this Memo

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   This Internet-Draft will expire on January 19, 2024.

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Table of Contents


   1. Introduction...................................................2
      1.1. Requirements Language.....................................3
   2. Extensions to METRIC Object....................................3
   3. Security Considerations........................................4
   4. IANA Considerations............................................4
   5. References.....................................................5
      5.1. Normative References......................................5
      5.2. Informative References....................................6
   Authors' Addresses................................................6

1. Introduction

   The Path Computation Element (PCE) is a network component,
   application, or node that is capable of computing a network path or
   route based on a network graph and applying computational
   constraints.  The PCE Communication Protocol (PCEP) enables
   communication between a PCE and Path Computation Clients (PCCs),
   facilitating the computation of optimal paths for traffic flows.

   [RFC8664] introduces the concept of Segment Routing Policy (SR
   Policy), which is a set of candidate paths that can be used to steer
   traffic through a network.  Each candidate path is represented by a
   list of segments, and the path can be dynamically adjusted based on
   network conditions and requirements.

   [I-D.ietf-spring-stamp-srpm] describes the procedures for
   Performance Measurement in SR networks, using STAMP as defined in
   [RFC8762]. The described procedure is used for SR paths
   [RFC8402](including SR Policies [RFC9256]).

   The METRIC object is defined in Section 7.8 of [RFC5440]. The METRIC
   object can be carried in the PCReq message as a constraint for the
   metric to be calculated, or it can be included in the PCRep message
   with the calculated path metric value. In some network scenarios,
   the PCE needs to obtain the performance information of TE Policies,
   which can be used for better service placement and more efficient
   utilization of network resources. Currently, there is no definition
   for the real-time test metric values of SR paths. When the real-time
   metric values of SR paths are measured through [I-D.ietf-spring-
   stamp-srpm], they need to be reported to the PCE via the PCRep
   message.

   This document describes a way to report the performance metrics for
   Traffic Engineering (TE) Policy by the Path Computation Element
   Communication Protocol(PCEP).

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   It defines new flag and new metric types for the METRIC object
   required to support Reporting the performance metric of SR Policy.

1.1. 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.

2. Extensions to METRIC Object

   The performance metric of SR Policy may be measured at the headend,
   for example, by using STAMP for SR Policy [I-D.ietf-spring-stamp-
   srpm]. But the measurement methods are out of the scope of this
   document.

   The METRIC object is defined in Section 7.8 of [RFC5440]. This
   document expands the Flag field to indicate that the METRIC object
   contains an actual measurement metric.

   Add the definition of the R bit in the Flags of the METRIC Object
   TLV:

   Codespace of the Flag field (Metric Object)

        Bit      Description              Reference

        TBD     Real Measuring metric    This document

   R (Real Measuring Metric - 1 bit): When set in a PCRep message, this
   indicates that the PCC MUST provide the actual measured path metric
   value in the PCRep message for the corresponding metric.

   For the one-way measurement of SR Policy performance metrics, the
   following directions are used to report:

   * Set R=1 in the Flags field and and Type=12 of the metric object to
      in dicate the measured Delay metric of the path.

   * Set R=1 in the Flags field and Type=13 of the metric object to
      indicate the measured Path Delay Variation metric of the path.

   * Set R=1 in the Flags field and Type=14  of the metric object to
      indicate the measured Loss metric of the path.



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   * Set R=1 in the Flags field and Type=22  of the metric object to
      indicate the measured Path Min Delay Metric of the path.

   Define a new maximum one-way delay type:

   T=TBD1: Path Max Delay. Set R=1 in the Flags field and Type=Path Max
      Delay of the metric object to indicate the measured Path Max
      Delay Metric of the path.



   Five new metric types are defined to report the two-way performance
   metrics of SR Policy, as follows:

   T=TBD2: Round-trip Delay: This metric Type advertises the average
      round-trip delay for SR Path.

   T=TBD3: Round-trip Min Delay: This metric Type advertises the
      minimum round-trip delay for SR Path.

   T=TBD4: Round-trip Max Delay: This metric Type advertises the
      maximum round-trip delay for SR Path.

   T=TBD5: Round-trip Variation: This metric Type advertises the
      average round-trip delay variation for SR Path.

   T=TBD6: Round-trip Loss: This metric Type advertises the the round-
      trip loss for SR Path.

   When reporting the bidirectional delay, minimum delay, maximum
   delay, variation, and loss in a PCRep message, the R bit for the new
   position needs to be set.

3. Security Considerations

   This document does not introduce any new security consideration.

4. IANA Considerations

   Codespace of the Flag field (Metric Object)

        Bit      Description              Reference

        TBD     Real Measuring metric    This document





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   Add the definition of the R bit in the Flags of the METRIC Object
   TLV:

   R (Real Measuring Metric - 1 bit): When set in a PCRep message, this
   indicates that the PCC MUST provide the actual measured path metric
   value in the PCRep message for the corresponding metric.



   Codespace of the T field (Metric Object)

       Value      Meaning               Reference

         TBD      Path Max Delay        This document

         TBD      Round-trip Delay      This document

         TBD      Round-trip Min Delay  This document

         TBD      Round-trip Max Delay  This document

         TBD      Round-trip Variation  This document

         TBD      Round-trip Loss       This document

5. References

5.1. 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>.

   [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>.

   [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>.

   [RFC9552]  Talaulikar, K., Ed., "Distribution of Link-State and

              Traffic Engineering Information Using BGP", RFC 9552,



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                 DOI 10.17487/RFC9552, December 2023, <https://www.rfc-
             editor.org/info/rfc9552>.

5.2. Informative References

   [I-D.ietf-spring-stamp-srpm] Gandhi, R., Filsfils, C., Voyer, D.,
             Chen, M., and R. F.Foote, "Performance Measurement Using
             Simple Two-Way Active Measurement Protocol (STAMP) for
             Segment Routing Networks", Work in Progress, Internet-
             Draft, draft-ietf-spring-stamp-srpm-19, 20 June 2025,
             <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
             stamp-srpm-19>.



Authors' Addresses

   Changwang Lin
   New H3C Technologies
   China
   Email: linchangwang.04414@h3c.com



























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