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rfc:rfc9005



Internet Engineering Task Force (IETF) S. Litkowski Request for Comments: 9005 Cisco Systems, Inc. Category: Standards Track S. Sivabalan ISSN: 2070-1721 Ciena

                                                           J. Tantsura
                                                      Juniper Networks
                                                           J. Hardwick
                                                   Metaswitch Networks
                                                          李呈 (C. Li)
                                华为技术有限公司 (Huawei Technologies)
                                                            March 2021
Path Computation Element Communication Protocol (PCEP) Extension for
        Associating Policies and Label Switched Paths (LSPs)

Abstract

 This document introduces a simple mechanism to associate policies
 with a group of Label Switched Paths (LSPs) via an extension to the
 Path Computation Element Communication Protocol (PCEP).  The
 extension allows a PCEP speaker to advertise to a PCEP peer that a
 particular LSP belongs to a particular Policy Association Group
 (PAG).

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 https://www.rfc-editor.org/info/rfc9005.

Copyright Notice

 Copyright (c) 2021 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.

Table of Contents

 1.  Introduction
   1.1.  Requirements Language
 2.  Terminology
 3.  Motivation
   3.1.  Policy-Based Constraints
 4.  Overview
 5.  Policy Association Group
   5.1.  POLICY-PARAMETERS-TLV
 6.  Security Considerations
 7.  IANA Considerations
   7.1.  ASSOCIATION Object Type Indicators
   7.2.  PCEP TLV Type Indicators
   7.3.  PCEP Errors
 8.  Manageability Considerations
   8.1.  Control of Function and Policy
   8.2.  Information and Data Models
   8.3.  Liveness Detection and Monitoring
   8.4.  Verifying Correct Operations
   8.5.  Requirements on Other Protocols
   8.6.  Impact on Network Operations
 9.  References
   9.1.  Normative References
   9.2.  Informative References
 Appendix A.  Example of Policy Parameters
 Acknowledgments
 Contributors
 Authors' Addresses

1. Introduction

 [RFC5440] describes the Path Computation Element Communication
 Protocol (PCEP), which enables the communication between a Path
 Computation Client (PCC) and a Path Control Element (PCE) or between
 two PCEs based on the PCE architecture [RFC4655].  [RFC5394] provides
 additional details on policy within the PCE architecture and also
 provides context for the support of PCE policy.
 "Path Computation Element Communication Protocol (PCEP) Extensions
 for Stateful PCE" ([RFC8231]) describes a set of extensions to PCEP
 to enable active control of Multiprotocol Label Switching Traffic
 Engineering (MPLS-TE) and Generalized MPLS (GMPLS) tunnels.
 [RFC8281] describes the setup and teardown of PCE-initiated LSPs
 under the active stateful PCE model without the need for local
 configuration on the PCC, thus allowing for a dynamic network.
 Currently, the LSPs can either be signaled via Resource Reservation
 Protocol Traffic Engineering (RSVP-TE) or segment routed as specified
 in [RFC8664].
 [RFC8697] introduces a generic mechanism to create a grouping of LSPs
 that can then be used to define associations between a set of LSPs
 and a set of attributes (such as configuration parameters or
 behaviors) and is equally applicable to stateful PCE (active and
 passive modes) and stateless PCE.
 This document specifies a PCEP extension to associate one or more
 LSPs with policies using the generic association mechanism.
 A PCEP speaker may want to influence the PCEP peer with respect to
 path selection and other policies.  This document describes a PCEP
 extension to associate policies by creating a Policy Association
 Group (PAG) and encoding this association in PCEP messages.  The
 specification is applicable to both stateful and stateless PCEP
 sessions.
 Note that the actual policy definition and the associated parameters
 are out of scope of this document.

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. Terminology

 The following terminology is used in this document.
 Association parameters:  As described in [RFC8697], the combination
    of the mandatory fields Association Type, Association ID, and
    Association Source in the ASSOCIATION object uniquely identifies
    the association group.  If the optional TLVs -- Global Association
    Source or Extended Association ID -- are included, then they are
    included in combination with mandatory fields to uniquely identify
    the association group.
 Association information:  As described in [RFC8697], the ASSOCIATION
    object could include other optional TLVs based on the Association
    Types that provide "information" related to the association.
 LSR:  Label Switching Router
 MPLS:  Multiprotocol Label Switching
 PAG:  Policy Association Group
 PAT:  Policy Association Type
 PCC:  Path Computation Client; any client application requesting a
    path computation to be performed by a Path Computation Element.
 PCE:  Path Computation Element; an entity (component, application, or
    network node) that is capable of computing a network path or route
    based on a network graph and applying computational constraints.
 PCEP:  Path Computation Element Communication Protocol

3. Motivation

 Paths computed using PCE can be subjected to various policies at both
 the PCE and the PCC.  For example, in a centralized TE scenario,
 network operators may instantiate LSPs and specify policies for
 traffic accounting, path monitoring, telemetry, etc., for some LSPs
 via the stateful PCE.  Similarly, a PCC could request a user-specific
 or service-specific policy to be applied at the PCE, such as a
 constraints relaxation policy, to meet optimal QoS and resiliency
 levels.
 PCEP speakers can use the generic mechanism of [RFC8697] to associate
 a set of LSPs with a policy, without the need to know the details of
 such a policy.  This simplifies network operations, avoids frequent
 software upgrades, and provides the ability to introduce new policies
 more quickly.
                                                          PAG Y
                                           {Service-Specific Policy
                                                     for constraint
             Monitor LSP                                relaxation}
                  |                                          |
                  | PAG X                    PCReq/PCRpt     |
                  V {Monitor LSP}            {PAG Y}         V
               +-----+                   ----------------> +-----+
    _ _ _ _ _ _| PCE |                  |                  | PCE |
   |           +-----+                  |      ----------> +-----+
   | PCInitiate/PCUpd                   |     |    PCReq/PCRpt
   |{PAG X}                             |     |    {PAG Y}
   |                                    |     |
   |              .-----.               |     |         .-----.
   |             (       )              |  +----+      (       )
   |         .--(         )--.          |  |PCC1|--.--(         )--.
   V        (                 )         |  +----+ (                 )
 +---+     (                   )        |        (                   )
 |PCC|----(   (G)MPLS network    )   +----+     ( (G)MPLS network   )
 +---+     (                   )     |PCC2|------(                   )
 PAG X      (                 )      +----+       (                 )
 {Monitor    '--(         )--'                     '--(         )--'
 LSP}            (       )                             (       )
                  '-----'                               '-----'
 Case 1: Policy requested by PCE        Case 2: Policy requested by
         and enforced by PCC                    PCC and enforced by
                                                PCE
       Figure 1: Sample Use Cases for Carrying Policies over PCEP

3.1. Policy-Based Constraints

 In the context of a policy-enabled path computation framework
 [RFC5394], path computation policies may be applied at a PCC, a PCE,
 or both.  A Label Switching Router (LSR) with a policy-enabled PCC
 can receive:
  • A service request via signaling, including over a Network-Network

Interface (NNI) or User-Network Interface (UNI) reference point.

  • A configuration request over a management interface to establish a

service.

 The PCC may apply user-specific or service-specific policies to
 decide how the path selection process should be constrained -- that
 is, which constraints, diversities, optimization criteria, and
 constraint-relaxation strategies should be applied to increase the
 likelihood that the service LSP(s) will be successfully established
 and will provide the necessary QoS and resilience against network
 failures.  The user-specific or service-specific policies are applied
 to the PCC and are then passed to the PCE along with the path
 computation request in the form of constraints [RFC5394].
 The PCEP speaker can use the generic mechanism as per [RFC8697] to
 associate a set of LSPs with user-specific or service-specific
 policies.  This would simplify the path computation message exchanges
 in PCEP.

4. Overview

 As per [RFC8697], LSPs are associated with other LSPs with which they
 interact by adding them to a common association group.  Grouping can
 also be used to define the association between LSPs and the policies
 associated with them.  As described in [RFC8697], the association
 group is uniquely identified by the combination of the following
 fields in the ASSOCIATION object: Association Type, Association ID,
 Association Source, and (if present) Global Association Source or
 Extended Association ID.  This document defines a new Association
 Type called "Policy Association" with value 3 based on the generic
 ASSOCIATION object.  This new Association Type is called "Policy
 Association Type" (PAT).
 [RFC8697] specifies the mechanism for the capability advertisement of
 the Association Types supported by a PCEP speaker by defining an
 ASSOC-Type-List TLV to be carried within an OPEN object.  This
 capability exchange for the PAT MUST be done before using the Policy
 Association.  Thus, the PCEP speaker MUST include the PAT in the
 ASSOC-Type-List TLV and MUST receive the same from the PCEP peer
 before using the PAG in PCEP messages.
 The Policy Association Type (3) is operator configured (as specified
 in [RFC8697]), i.e., the association is created by the operator
 manually on the PCEP peers, and an LSP belonging to this association
 is conveyed via PCEP messages to the PCEP peer.  There is no need to
 convey an explicit Operator-configured Association Range, which could
 only serve to artificially limit the available Association IDs.
 Thus, for the Policy Association Type, the Operator-configured
 Association Range MUST NOT be set and MUST be ignored if received.
 A PAG can have one or more LSPs.  The association parameters
 including Association Identifier, Policy Association Type (PAT), as
 well as the Association Source IP address are manually configured by
 the operator and are used to identify the PAG as described in
 [RFC8697].  The Global Association Source and Extended Association ID
 MAY also be included.
 As per the processing rules specified in Section 6.4 of [RFC8697], if
 a PCEP speaker does not support this Policy Association Type, it
 would return a PCEP error (PCErr) message with Error-Type 26
 "Association Error" and Error-value 1 "Association type is not
 supported".  The PAG and the policy MUST be configured on the PCEP
 peers as per the operator-configured association procedures.  All
 further processing is as per Section 6.4 of [RFC8697].  If a PCE
 speaker receives a PAG in a PCEP message and the Policy Association
 information is not configured, it MUST return a PCErr message with
 Error-Type 26 "Association Error" and Error-value 4 "Association
 unknown".
 Associating a particular LSP with multiple policy groups is allowed
 from a protocol perspective; however, there is no assurance that the
 PCEP speaker will be able to apply multiple policies.  If a PCEP
 speaker does not support handling of multiple policies for an LSP, it
 MUST NOT add the LSP into the association group and MUST return a
 PCErr with Error-Type 26 "Association Error" and Error-value 7
 "Cannot join the association group".

5. Policy Association Group

 Association groups and their memberships are defined using the
 ASSOCIATION object defined in [RFC8697].  Two object types for IPv4
 and IPv6 are defined.  The ASSOCIATION object includes "Association
 type" indicating the type of the association group.  This document
 adds a new Association Type, Policy Association Type (PAT).
 PAG may carry optional TLVs including but not limited to:
 POLICY-PARAMETERS-TLV:
    Used to communicate opaque information useful to applying the
    policy, described in Section 5.1.
 VENDOR-INFORMATION-TLV:
    Used to communicate arbitrary vendor-specific behavioral
    information, described in [RFC7470].

5.1. POLICY-PARAMETERS-TLV

 The ASSOCIATION object (for PAT) can carry an optional POLICY-
 PARAMETERS-TLV with opaque information that is needed to apply the
 policy at the PCEP peer.  In some cases, to apply a PCE policy
 successfully, it is required to also associate some policy parameters
 that need to be evaluated.  This TLV is used to carry those policy
 parameters.  The TLV could include one or more policy-related
 parameters.  The encoding format and the order MUST be known to the
 PCEP peers; this could be done during the configuration of the policy
 (and its association parameters) for the PAG.  The TLV format is as
 per the format of the PCEP TLVs, as defined in [RFC5440] and shown in
 Figure 2.  Only one POLICY-PARAMETERS-TLV can be carried, and only
 the first occurrence is processed.  Any others MUST be ignored.
     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=48               |          Length               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    //                     Policy Parameters                       //
    |                                                               |
    +---------------------------------------------------------------+
               Figure 2: The POLICY-PARAMETERS-TLV Format
 The POLICY-PARAMETERS-TLV type is 48, and it has a variable length.
 The Value field is variable and padded to a 4-byte alignment; padding
 is not included in the Length field.  The PCEP peer implementation
 needs to be aware of the encoding format, order, and meaning of the
 policy parameters well in advance based on the policy.  Note that
 from the protocol point of view, this data is opaque and can be used
 to carry parameters in any format understood by the PCEP peers and
 associated with the policy.  The exact use of this TLV is beyond the
 scope of this document.  Examples are included for illustration
 purposes in Appendix A.
 If the PCEP peer is unaware of the policy parameters associated with
 the policy and it receives the POLICY-PARAMETERS-TLV, it MUST reject
 the PCEP message and send a PCErr message with Error-Type 26
 "Association Error" and Error-value 12 "Not expecting policy
 parameters".  Further, if at least one parameter in the POLICY-
 PARAMETERS-TLV received by the PCEP speaker is considered
 unacceptable in the context of the associated policy (e.g., out of
 range value, badly encoded value, etc.), the PCEP speaker MUST reject
 the PCEP message and send a PCErr message with Error-Type 26
 "Association Error" and Error-value 13 "Unacceptable policy
 parameters".
 Note that the vendor-specific behavioral information is encoded in
 the VENDOR-INFORMATION-TLV, which can be used along with this TLV.

6. Security Considerations

 The security considerations described in [RFC8697], [RFC8231],
 [RFC5394], and [RFC5440] apply to the extensions described in this
 document as well.  In particular, a malicious PCEP speaker could be
 spoofed and used as an attack vector by creating spurious Policy
 Associations as described in [RFC8697].  Further, as described in
 [RFC8697], a spurious LSP can have policies that are inconsistent
 with those of the legitimate LSPs of the group and, thus, cause
 problems in the handling of the policy for the legitimate LSPs.  It
 should be noted that Policy Association could provide an adversary
 with the opportunity to eavesdrop on the relationship between the
 LSPs.  [RFC8697] suggests that the implementations and operators use
 indirect values as a way to hide any sensitive business
 relationships.  Thus, securing the PCEP session using Transport Layer
 Security (TLS) [RFC8253], as per the recommendations and best current
 practices in BCP 195 [RFC7525], is RECOMMENDED.
 Further, extra care needs to be taken by the implementation with
 respect to the POLICY-PARAMETERS-TLV while decoding, verifying, and
 applying these policy variables.  This TLV parsing could be exploited
 by an attacker; thus, extra care must be taken while configuring a
 Policy Association that uses the POLICY-PARAMETERS-TLV and making
 sure that the data is easy to parse and verify before use.  Ensuring
 agreement among all relevant PCEP peers as to the format and layout
 of the policy parameters information is key for correct operations.
 Note that the parser for POLICY-PARAMETERS-TLV is particularly
 sensitive since it is opaque to PCEP and can be used to convey data
 with many different internal structures/formats.  The choice of
 decoder is dependent on the additional metadata associated with the
 policy; thus, additional risk of using a wrong decoder and getting
 garbage results is incurred.  Using standard and well-known policy
 formats could help alleviate those risks.

7. IANA Considerations

7.1. ASSOCIATION Object Type Indicators

 This document defines a new Association Type in the subregistry
 "ASSOCIATION Type Field" of the "Path Computation Element Protocol
 (PCEP) Numbers" registry that was originally defined in [RFC8697].
              +=======+====================+===========+
              | Value | Name               | Reference |
              +=======+====================+===========+
              | 3     | Policy Association | RFC 9005  |
              +-------+--------------------+-----------+
                               Table 1

7.2. PCEP TLV Type Indicators

 The following TLV Type Indicator value has been registered within the
 "PCEP TLV Type Indicators" subregistry of the "Path Computation
 Element Protocol (PCEP) Numbers" registry.
             +=======+=======================+===========+
             | Value | Description           | Reference |
             +=======+=======================+===========+
             | 48    | POLICY-PARAMETERS-TLV | RFC 9005  |
             +-------+-----------------------+-----------+
                                Table 2

7.3. PCEP Errors

 This document defines new Error-values for Error-Type 26 "Association
 Error" defined in [RFC8697].  IANA has allocated new error values
 within the "PCEP-ERROR Object Error Types and Values" subregistry of
 the "Path Computation Element Protocol (PCEP) Numbers" registry as
 follows:
  +============+===================+===================+===========+
  | Error-Type | Meaning           | Error-value       | Reference |
  +============+===================+===================+===========+
  | 26         | Association Error |                   | [RFC8697] |
  +------------+-------------------+-------------------+-----------+
  |            |                   | 12: Not expecting | RFC 9005  |
  |            |                   | policy parameters |           |
  +------------+-------------------+-------------------+-----------+
  |            |                   | 13: Unacceptable  | RFC 9005  |
  |            |                   | policy parameters |           |
  +------------+-------------------+-------------------+-----------+
                               Table 3

8. Manageability Considerations

8.1. Control of Function and Policy

 An operator MUST be allowed to configure the Policy Associations at
 PCEP peers and associate them with the LSPs.  They MAY also allow
 configuration to related policy parameters and provide information on
 the encoding format and order to parse the associated POLICY-
 PARAMETERS-TLV.

8.2. Information and Data Models

 [RFC7420] describes the PCEP MIB; there are no new MIB objects for
 this document.
 The PCEP YANG module is defined in [PCE-PCEP-YANG].  That module
 supports associations as defined in [RFC8697]; thus, it supports the
 Policy Association Groups.
 An implementation SHOULD allow the operator to view the PAG
 configured.  Further implementation SHOULD allow one to view
 associations reported by each peer and the current set of LSPs in the
 PAG.

8.3. Liveness Detection and Monitoring

 The mechanisms defined in this document do not imply any new liveness
 detection and monitoring requirements in addition to those already
 listed in [RFC5440] and [RFC8231].

8.4. Verifying Correct Operations

 Verifying the correct operation of a policy can be performed by
 monitoring various parameters as described in [RFC5440] and
 [RFC8231].  A PCEP implementation SHOULD provide information on
 failed path computation due to applying policy and log error events,
 e.g., parsing failure for a POLICY-PARAMETERS-TLV.

8.5. Requirements on Other Protocols

 The mechanisms defined in this document do not imply any new
 requirements on other protocols.

8.6. Impact on Network Operations

 The mechanisms defined in this document do not have any impact on
 network operations in addition to those already listed in [RFC5440],
 [RFC8231], and [RFC8281].

9. References

9.1. 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>.
 [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>.
 [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>.
 [RFC8697]  Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
            Dhody, D., and Y. Tanaka, "Path Computation Element
            Communication Protocol (PCEP) Extensions for Establishing
            Relationships between Sets of Label Switched Paths
            (LSPs)", RFC 8697, DOI 10.17487/RFC8697, January 2020,
            <https://www.rfc-editor.org/info/rfc8697>.

9.2. Informative References

 [PCE-PCEP-YANG]
            Dhody, D., Ed., Hardwick, J., Beeram, V., and J. Tantsura,
            "A YANG Data Model for Path Computation Element
            Communications Protocol (PCEP)", Work in Progress,
            Internet-Draft, draft-ietf-pce-pcep-yang-16, 22 February
            2021,
            <https://tools.ietf.org/html/draft-ietf-pce-pcep-yang-16>.
 [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>.
 [RFC5394]  Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
            "Policy-Enabled Path Computation Framework", RFC 5394,
            DOI 10.17487/RFC5394, December 2008,
            <https://www.rfc-editor.org/info/rfc5394>.
 [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
            "Network Time Protocol Version 4: Protocol and Algorithms
            Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
            <https://www.rfc-editor.org/info/rfc5905>.
 [RFC7420]  Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
            Hardwick, "Path Computation Element Communication Protocol
            (PCEP) Management Information Base (MIB) Module",
            RFC 7420, DOI 10.17487/RFC7420, December 2014,
            <https://www.rfc-editor.org/info/rfc7420>.
 [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>.
 [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>.
 [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>.
 [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>.

Appendix A. Example of Policy Parameters

 An example could be a monitoring and telemetry policy, P1, that is
 dependent on a profile (GOLD/SILVER/BRONZE) as set by the operator.
 The PCEP peers need to be aware of policy P1 (and its associated
 characteristics) in advance as well the fact that the policy
 parameter will encode the profile of a type string in the POLICY-
 PARAMETERS-TLV.  As an example, LSP1 could encode the PAG with the
 POLICY-PARAMETERS-TLV using the string "GOLD".
 The following is another example where the path computation at the
 PCE could be dependent on when the LSP was configured at the PCC.
 For such a policy, P2, the timestamp can be encoded in the POLICY-
 PARAMETERS-TLV, and the exact encoding could be the 64-bit timestamp
 format as defined in [RFC5905].
 While the above example has a single field in the POLICY-PARAMETERS-
 TLV, it is possible to include multiple fields, but the exact order,
 encoding format, and meanings need to be known in advance at the PCEP
 peers.

Acknowledgments

 We would like to acknowledge and thank Santiago Alvarez, Zafar Ali,
 Luis Tomotaki, Victor Lopez, Rob Shakir, and Clarence Filsfils for
 working on earlier draft versions with similar motivation.
 Special thanks to the authors of [RFC8697].  This document borrowed
 some of its text.  The authors would like to thank Aijun Wang, Peng
 Shuping, and Gyan Mishra for their useful comments.
 Thanks to Hariharan Ananthakrishnan for shepherding this document.
 Thanks to Deborah Brungard for providing comments and being the
 responsible AD for this document.
 Thanks to Nic Leymann for the RTGDIR review.
 Thanks to Benjamin Kaduk and Murray Kucherawy for their comments
 during the IESG review.

Contributors

 The following individuals have contributed extensively:
 Mahendra Singh Negi
 RtBrick Inc
 N-17L, 18th Cross Rd, HSR Layout
 Bangalore 560102
 Karnataka
 India
 Email: mahend.ietf@gmail.com
 Dhruv Dhody
 Huawei Technologies
 Divyashree Techno Park, Whitefield
 Bangalore 560066
 Karnataka
 India
 Email: dhruv.ietf@gmail.com
 The following individuals have contributed text that was
 incorporated:
 Qin Wu
 Huawei Technologies
 101 Software Avenue, Yuhua District
 Nanjing
 Jiangsu, 210012
 China
 Email: sunseawq@huawei.com
 Xian Zhang
 Huawei Technologies
 Bantian, Longgang District
 Shenzhen
 518129
 China
 Email: zhang.xian@huawei.com
 Udayasree Palle
 Email: udayasreereddy@gmail.com
 Mike Koldychev
 Cisco Systems, Inc.
 Canada
 Email: mkoldych@cisco.com

Authors' Addresses

 Stephane Litkowski
 Cisco Systems, Inc.
 11 Rue Camille Desmoulins
 92130 Issy-les-Moulineaux
 France
 Email: slitkows@cisco.com
 Siva Sivabalan
 Ciena
 385 Terry Fox Drive
 Kanata Ontario K2K 0L1
 Canada
 Email: msiva282@gmail.com
 Jeff Tantsura
 Juniper Networks
 Email: jefftant.ietf@gmail.com
 Jonathan Hardwick
 Metaswitch Networks
 33 Genotin Road
 Enfield
 United Kingdom
 Email: Jonathan.Hardwick@metaswitch.com
 Cheng Li
 Huawei Technologies
 Huawei Campus, No. 156 Beiqing Rd.
 Beijing
 100095
 China
 Email: c.l@huawei.com
 Additional contact information:
    李呈
    中国
    100095
    北京
    华为北研所
    华为技术有限公司
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