PCE Working Group                                           S. Litkowski
Internet-Draft                                              S. Sivabalan
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: December 23, 2020                                   J. Tantsura
                                                            Apstra, Inc.
                                                             J. Hardwick
                                                     Metaswitch Networks
                                                                 M. Negi
                                                           RtBrick India
                                                                   C. Li
                                                     Huawei Technologies
                                                           June 21, 2020

  Path Computation Element communication Protocol (PCEP) extension for
          associating Policies and Label Switched Paths (LSPs)


   This document introduces a simple mechanism to associate policies to
   a group of Label Switched Paths (LSPs) via an extension to the Path
   Computation Element (PCE) Communication Protocol (PCEP).

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 December 23, 2020.

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

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   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Policy based Constraints  . . . . . . . . . . . . . . . .   5
   4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Policy Association Group  . . . . . . . . . . . . . . . . . .   7
     5.1.  Policy Parameters TLV . . . . . . . . . . . . . . . . . .   7
   6.  Implementation Status . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Cisco's Implementation  . . . . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Association object Type Indicators  . . . . . . . . . . .  10
     8.2.  PCEP TLV Type Indicators  . . . . . . . . . . . . . . . .  10
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  10
     9.1.  Control of Function and Policy  . . . . . . . . . . . . .  10
     9.2.  Information and Data Models . . . . . . . . . . . . . . .  10
     9.3.  Liveness Detection and Monitoring . . . . . . . . . . . .  11
     9.4.  Verify Correct Operations . . . . . . . . . . . . . . . .  11
     9.5.  Requirements on Other Protocols . . . . . . . . . . . . .  11
     9.6.  Impact on Network Operations  . . . . . . . . . . . . . .  11
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Appendix A.  Contributor Addresses  . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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.

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   PCEP Extensions for Stateful PCE Model [RFC8231] describes a set of
   extensions to PCEP to enable active control of Multiprotocol Label
   Switching Traffic Engineering (MPLS-TE) and Generalzied MPLS (GMPLS)
   tunnels.  [RFC8281] describes the set-up 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 signalled via Resource
   Reservation Protocol Traffic Engineering (RSVP-TE) or can be segment
   routed as specified in [RFC8664].

   [RFC8697] introduces a generic mechanism to create a grouping of LSPs
   which can then be used to define associations between a set of LSPs
   and a set of attributes (such as configuration parameters or
   behaviours) 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 Policy Association Group
   (PAG) and encoding this association in PCEP messages.  The
   specification is applicable to both stateful and stateless PCEP

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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 identify 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.

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   Association information:  As described in [RFC8697], the ASSOCIATION
      object could include other optional TLVs based on the association
      types, that provides 'information' related to the association.

   LSR:  Label Switch 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

   PCEP:  Path Computation Element Communication Protocol.

3.  Motivation

   Paths computed using PCE can be subjected to various policies on both
   PCE and PCC.  For example, in a centralized traffic engineering
   scenario, network operators may instantiate LSPs and specifies
   policies for traffic steering, path monitoring, etc., for some LSPs
   via the Stateful PCE.  Similarly, a PCC could request a user- or
   service-specific policy to be applied at the PCE, such as constraints
   relaxation to meet optimal QoS and resiliency.

   PCEP speaker can use the generic mechanism as per [RFC8697] to
   associate a set of LSPs with a policy, without the need to know the
   details of such a policy, which simplifies network operations, avoids
   frequent software upgrades, as well as provides an ability to
   introduce new policy faster.

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                                                            PAG Y
                                             {Service-Specific Policy
                                                       for constraint
           Initiate & Monitor LSP                         relaxation}
                    |                                          |
                    | PAG X                    PCReq/PCRpt     |
                    V {Monitor LSP}            {PAG Y}         V
                 +-----+                   ----------------> +-----+
      _ _ _ _ _ _| PCE |                  |                  | PCE |
     |           +-----+                  |      ----------> +-----+
     | PCInitiate                         |     |    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

    Figure 1: Sample use-cases for carrying policies over PCEP session

3.1.  Policy based Constraints

   In the context of policy-enabled path computation [RFC5394], path
   computation policies may be applied at both a PCC and a PCE.
   Consider an Label Switch Router (LSR) with a policy enabled PCC, it
   receives a service request via signalling, including over a Network-
   Network Interface (NNI) or User Network Interface (UNI) reference
   point, or receives a configuration request over a management
   interface to establish a service.  The PCC may also apply user- or
   service-specific policies to decide how the path selection process
   should be constrained, that is, which constraints, diversities,
   optimization criterion, and constraint relaxation strategies should
   be applied in order for the service LSP(s) to have a likelihood to be
   successfully established and provide necessary QoS and resilience
   against network failures.  The user- or service-specific policies

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   applied to PCC and are then passed to the PCE along with the Path
   computation request, in the form of constraints [RFC5394].

   PCEP speaker can use the generic mechanism as per [RFC8697] to
   associate a set of LSPs with policy and its resulting path
   computation constraints.  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 association between LSPs and policies
   associated to them.  One new Association type is defined in this
   document, based on the generic Association object -

   o  Association type = TBD1 ("Policy Association Type (PAT)" ) for
      Policy Association Group (PAG).

   [RFC8697] specify the mechanism for the capability advertisement of
   the Association types supported by a PCEP speaker by defining a
   ASSOC-Type-List TLV to be carried within an OPEN object.  This
   capability exchange for the association type described in this
   document (i.e.  PAT) MUST be done before using the policy
   association.  Thus the PCEP speaker MUST include the PAT (TBD1) in
   the ASSOC-Type-List TLV before using the PAG in the PCEP messages.

   This Association type is operator-configured association in nature
   and created by the operator manually on the PCEP peers.  An LSP
   belonging to this association is conveyed via PCEP messages to the
   PCEP peer.  Operator-configured Association Range need not be set for
   this association-type, and MUST be ignored, so that the full range of
   association identifier can be utilized.

   A PAG can have one or more LSPs and its associated policy.  The
   association parameters including association identifier, Association
   type (Policy), as well as the association source IP address is
   manually configured by the operator and is 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 PCErr message with Error-Type 26 "Association Error"
   and Error-Value 1 "Association type is not supported".  Since the PAG
   is opaque in nature, 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

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   speaker receives 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".  If some of the association information [RFC8697] (the TLVs
   defined in this document) received from the peer does not match the
   local configured values, the PCEP speaker MUST reject the PCEP
   message and send a PCErr message with Error-Type 26 "Association
   Error" and Error-Value 5 "Operator-configured association information

   Associating a particular LSP to multiple policy groups is authorized
   from a protocol perspective, however there is no assurance that the
   PCE will be able to apply multiple policies.

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
   add a new Association type -

   Association type = TBD1 ("Policy Association type") for PAG.

   PAG may carry optional TLVs including but not limited to -

   o  POLICY-PARAMETERS-TLV: Used to communicate opaque information
      useful to apply the policy, described in Section 5.1.

   o  VENDOR-INFORMATION-TLV: Used to communicate arbitrary vendor
      specific behavioural information, described in [RFC7470].

5.1.  Policy Parameters TLV

   The POLICY-PARAMETERS-TLV is an optional TLV that can be carried in
   ASSOCIATION object (for PAT) to carry opaque information 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 needs to be evaluated, to successfully apply the said
   policy.  This TLV is used to carry those policy parameters.  The TLV
   could include one or more policy related parameter.  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 and any others MUST be ignored.

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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=TBD2             |          Length               |
      |                                                               |
      //                     Policy Parameters                       //
      |                                                               |

                Figure 2: The POLICY-PARAMETERS-TLV format

   The type of the POLICY-PARAMETERS-TLV is TBD2 and it has a variable
   length.  The Value field is variable field padded to a 4-bytes
   alignment; padding is not included in the Length field.  The PCEP
   peer implementation need 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 to the policy.  The exact use of
   this TLV is beyond the scope of this document.

   If the PCEP peer is unaware of the policy parameters associated with
   the policy and it receives the POLICY-PARAMETERS-TLV, it MUST ignore
   the TLV and SHOULD log this event.  Further, if one or more
   parameters received in the POLICY-PARAMETERS-TLV received by the PCEP
   speaker are considered as unacceptable in the context of the
   associated policy (e.g. out of range value, badly encoded value...),
   the PCEP speaker MUST NOT apply the received policy and SHOULD log
   this event.

   Note that, the vendor specific behavioural information is encoded in
   VENDOR-INFORMATION-TLV which can be used along with this TLV.

6.  Implementation Status

   [Note to the RFC Editor - remove this section before publication, as
   well as remove the reference to RFC 7942.]

   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

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   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 catalogue of available implementations or their
   features.  Readers are advised to note that other implementations may

   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".

6.1.  Cisco's Implementation

   o  Organization: Cisco Systems, Inc.

   o  Implementation: IOS-XR PCE and PCC.

   o  Description: The PCEP extension specified in this document is used
      to convey traffic steering policies.

   o  Maturity Level: In shipping product.

   o  Coverage: Partial.

   o  Contact: msiva@cisco.com.

7.  Security Considerations

   This document defines one new type for association, which do not add
   any new security concerns beyond those discussed in [RFC5440],
   [RFC8231] and [RFC8697] in itself.

   Extra care needs to be taken by the implementation with respect to
   POLICY-PARAMETERS-TLV while decoding, verifying and applying these
   policy variables.  This TLV parsing could be exploited by an

   Some deployments may find policy associations and their implications
   as extra sensitive and 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.

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8.  IANA Considerations

8.1.  Association object Type Indicators

   This document defines a new Association type.  The sub-registry
   "ASSOCIATION Type Field" of the "Path Computation Element Protocol
   (PCEP) Numbers" registry was originally defined in [RFC8697].  IANA
   is requested to make the following allocation.

   Value     Name                        Reference

   TBD1      Policy Association          [This.I-D]

8.2.  PCEP TLV Type Indicators

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

   Value     Description                 Reference

   TBD2      POLICY-PARAMETERS-TLV       [This.I-D]

9.  Manageability Considerations

9.1.  Control of Function and Policy

   An operator MUST be allowed to configure the policy associations at
   PCEP peers and associate it with the LSPs.  They MAY also allow
   configuration to related policy parameters, in which case the an
   operator MUST also be allowed to set the encoding format and order to
   parse the associated policy parameters TLV.

9.2.  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 [I-D.ietf-pce-pcep-yang].  This
   module supports associations as defined in [RFC8697] and thus support
   the Policy Association groups.

   An implementation SHOULD allow the operator to view the PAG
   configured.  Further implementation SHOULD allow to view associations
   reported by each peer, and the current set of LSPs in the PAG.

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9.3.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to those already
   listed in [RFC5440], [RFC8231], and [RFC8281].

9.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   [RFC5440], [RFC8231], and [RFC8281].

9.5.  Requirements on Other Protocols

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

9.6.  Impact on Network Operations

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

10.  Acknowledgments

   A special thanks to author of [RFC8697], this document borrow some of
   the text from it.

11.  References

11.1.  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,

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,

   [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>.

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   [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,

   [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,

11.2.  Informative References

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,

   [RFC5394]  Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
              "Policy-Enabled Path Computation Framework", RFC 5394,
              DOI 10.17487/RFC5394, December 2008,

   [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,

   [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,

   [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,

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   [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,

   [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,

   [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,

              Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
              YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", draft-ietf-pce-pcep-
              yang-13 (work in progress), October 2019.

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Appendix A.  Contributor Addresses

   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066

   EMail: dhruv.ietf@gmail.com

   Qin Wu
   Huawei Technologies
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012

   EMail: sunseawq@huawei.com

   Xian Zhang
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129

   EMail: zhang.xian@huawei.com

   Udayasree Palle

   EMail: udayasreereddy@gmail.com

Authors' Addresses

   Stephane Litkowski
   Cisco Systems, Inc.
   11 Rue Camille Desmoulins
   Issy-les-Moulineaux  92130

   EMail: slitkows@cisco.com

Litkowski, et al.       Expires December 23, 2020              [Page 14]

Internet-Draft                ASSOC-POLICY                     June 2020

   Siva Sivabalan
   Cisco Systems, Inc.
   2000 Innovation Drive
   Kanata, Ontario  K2K 3E8

   EMail: msiva@cisco.com

   Jeff Tantsura
   Apstra, Inc.

   EMail: jefftant.ietf@gmail.com

   Jonathan Hardwick
   Metaswitch Networks
   100 Church Street
   Enfield, Middlesex

   EMail: Jonathan.Hardwick@metaswitch.com

   Mahendra Singh Negi
   RtBrick India
   N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3
   Bangalore, Karnataka  560102

   EMail: mahend.ietf@gmail.com

   Cheng Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing  100095

   EMail: chengli13@huawei.com

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