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Versions: (draft-dhody-pce-association-policy) 00 01 02 03

PCE Working Group                                          D. Dhody, Ed.
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                            S. Sivabalan
Expires: December 21, 2018                           Cisco Systems, Inc.
                                                            S. Litkowski
                                                                  Orange
                                                             J. Tantsura
                                                              Individual
                                                             J. Hardwick
                                                     Metaswitch Networks
                                                           June 19, 2018


     Path Computation Element communication Protocol extension for
                     associating Policies and LSPs
                  draft-ietf-pce-association-policy-03

Abstract

   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
   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 December 21, 2018.

Copyright Notice

   Copyright (c) 2018 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



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   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.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Association object Type Indicators  . . . . . . . . . . .   9
     7.2.  PCEP TLV Type Indicators  . . . . . . . . . . . . . . . .   9
   8.  Manageability Considerations  . . . . . . . . . . . . . . . .   9
     8.1.  Control of Function and Policy  . . . . . . . . . . . . .   9
     8.2.  Information and Data Models . . . . . . . . . . . . . . .   9
     8.3.  Liveness Detection and Monitoring . . . . . . . . . . . .   9
     8.4.  Verify Correct Operations . . . . . . . . . . . . . . . .  10
     8.5.  Requirements On Other Protocols . . . . . . . . . . . . .  10
     8.6.  Impact On Network Operations  . . . . . . . . . . . . . .  10
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Appendix A.  Contributor Addresses  . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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.

   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 setup and teardown of PCE-initiated



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   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 can be segment routed as
   specified in [I-D.ietf-pce-segment-routing].

   [I-D.ietf-pce-association-group] 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 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 Policy Association Group
   (PAG) and encoding this association in PCEP messages.  The
   specification is applicable to both stateful and stateless PCEP
   sessions.

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
      [I-D.ietf-pce-association-group], 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 identifying the association
      group.

   Association information:  As described in
      [I-D.ietf-pce-association-group], the ASSOCIATION object could
      include other optional TLVs based on the association types, that
      provides 'information' related to the association.




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   LSR:  Label Switch Router.

   LSR:  Label Switch Router.

   MPLS:  Multiprotocol Label Switching.

   PAG:  Policy Association Group.

   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 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
   [I-D.ietf-pce-association-group] 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 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           |
                    V {Monitor LSP}         {PAG Y}            V
                 +-----+                   ----------------> +-----+
      _ _ _ _ _ _| PCE |                  |                  | PCE |
     |           +-----+                  |      ----------> +-----+
     | PCEInitiate                        |     |    PCReq
     |{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 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 signaling, 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
   [I-D.ietf-pce-association-group] 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 [I-D.ietf-pce-association-group], 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") for Policy
      Association Group (PAG)

   [I-D.ietf-pce-association-group] 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.  Policy Association Type) MUST be
   done before using the policy association.  Thus the PCEP speaker MUST
   include the Policy Association Type (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.  The LSP
   belonging to this associations is conveyed via PCEP messages to the
   PCEP peer.  Operator-configured Association Range SHOULD 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, 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 [I-D.ietf-pce-association-group].  The Global
   Association Source and Extended Association ID MAY also be included.

   As per the processing rules specified in section 5.4 of
   [I-D.ietf-pce-association-group], if a PCEP speaker does not support
   this Policy association-type, it would return a PCErr message with
   Error-Type 26 (Early allocation by IANA) "Association Error" and
   Error-Value 1 "Association-type is not supported".  Since the PAG is



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   opaque in nature, the PAG and the policy MUST be configured on the
   PCEP peers as per the operator-configured association procedures.
   All processing is as per section 5.4 of
   [I-D.ietf-pce-association-group].  If a PCE speaker receives PAG in a
   PCEP message, and the policy association information is not
   configured, it MUST return a PCErr message with Error-Type TBD
   "Association Error" and Error- Value 4 "Association unknown".  If
   some of the association information [I-D.ietf-pce-association-group]
   (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 (Early
   allocation by IANA) "Association Error" and Error-Value 5 "Operator-
   configured association information mismatch".

5.  Policy Association Group

   Association groups and their memberships are defined using the
   ASSOCIATION object defined in [I-D.ietf-pce-association-group].  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 behavioral information, described in [RFC7470].

5.1.  Policy Parameters TLV

   The POLICY-PARAMETERS-TLV is an optional TLV that can be carried in
   ASSOCIATION object (with "Policy Association Type") 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 configuration of 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 behavioral information is encoded in
   VENDOR-INFORMATION-TLV which can be used along with this TLV.

6.  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 [I-D.ietf-pce-association-group] in itself.

   Some deployments may find policy associations and their implications
   as extra sensitive and thus should employ suitable PCEP security
   mechanisms like [RFC8253].  Also extra care needs to be taken by the
   implementation with respect to POLICY-PARAMETERS-TLV while decoding,
   verifying and applying these policy variables.




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7.  IANA Considerations

7.1.  Association object Type Indicators

   This document defines the following new association type originally
   defined in [I-D.ietf-pce-association-group].

   Value     Name                        Reference

   TBD1      Policy Association Type     [This I.D.]

7.2.  PCEP TLV Type Indicators

   The following TLV Type Indicator values are requested within the
   "PCEP TLV Type Indicators" subregistry of the "Path Computation
   Element Protocol (PCEP) Numbers" registry:

   Value     Description                 Reference

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

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 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.

8.2.  Information and Data Models

   An implementation SHOULD allow the operator to view the PAG
   configured.  Further implementation SHOULD allow to view the current
   set of LSPs in the PAG.  To serve this purpose, the PCEP YANG module
   [I-D.ietf-pce-pcep-yang] includes association groups and can be used
   for PAG.

8.3.  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].







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8.4.  Verify Correct Operations

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

8.5.  Requirements On Other Protocols

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

8.6.  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].

9.  Acknowledgments

   A special thanks to author of [I-D.ietf-pce-association-group], this
   document borrow some of the text from it.

10.  References

10.1.  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>.







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   [I-D.ietf-pce-association-group]
              Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
              Dhody, D., and Y. Tanaka, "PCEP Extensions for
              Establishing Relationships Between Sets of LSPs", draft-
              ietf-pce-association-group-06 (work in progress), June
              2018.

10.2.  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,
              <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>.

   [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>.

   [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>.

   [I-D.ietf-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "PCEP Extensions for Segment Routing",
              draft-ietf-pce-segment-routing-11 (work in progress),
              November 2017.

   [I-D.ietf-pce-pcep-yang]
              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-07 (work in progress), March 2018.




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Appendix A.  Contributor Addresses

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

   EMail: sunseawq@huawei.com

   Clarence Filsfils
   Cisco Systems, Inc.
   Pegasus Parc
   De kleetlaan 6a, DIEGEM  BRABANT 1831
   BELGIUM

   Email: cfilsfil@cisco.com

   Xian Zhang
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   P.R.China

   EMail: zhang.xian@huawei.com

   Udayasree Palle
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: udayasreereddy@gmail.com


Authors' Addresses

   Dhruv Dhody (editor)
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: dhruv.ietf@gmail.com







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

   EMail: msiva@cisco.com


   Stephane Litkowski
   Orange

   EMail: stephane.litkowski@orange.com


   Jeff Tantsura
   Individual

   EMail: jefftant.ietf@gmail.com


   Jonathan Hardwick
   Metaswitch Networks
   100 Church Street
   Enfield, Middlesex
   UK

   EMail: Jonathan.Hardwick@metaswitch.com























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