



PCE Working Group                                               I. Minei
Internet-Draft                                              Google, Inc.
Intended status: Standards Track                               E. Crabbe
Expires: February 2, 2020                         Individual Contributor
                                                            S. Sivabalan
                                                     Cisco Systems, Inc.
                                                      H. Ananthakrishnan
                                                                 Netflix
                                                                D. Dhody
                                                                  Huawei
                                                               Y. Tanaka
                                          NTT Communications Corporation
                                                          August 1, 2019


 Path Computation Element Communication Protocol (PCEP) Extensions for
 Establishing Relationships Between Sets of Label Switched Paths (LSPs)
                  draft-ietf-pce-association-group-10

Abstract

   This document introduces a generic mechanism to create a grouping of
   Label Switched Paths (LSPs) in the context of a Path Computation
   Element (PCE).  This grouping can then be used to define associations
   between sets of LSPs or between a set of LSPs and a set of attributes
   (such as configuration parameters or behaviours), and is equally
   applicable to the stateful PCE (active and passive modes) as well as
   the stateless PCE.

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.

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/.





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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   This Internet-Draft will expire on February 2, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Architectural Overview  . . . . . . . . . . . . . . . . . . .   4
     3.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Relationship with the SVEC List . . . . . . . . . . . . .   5
     3.3.  Operation Overview  . . . . . . . . . . . . . . . . . . .   5
     3.4.  Operator-configured Association Range . . . . . . . . . .   6
   4.  Discovery of Supported Association Types  . . . . . . . . . .   7
     4.1.  ASSOC-Type-List TLV . . . . . . . . . . . . . . . . . . .   7
       4.1.1.  Procedure . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Operator-configured Association Range TLV . . . . . . . . . .   8
     5.1.  Procedure . . . . . . . . . . . . . . . . . . . . . . . .  10
   6.  ASSOCIATION Object  . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Object Definition . . . . . . . . . . . . . . . . . . . .  11
       6.1.1.  Global Association Source TLV . . . . . . . . . . . .  13
       6.1.2.  Extended Association ID TLV . . . . . . . . . . . . .  13
       6.1.3.  Association Source  . . . . . . . . . . . . . . . . .  14
       6.1.4.  Unique Identification for an Association Group  . . .  14
     6.2.  Relationship with the RSVP ASSOCIATION  . . . . . . . . .  15
     6.3.  Object Encoding in PCEP messages  . . . . . . . . . . . .  15
       6.3.1.  Stateful PCEP messages  . . . . . . . . . . . . . . .  15
       6.3.2.  Request Message . . . . . . . . . . . . . . . . . . .  17
       6.3.3.  Reply Message . . . . . . . . . . . . . . . . . . . .  18
     6.4.  Processing Rules  . . . . . . . . . . . . . . . . . . . .  19



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   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
     7.1.  PCEP Object . . . . . . . . . . . . . . . . . . . . . . .  21
     7.2.  PCEP TLV  . . . . . . . . . . . . . . . . . . . . . . . .  22
     7.3.  Association Flags . . . . . . . . . . . . . . . . . . . .  22
     7.4.  Association Type  . . . . . . . . . . . . . . . . . . . .  23
     7.5.  PCEP-Error Object . . . . . . . . . . . . . . . . . . . .  23
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   9.  Manageability Considerations  . . . . . . . . . . . . . . . .  24
     9.1.  Control of Function and Policy  . . . . . . . . . . . . .  24
     9.2.  Information and Data Models . . . . . . . . . . . . . . .  24
     9.3.  Liveness Detection and Monitoring . . . . . . . . . . . .  25
     9.4.  Verify Correct Operations . . . . . . . . . . . . . . . .  25
     9.5.  Requirements on Other Protocols . . . . . . . . . . . . .  25
     9.6.  Impact on Network Operations  . . . . . . . . . . . . . .  25
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  25
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  25
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  26
     12.2.  Informative References . . . . . . . . . . . . . . . . .  27
   Appendix A.  Example for Operator-configured Association Range  .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  29

1.  Introduction

   [RFC5440] describes the Path Computation Element (PCE) Communication
   Protocol (PCEP).  PCEP enables the communication between a Path
   Computation Client (PCC) and a PCE, or between PCE and PCE, for the
   purpose of computation of Multiprotocol Label Switching (MPLS) as
   well as Generalized MPLS (GMPLS) Traffic Engineering Label Switched
   Path (TE LSP) characteristics.

   [RFC8231] specifies a set of extensions to PCEP to enable stateful
   control of TE LSPs within and across PCEP sessions in compliance with
   [RFC4657].  It includes mechanisms to effect LSP State
   Synchronization between PCCs and PCEs, delegation of control over
   LSPs to PCEs, and PCE control of timing and sequence of path
   computations within and across PCEP sessions.  The model of operation
   where LSPs are initiated from the PCE is described in [RFC8281].

   [RFC4872] defines the RSVP ASSOCIATION object, which was defined in
   the context of GMPLS-controlled Label Switched Paths (LSPs) to be
   used to associate recovery LSPs with the LSP they are protecting.
   This object also has broader applicability as a mechanism to
   associate RSVP state and [RFC6780] described how the ASSOCIATION
   object can be more generally applied by defining the Extended
   ASSOCIATION Object.





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   This document introduces a generic mechanism to create a grouping of
   LSPs.  This grouping can then be used to define associations between
   sets of LSPs or 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.  The
   associations could be created dynamically and conveyed to a PCEP peer
   within PCEP, or it could be configured manually by an operator on the
   PCEP peers.  Refer Section 3.3 for more details.

2.  Terminology

   This document uses the following terms defined in [RFC5440]: PCC,
   PCE, PCEP Peer, Path Computation Request (PCReq), Path Computation
   Reply (PCRep), and PCEP Error (PCErr).

   This document uses the following terms defined in [RFC8051]: Stateful
   PCE, Active Stateful PCE, Passive Stateful PCE, and Delegation.

   This document uses the following terms defined in [RFC8231]: LSP
   State Report (PCRpt), LSP Update Request (PCUpd), and State Timeout
   Interval.

   This document uses the following terms defined in [RFC8281]: PCE-
   initiated LSP, and LSP Initiate Request (PCInitiate).

3.  Architectural Overview

3.1.  Motivation

   Stateful PCE provides the ability to update existing LSPs and to
   instantiate new ones.  There are various situations where several
   LSPs need to share common information.  E.g., to support for PCE-
   controlled make-before-break, an association between the original and
   the re-optimized path is desired.  Similarly, for end-to-end
   protection, the association between working and protection LSPs is
   required (see [I-D.ietf-pce-stateful-path-protection]).  For diverse
   paths, an association between a group of LSPs could be used (see
   [I-D.ietf-pce-association-diversity]).  Another use for the LSP
   grouping is for applying a common set of configuration parameters or
   behaviours to a set of LSPs.

   For a stateless PCE, it might be useful to associate a path
   computation request to an association group, thus enabling it to
   associate a common set of policy, configuration parameters or
   behaviours with the request.

   Some associations could be created dynamically, such as association
   between the working and protection LSPs of a tunnel, whereas some



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   associations could be created by the operator manually, such as
   policy-based association, where the LSP could join an operator-
   configured existing association.

   Rather than creating separate mechanisms for each use case, this
   document defines a generic mechanism that can be reused as needed.

3.2.  Relationship with the SVEC List

   Note that, [RFC5440] defines a mechanism for the synchronization of a
   set of path computation requests by using the SVEC (Synchronization
   VECtor) object, that specifies the list of synchronized requests that
   can either be dependent or independent.  The SVEC object identifies
   the relationship between the set of path computation requests,
   identified by 'Request-ID-number' in RP (Request Parameters) object.
   [RFC6007] further clarifies the use of the SVEC list for synchronized
   path computations when computing dependent requests as well as
   describes a number of usage scenarios for SVEC lists within single-
   domain and multi-domain environments.

   The motivation behind the association group defined in this document
   and the SVEC object are quite different, though some use cases may
   overlap.  PCEP extensions that define a new association type should
   clarify the relationship between the SVEC object and the association
   type, if any.

3.3.  Operation Overview

   LSPs are associated with other LSPs with which they interact by
   adding them to a common association group.  Association groups as
   defined in this document can be applied to LSPs originating at the
   same head end or different head ends.

   Some associations could be created dynamically by a PCEP speaker and
   the associations (along with the set of LSPs) are conveyed to a PCEP
   peer.  Whereas some associations are configured by the operator on
   the PCEP peers involved beforehand, a PCEP speaker then could ask for
   a LSP to join the operator-configured association.  Usage of dynamic
   and configured association is usually dependent on the type of the
   association.

   For the operator-configured association, the association parameters
   such as the association identifier, association type, as well as the
   association source IP address, are manually configured by the
   operator.  In case of dynamic association, the association parameters
   such as the association identifier, are allocated dynamically by the
   PCEP speaker, the association source is set as local PCEP speaker




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   address, unless local policy dictates otherwise, in which case
   association source is set based on the local policy.

   The dynamically created association can be reported to the PCEP peer
   via the PCEP messages as per the stateful extensions.  When the
   operator-configured association is known to the PCEP peer beforehand,
   a PCEP peer could ask for a LSP to join the operator-configured
   association via the stateful PCEP messages.

   The associations are properties of the LSP and thus could be stored
   in the LSP state database.  The dynamic association exists as long as
   the LSP state exists.  In case of PCEP session termination, the LSP
   state clean-up MUST also take care of associations.

   Multiple types of associations can exist, each with their own
   association identifier space.  The definition of the different
   association types and their behaviours is outside the scope of this
   document.  The establishment and removal of the association
   relationship can be done on a per LSP basis.  An LSP may join
   multiple association groups, of different or of the same association
   type.

3.4.  Operator-configured Association Range

   Some association types are dynamic, some are operator-configured and
   some could be both.  For the association types that could be both
   dynamic and operator-configured and use the same association source,
   it is necessary to distinguish a range of association identifiers
   that are marked for operator-configured associations to avoid any
   association identifier clash within the scope of the association
   source.  This document assumes that these two ranges are configured.

   A range of association identifiers for each Association type (and
   Association Source) are kept for the operator-configured
   associations.  Dynamic associations MUST NOT use the association
   identifier from this range.

   This range as set at the PCEP speaker (PCC or PCE, as an association
   source) needs to be communicated to a PCEP peer in the Open Message.
   A new TLV is defined in this specification for this purpose
   (Section 5).  See Appendix A for an example.

   Association identifier range for sources other than the PCEP speaker
   (for example an NMS system) is not communicated in PCEP and the
   procedure for operator-configured association range setting is
   outside the scope of this document.





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4.  Discovery of Supported Association Types

   This section defines PCEP extensions so as to support the capability
   advertisement of the association types supported by a PCEP speaker.

   A new PCEP ASSOC-Type-List (Association Types list) TLV is defined.
   The PCEP ASSOC-Type-List TLV is carried within an OPEN object.  This
   way, during PCEP session-setup phase, a PCEP speaker can advertise to
   a PCEP peer the list of supported Association types.

4.1.  ASSOC-Type-List TLV

   The PCEP ASSOC-Type-List TLV is OPTIONAL.  It MAY be carried within
   an OPEN object sent by a PCEP speaker in an Open message to a PCEP
   peer so as to indicate the list of supported Association types.

   The PCEP ASSOC-Type-List TLV format is compliant with the PCEP TLV
   format defined in [RFC5440].  That is, the TLV is composed of 2
   octets for the type, 2 octets specifying the TLV length, and a Value
   field.  The Length field defines the length of the value portion in
   octets.  The TLV is padded to 4-octet alignment, and padding is not
   included in the Length field (e.g., a 3-octet value would have a
   length of three, but the total size of the TLV would be eight
   octets).

   The PCEP ASSOC-Type-List TLV has the following format:

   TYPE:    TBD
   LENGTH:  N * 2 (where N is the number of association types)
   VALUE:   list of 2-byte association type code points, identifying
            the association types supported by the sender of the Open
            message.

      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                  |            Length             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Assoc-type #1        |      Assoc-type #2            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     //                                                             //
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Assoc-type #N        |       padding                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                 Figure 1: The ASSOC-Type-List TLV format




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   Assoc-type (2 bytes): Association type code point identifier.  IANA
   manages the "ASSOCIATION Type Field" code point registry (see
   Section 7.4).

4.1.1.  Procedure

   An ASSOC-Type-List TLV within an OPEN object in an Open message is
   included by a PCEP speaker in order to advertise a set of one or more
   supported association types.  The ASSOC-Type-List TLV MUST NOT appear
   more than once in an OPEN object.  If it appears more than once, the
   PCEP session MUST be rejected with error type 1 and error value 1
   (PCEP session establishment failure / Reception of an invalid Open
   message).  As specified in [RFC5440], a PCEP peer that does not
   recognize the ASSOC-Type-List TLV will silently ignore it.

   Association type (to be defined in other documents) can specify if
   the association type advertisement is mandatory for it.  Thus, the
   ASSOC-Type-List TLV MUST be included if at least one mandatory
   association type needs to be advertised and the ASSOC-Type-List TLV
   MAY be included otherwise.  For an association type that specifies
   that the advertisement is mandatory, a missing Assoc-type in the
   ASSOC-Type-List TLV (or missing ASSOC-Type-List TLV) is to be
   interpreted as the association type is not supported by the PCEP
   speaker.

   The absence of the ASSOC-Type-List TLV in an OPEN object MUST be
   interpreted as an absence of information on the list of supported
   Association types (rather than the Association type is not
   supported).  In this case, the PCEP speaker could still use the
   ASSOCIATION object: if the peer does not support the association, it
   will react as per the procedure described in Section 6.4.

   In case the use of the ASSOC-Type-List TLV is triggered by support
   for a mandatory association type, then it is RECOMMENDED that the
   PCEP implementation include all supported Association types
   (including optional) to ease the operations of the PCEP peer.

5.  Operator-configured Association Range TLV

   This section defines PCEP extension to support the advertisement of
   the Operator-configured Association Range used for an Association
   type by the PCEP speaker (as an Association source).

   A new PCEP OP-CONF-ASSOC-RANGE (Operator-configured Association
   Range) TLV is defined.  The PCEP OP-CONF-ASSOC-RANGE TLV is carried
   within an OPEN object.  This way, during PCEP session-setup phase, a
   PCEP speaker can advertise to a PCEP peer the Operator-configured
   Association Range for an association type.



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   The PCEP OP-CONF-ASSOC-RANGE TLV is OPTIONAL.  It MAY be carried
   within an OPEN object sent by a PCEP speaker in an Open message to a
   PCEP peer.  The OP-CONF-ASSOC-RANGE TLV format is compliant with the
   PCEP TLV format defined in [RFC5440].  That is, the TLV is composed
   of 2 bytes for the type, 2 bytes specifying the TLV length, and a
   Value field.  The Length field defines the length of the value
   portion in bytes.

   The PCEP OP-CONF-ASSOC-RANGE TLV has the following format:

   TYPE:    29 (Early allocation by IANA)
   LENGTH:  N * 8 (where N is the number of association types)
   VALUE:

    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                  |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Reserved          |          Assoc-type #1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Start-Assoc-ID #1        |           Range #1            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                                                             //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Reserved          |          Assoc-type #N        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Start-Assoc-ID #N        |           Range #N            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



               Figure 2: The OP-CONF-ASSOC-RANGE TLV format

   The Value portion includes the following fields, repeated for each
   association type:

      Reserved (2 bytes): This field MUST be set to 0 on transmission
      and MUST be ignored on receipt.

      Assoc-type (2 bytes): The association type (Section 7.4).  The
      association types are defined in separate documents.

      Start-Assoc-ID (2 bytes): The start association identifier for the
      Operator-configured Association Range for the particular
      association type.  The values 0 and 0xffff MUST NOT be used and on
      receipt of these values in the TLV, the session is rejected with
      error message sent (see Section 5.1).



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      Range (2 bytes): The number of associations marked for the
      Operator-configured Associations.  The Range MUST be greater than
      0, and it MUST be such that (Start-Assoc-ID + Range) do not cross
      the association identifier range of 0xffff.  In case this
      condition is not satisfied, the session is rejected with error
      message sent (see Section 5.1).

5.1.  Procedure

   A PCEP speaker MAY include an OP-CONF-ASSOC-RANGE TLV within an OPEN
   object in an Open message sent to a PCEP peer in order to advertise
   the Operator-configured Association Range for an association type.
   The OP-CONF-ASSOC-RANGE TLV MUST NOT appear more than once in an OPEN
   object.  If it appears more than once, the PCEP session MUST be
   rejected with error type 1 and error value 1 (PCEP session
   establishment failure / Reception of an invalid Open message).

   As specified in [RFC5440], a PCEP peer that does not recognize the
   OP-CONF-ASSOC-RANGE TLV will silently ignore it.

   The Operator-configured Association Range SHOULD be included for each
   association type that could be both dynamic and operator-configured.
   For association types that are only dynamic or only operator-
   configured, this TLV MAY be skipped, in which case the full range of
   association identifier is considered dynamic or operator-configured
   respectively.  Each association type (that are defined in separate
   documents) can specify the default value for the operator-configured
   association range for their respective association type.

   The absence of the OP-CONF-ASSOC-RANGE TLV in an OPEN object MUST be
   interpreted as an absence of explicit Operator-configured Association
   Range at the PCEP peer.  In this case, the default behavior as per
   each association type applies.  If the association source is not a
   PCEP speaker, the default value for the operator-configured
   association range is used for the association source.

   If the Assoc-type is not recognized or supported by the PCEP speaker,
   it MUST ignore that respective Start-Assoc-ID and Range.  If the
   Assoc-type is recognized/supported but the Start-Assoc-ID or Range
   are set incorrectly, the PCEP session MUST be rejected with error
   type 1 and error value 1 (PCEP session establishment failure /
   Reception of an invalid Open message).  The incorrect range include
   the case when the (Start-Assoc-ID + Range) crosses the association
   identifier range of 0xffff.

   A given Assoc-type MAY appear more than once in the OP-CONF-ASSOC-
   RANGE TLV in the case of a non-contiguous Operator-configured
   Association Range.  The PCEP speaker originating this TLV MUST NOT



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   carry overlapping ranges for an association type.  If a PCEP peer
   receives overlapping ranges for an association type, it MUST consider
   the Open message malformed and MUST reject the PCEP session with
   error type 1 and error value 1 (PCEP session establishment failure /
   Reception of an invalid Open message).

   There may be cases where an operator-configured association was
   configured with association parameters (such as association
   identifier, association type and association source) at the local
   PCEP speaker, and later the PCEP session gets established with the
   association source and a new operator-configured range is learned
   during session establishment.  At this time, the local PCEP speaker
   MUST remove any associations that are not in the new operator-
   configured range (by disassociating any LSPs that are part of it (and
   notifying this change to the PCEP peer)).  If a PCEP speaker receives
   an association for an operator-configured association and the
   association identifier is not in the operator-configured association
   range for the association type and association source, it MUST
   generate an error (as described in Section 6.4).

6.  ASSOCIATION Object

6.1.  Object Definition

   Association groups and their memberships are defined using a new
   ASSOCIATION object.

   ASSOCIATION Object-Class is 40 (Early allocation by IANA).

   ASSOCIATION Object-Type is 1 for IPv4 and its format is shown in
   Figure 3:


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |            Flags            |R|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Association type         |      Association ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              IPv4 Association Source                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                   Optional TLVs                             //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 3: The IPv4 ASSOCIATION Object format




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   ASSOCIATION Object-Type is 2 for IPv6 and its format is shown in
   Figure 4:


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |            Flags            |R|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Association type         |      Association ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                    IPv6 Association Source                    |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                   Optional TLVs                             //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 4: The IPv6 ASSOCIATION Object format

   Reserved (2-byte): MUST be set to 0 and ignored upon receipt.

   Flags (2-byte): The following flags are currently defined:

   R (Removal - 1 bit):  when set, the requesting PCEP peer requires the
      removal of an LSP from the association group.  When unset, the
      PCEP peer indicates that the LSP is added or retained as part of
      the association group.  This flag is used for the ASSOCIATION
      object in the PCRpt and the PCUpd message, the flag is ignored in
      other PCEP messages.

   The unassigned flags MUST be set to zero on transmission and MUST be
   ignored on receipt.

   Association type (2-byte): the association type (Section 7.4).  The
   association types are defined in separate documents.

   Association ID (2-byte): the identifier of the association group.
   When combined with other association parameters, such as Association
   Type and Association Source, this value uniquely identifies an
   association group.  The values 0xffff and 0x0 are reserved.  The
   value 0xffff is used to indicate all association groups and could be
   used with R flag to indicate removal for all associations for the LSP
   within the scope of association type and association source.





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   Association Source: Contains a valid IPv4 address (4 bytes) if the
   ASSOCIATION Object-Type is 1 or a valid IPv6 address (16 bytes) if
   the ASSOCIATION Object-Type is 2.  The address provides scoping for
   the Association ID.  See Section 6.1.3 for details.

   Optional TLVs: The optional TLVs follow the PCEP TLV format of
   [RFC5440].  This document defines two optional TLVs.  Other documents
   can define more TLVs in future.

6.1.1.  Global Association Source TLV

   The Global Association Source TLV is an optional TLV for use in the
   Association Object.  The meaning and the usage of Global Association
   Source is as per Section 4 of [RFC6780].


    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                  |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Global Association Source                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



            Figure 5: The Global Association Source TLV format

   Type: 30 (Early allocation by IANA).

   Length: Fixed value of 4 bytes.

   Global Association Source: as defined in Section 4 of [RFC6780].

6.1.2.  Extended Association ID TLV

   The Extended Association ID TLV is an optional TLV for use in the
   Association Object.  The meaning and the usage of Extended
   Association ID is as per Section 4 of [RFC6780].












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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                  |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                Extended Association ID                      //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



             Figure 6: The Extended Association ID TLV format

   Type: 31 (Early allocation by IANA).

   Length: variable.

   Extended Association ID: as defined in Section 4 of [RFC6780].

6.1.3.  Association Source

   The Association Source field in the ASSOCIATION object is set to a
   valid IP address to identify the node that originates the
   association.  In case of dynamic associations, the association source
   is usually set as the local PCEP speaker address, unless local policy
   dictates otherwise, in which case association source is set based on
   the local policy.  In case of PCE redundancy, local policy could set
   the source as a virtual IP address which identifies all instances of
   the PCE.  In case of operator-configured association, the association
   source is manually configured and it could be set as one of the PCEP
   speakers, Network Management System (NMS), or any other valid IP
   address that scopes the association identifier for the association
   type.

6.1.4.  Unique Identification for an 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 MUST be
   included in combination with mandatory fields to uniquely identify
   the association group.  In this document, all these fields are
   collectively called 'association parameters'.  Note that the
   ASSOCIATION object MAY include other optional TLVs (not defined in
   this document) based on the association types, that provides
   'information' related to the association type, this document uses the
   term 'association information' for it.





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6.2.  Relationship with the RSVP ASSOCIATION

   The format of PCEP ASSOCIATION Object defined in this document is
   aligned with the RSVP ASSOCIATION object ([RFC6780]).  Various
   Association types related to RSVP association are defined in
   [RFC4872], [RFC4873], and [RFC7551].  The PCEP extensions that define
   new association types, should clarify how the PCEP associations would
   work with RSVP associations and vice-versa.

6.3.  Object Encoding in PCEP messages

   Message formats in this document are expressed using Reduced BNF
   (RBNF) as used in [RFC5440] and defined in [RFC5511].

6.3.1.  Stateful PCEP messages

   The ASSOCIATION Object MAY be carried in the Path Computation Update
   (PCUpd), Path Computation Report (PCRpt) and Path Computation
   Initiate (PCInitiate) messages.

   When carried in PCRpt message, it is used to report the association
   group membership pertaining to a LSP to a stateful PCE.  The PCRpt
   message are used for both initial state synchronization operations
   (Section 5.6 of [RFC8231]) as well as whenever the state of the LSP
   changes.  If the LSP belongs to an association group, then the
   associations MUST be included during the state synchronization
   operations.

   The PCRpt message can also be used to remove an LSP from one or more
   association groups by setting the R flag to 1 in the ASSOCIATION
   object.

   When an LSP is first reported to the PCE, the PCRpt message MUST
   include all the association groups that it belongs to.  Any
   subsequent report message SHOULD include only the associations that
   are being modified or removed.

   The PCRpt message is defined in [RFC8231] and updated as below:













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      <PCRpt Message> ::= <Common Header>
                          <state-report-list>
      Where:

         <state-report-list> ::= <state-report>[<state-report-list>]

         <state-report> ::= [<SRP>]
                            <LSP>
                            [<association-list>]
                            <path>
       Where:
         <path>::= <intended-path>
                   [<actual-attribute-list><actual-path>]
                   <intended-attribute-list>


         <association-list> ::= <ASSOCIATION> [<association-list>]

   When an LSP is delegated to a stateful PCE, the stateful PCE can
   create a new association group for this LSP, or associate it with one
   or more existing association groups.  This is done by including the
   ASSOCIATION Object in a PCUpd message.  A stateful PCE can also
   remove a delegated LSP from one or more association groups by setting
   the R flag to 1 in the ASSOCIATION object.

   The PCUpd message SHOULD include the association groups that are
   being modified or removed, there is no need to include associations
   that remains unchanged.

   The PCUpd message is defined in [RFC8231] and updated as below:

       <PCUpd Message> ::= <Common Header>
                           <update-request-list>
    Where:

       <update-request-list> ::= <update-request>[<update-request-list>]

       <update-request> ::= <SRP>
                            <LSP>
                            [<association-list>]
                            <path>
    Where:
       <path>::= <intended-path><intended-attribute-list>

       <association-list> ::= <ASSOCIATION> [<association-list>]






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   Unless a PCEP speaker wants to delete an association from an LSP or
   make changes to the association, it does not need to carry the
   ASSOCIATION object in future stateful messages.

   A PCE initiating a new LSP can also include the association groups
   that this LSP belongs to.  This is done by including the ASSOCIATION
   Object in a PCInitiate message.  The PCInitiate message MUST include
   all the association groups that it belongs to.  The PCInitiate
   message is defined in [RFC8281] and updated as below:

   <PCInitiate Message> ::= <Common Header>
                            <PCE-initiated-lsp-list>
   Where:

   <PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
                                [<PCE-initiated-lsp-list>]

   <PCE-initiated-lsp-request> ::= (<PCE-initiated-lsp-instantiation>|
                                   <PCE-initiated-lsp-deletion>)

   <PCE-initiated-lsp-instantiation> ::= <SRP>
                                         <LSP>
                                         [<END-POINTS>]
                                         <ERO>
                                         [<association-list>]
                                         [<attribute-list>]

   Where:
   <association-list> ::= <ASSOCIATION> [<association-list>]

6.3.2.  Request Message

   In case of passive (stateful or stateless) PCE, the ASSOCIATION
   Object is OPTIONAL and MAY be carried in the Path Computation Request
   (PCReq) message.

   When carried in a PCReq message, the ASSOCIATION Object is used to
   associate the path computation request to an association group.  The
   association (and the other LSPs) should be known to the PCE
   beforehand.  These could be operator-configured or dynamically
   learned before via stateful PCEP messages.  The R flag in ASSOCIATION
   object within PCReq message MUST be set to 0 while sending and
   ignored on receipt.

   The PCReq message is defined in [RFC5440] and updated in [RFC8231] ,
   it is further updated below for association:





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   <PCReq Message>::= <Common Header>
                      [<svec-list>]
                      <request-list>

   Where:
         <svec-list>::= <SVEC>[<svec-list>]
         <request-list>::= <request>[<request-list>]

         <request>::= <RP>
                      <END-POINTS>
                      [<LSP>]
                      [<LSPA>]
                      [<BANDWIDTH>]
                      [<metric-list>]
                      [<association-list>]
                      [<RRO>[<BANDWIDTH>]]
                      [<IRO>]
                      [<LOAD-BALANCING>]

   Where:
         <association-list> ::= <ASSOCIATION> [<association-list>]

   Note that the LSP object MAY be present for the passive stateful PCE
   mode.

6.3.3.  Reply Message

   In case of passive (stateful or stateless) PCE, the ASSOCIATION
   Object is OPTIONAL and MAY be carried in the Path Computation Reply
   (PCRep) message with the NO-PATH object.  The ASSOCIATION object in
   PCRep message indicates the association group that cause the PCE to
   fail to find a path.

   The PCRep message is defined in [RFC5440] and updated in [RFC8231] ,
   it is further updated below for association:
















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   <PCRep Message> ::= <Common Header>
                       <response-list>
   Where:

   <response-list>::=<response>[<response-list>]

   <response>::=<RP>
                [<LSP>]
                [<NO-PATH>]
                [<association-list>]
                [<attribute-list>]
                [<path-list>]

   Where:
         <association-list> ::= <ASSOCIATION> [<association-list>]

   Note that the LSP object MAY be present for the passive stateful PCE
   mode.

6.4.  Processing Rules

   Association groups can be operator-configured on the necessary PCEP
   speakers and the PCEP speakers can join the existing association
   groups.  In addition, a PCC or a PCE can create association groups
   dynamically and the PCEP speaker can also report the associations to
   its peer via PCEP messages.  The operator-configured associations are
   created via configurations (where all association parameters are
   manually set) and exist until explicitly removed via configurations.
   The PCEP speaker can add LSPs to these configured associations and
   carry this via stateful PCEP messages.  The dynamic associations are
   created dynamically by the PCEP speaker (where all association
   parameters are populated dynamically).  The association group is
   attached to the LSP state, and the association group exists till
   there is at least one LSP as part of the association.  As described
   in Section 6.1.4, the association parameters are the combination of
   Association type, Association ID and Association Source as well as
   optional global source and extended association identifier, that
   uniquely identifies an association group.  The information related to
   the association types encoded via the TLVs of a particular
   association type (not described in this document) are the association
   information (Section 6.1.4).

   If a PCEP speaker does not recognize the ASSOCIATION object in the
   stateful message, it will return a PCErr message with Error-Type
   "Unknown Object" as described in [RFC5440].  In case of PCReq
   message, the PCE would react based on the P flag as per [RFC5440].
   If a PCEP speaker understands the ASSOCIATION object but does not
   support the Association type, it MUST return a PCErr message with



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   Error-Type 26 (Early allocation by IANA) "Association Error" and
   Error-Value 1 "Association type is not supported".  If any
   association parameters are invalid in the ASSOCIATION object, the
   PCEP speaker would consider this as malformed object and handle it as
   malformed message [RFC5440].  On receiving a PCEP message with
   ASSOCIATION, if a PCEP speaker finds that too many LSPs belong to the
   association group, it MUST return a PCErr message with Error-Type 26
   (Early allocation by IANA) "Association Error" and Error-Value 2 "Too
   many LSPs in the association group".  If a PCEP speaker cannot handle
   a new association, it MUST return a PCErr message with Error-Type 26
   (Early allocation by IANA) "Association Error" and Error-Value 3 "Too
   many association groups".  These numbers MAY be set by operator or
   decided based on a local policy.

   If a PCE peer is unwilling or unable to process the ASSOCIATION
   object in the stateful message, it MUST return a PCErr message with
   the Error-Type "Not supported object" and follow the relevant
   procedures described in [RFC5440].  In case of PCReq message, the PCE
   would react based on the P flag as per [RFC5440].  On receiving a
   PCEP message with ASSOCIATION, if a PCEP speaker could not add the
   LSP to the association group for any reason, it MUST return a PCErr
   message with Error-Type 26 (Early allocation by IANA) "Association
   Error" and Error-Value 7 "Cannot join the association group".

   If a PCEP speaker receives an ASSOCIATION object for an operator-
   configured association and the association identifier is not in the
   operator-configured association range for the Association type and
   Association Source, it MUST return a PCErr message with Error-Type 26
   (Early allocation by IANA) "Association Error" and Error-Value 8
   "Association identifier not in range".

   If a PCEP speaker receives ASSOCIATION in PCReq message, and the
   association is not known (association is not configured, or created
   dynamically, or learned from a PCEP peer), it MUST return a PCErr
   message with Error-Type 26 (Early allocation by IANA) "Association
   Error" and Error-Value 4 "Association unknown".

   If the association information (related to the association group as a
   whole) received from the peer does not match with the local operator-
   configured information, it MUST return a PCErr message with Error-
   Type 26 (Early allocation by IANA) "Association Error" and Error-
   Value 5 "Operator-configured association information mismatch".  On
   receiving association information (related to the association group
   as a whole) that does not match with the association information
   previously received about the same association from a peer, it MUST
   return a PCErr message with Error-Type 26 (Early allocation by IANA)
   "Association Error" and Error-Value 6 "Association information
   mismatch".  Note that information related to each LSP within the



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   association as part of the association information TLVs could be
   different.

   If a PCEP speaker receives an ASSOCIATION object with the R bit set
   for removal, and the association group (identified by association
   parameters) is not known, it MUST return a PCErr message with Error-
   Type 26 (Early allocation by IANA) "Association Error" and Error-
   Value 4 "Association unknown".

   The dynamic associations are cleared along with the LSP state
   information as per the [RFC8231].  When a PCEP session is terminated,
   after expiry of State Timeout Interval at PCC, the LSP state
   associated with that PCEP session is reverted to operator-defined
   default parameters or behaviours.  Same procedure is also followed
   for the association groups.  On session termination at the PCE, when
   the LSP state reported by PCC is cleared, the association groups are
   also cleared.  When there are no LSPs in an association group, the
   association is considered to be empty and thus deleted.

   In case the LSP is delegated to another PCE on session failure, the
   associations (and association information) set by the PCE remains
   intact, unless updated by the new PCE that takes over.

   Upon LSP delegation revocation, the PCC MAY clear the association
   created by the PCE, but in order to avoid traffic loss, it SHOULD
   perform this in a make-before-break fashion (same as [RFC8231]).

7.  IANA Considerations

   IANA maintains the "Path Computation Element Protocol (PCEP) Numbers"
   registry at <http://www.iana.org/assignments/pcep>.

7.1.  PCEP Object

   The "PCEP Numbers" registry contains a subregistry "PCEP Objects".
   IANA is requested to confirm the early allocation of the following
   code point in the PCEP Objects registry.

      Object-Class Value   Name                               Reference

   40 (Early allocation by Association                        [This.I-D]
            IANA)
                           Object-Type
                           0: Reserved
                           1: IPv4
                           2: IPv6





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7.2.  PCEP TLV

   IANA is requested to confirm the early allocation of the following
   code point in the "PCEP TLV Type Indicators" registry.

               Value     Meaning                     Reference
             29 (Early   Operator-configured         [This.I-D]
           allocation by Association Range
               IANA)
             30 (Early   Global Association Source   [This.I-D]
           allocation by
               IANA)
             31 (Early   Extended Association ID     [This.I-D]
           allocation by
               IANA)

   IANA is requested to fix the meaning for value 31 in the above
   registry to 'Extended Association ID', it is currently mentioned as
   'Extended Association Id'.

   IANA is also requested to make a new assignment for the existing
   "PCEP TLV Type Indicators" registry as follows:

               Value     Meaning                     Reference
                TBD      ASSOC-Type-List             [This.I-D]

7.3.  Association Flags

   This document requests IANA to create a subregistry of the "PCEP
   Numbers" for the bits carried in the Flags field of the ASSOCIATION
   object.  The subregistry is called "ASSOCIATION Flags Field".  New
   values are assigned by Standards Action [RFC8126].  Each bit should
   be tracked with the following qualities:

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

   o  Capability description

   o  Defining RFC

           Bit    Description                        Reference

           15     R (Removal)                        [This.I-D]








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7.4.  Association Type

   This document requests IANA to create a subregistry of the "PCEP
   Numbers" for the Association Type field of the the ASSOCIATION
   object.  The subregistry is called "ASSOCIATION Type Field".  New
   values are to be assigned by Standards Action [RFC8126].  Each value
   should be tracked with the following qualities:

   o  Type

   o  Name

   o  Reference

   There are no association types specified in this document, future
   documents should request the assignment of association types from
   this subregistry.

7.5.  PCEP-Error Object

   IANA is requested to confirm the early allocation of the following
   code points within the "PCEP-ERROR Object Error Types and Values"
   sub-registry of the "PCEP Numbers" registry, as follows:


       Error-Type  Meaning
          26       Association Error [This.I-D]
       (early      Error-value=0:
       alloc by       Unassigned
       IANA)       Error-value=1:
                      Association type is not supported
                   Error-value=2:
                     Too many LSPs in the association group
                   Error-value=3:
                     Too many association groups
                   Error-value=4:
                     Association unknown
                   Error-value=5:
                     Operator-configured association
                     information mismatch
                   Error-value=6:
                     Association information mismatch
                   Error-value=7:
                     Cannot join the association group
                   Error-value=8:
                     Association identifier not in range





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8.  Security Considerations

   The security considerations described in [RFC8231] and [RFC5440]
   apply to the extensions described in this document as well.
   Additional considerations related to a malicious PCEP speaker are
   introduced, as associations could be spoofed and could be used as an
   attack vector.  An attacker could attempt to create too many
   associations in an attempt to load the PCEP peer.  The PCEP peer
   responds with PCErr as described in Section 6.4.  An attacker could
   impact LSP operations by creating bogus associations.  Further,
   association groups could provides an adversary with the opportunity
   to eavesdrop on the relationship between the LSPs.  Thus securing the
   PCEP session using Transport Layer Security (TLS) [RFC8253], as per
   the recommendations and best current practices in [RFC7525], is
   RECOMMENDED.

   Much of the information carried in the ASSOCIATION object, as per
   this document is not extra sensitive.  It often reflects information
   that can also be derived from the LSP Database, but association
   provides a much easier grouping of related LSPs and messages.
   Implementations and operator can and should use indirect values in
   ASSOCIATION as a way to hide any sensitive business relationships.

9.  Manageability Considerations

   All manageability requirements and considerations listed in [RFC5440]
   and [RFC8231] apply to PCEP protocol extensions defined in this
   document.  In addition, requirements and considerations listed in
   this section apply.

9.1.  Control of Function and Policy

   A PCE or PCC implementation MUST allow operator-configured
   associations and SHOULD allow setting of the operator-configured
   association range (Section 3.4) as described in this document.

9.2.  Information and Data Models

   The PCEP YANG module is defined in [I-D.ietf-pce-pcep-yang].  In
   future, this YANG module should be extended or augmented to provide
   the following additional information relating to association groups.

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





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   It might also be useful to find out how many associations for each
   association type currently exist and to know how many free
   association identifiers are available for a particular association
   type and source.

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].

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] and [RFC8231].

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 [RFC5440] and [RFC8231] also apply to PCEP
   extensions defined in this document.

10.  Acknowledgments

   We would like to thank Yuji Kamite and Joshua George for their
   contributions to this document.  Also thanks to Venugopal Reddy,
   Cyril Margaria, Rakesh Gandhi, Mike Koldychev, and Adrian Farrel for
   their useful comments.

   We would like to thank Julien Meuric for shepherding this document
   and providing comments with text suggestions.

   Thanks to Stig Venaas for the RTGDIR review comments.

   Thanks to Alvaro Retana, Mirja Kuhlewind, Martin Vigoureux, Barry
   Leiba, Eric Vyncke, Suresh Krishnan, and Benjamin Kaduk for the IESG
   comments.

11.  Contributors







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   Stephane Litkowski
   Orange

   Email: stephane.litkowski@orange.com

   Xian Zhang
   Huawei Technologies
   F3-1-B RnD Center, Huawei Base
   Bantian, Longgang District
   Shenzhen 518129
   China

   Email: zhang.xian@huawei.com

   Mustapha Aissaoui
   Nokia

   Email: mustapha.aissaoui@nokia.com



12.  References

12.1.  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>.

   [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
              Used to Form Encoding Rules in Various Routing Protocol
              Specifications", RFC 5511, DOI 10.17487/RFC5511, April
              2009, <https://www.rfc-editor.org/info/rfc5511>.

   [RFC6780]  Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
              ASSOCIATION Object Extensions", RFC 6780,
              DOI 10.17487/RFC6780, October 2012,
              <https://www.rfc-editor.org/info/rfc6780>.







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   [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>.

   [RFC8051]  Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
              Stateful Path Computation Element (PCE)", RFC 8051,
              DOI 10.17487/RFC8051, January 2017,
              <https://www.rfc-editor.org/info/rfc8051>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [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>.

12.2.  Informative References

   [RFC4657]  Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol Generic
              Requirements", RFC 4657, DOI 10.17487/RFC4657, September
              2006, <https://www.rfc-editor.org/info/rfc4657>.

   [RFC4872]  Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
              Ed., "RSVP-TE Extensions in Support of End-to-End
              Generalized Multi-Protocol Label Switching (GMPLS)
              Recovery", RFC 4872, DOI 10.17487/RFC4872, May 2007,
              <https://www.rfc-editor.org/info/rfc4872>.

   [RFC4873]  Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
              "GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC4873,
              May 2007, <https://www.rfc-editor.org/info/rfc4873>.



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   [RFC6007]  Nishioka, I. and D. King, "Use of the Synchronization
              VECtor (SVEC) List for Synchronized Dependent Path
              Computations", RFC 6007, DOI 10.17487/RFC6007, September
              2010, <https://www.rfc-editor.org/info/rfc6007>.

   [RFC7551]  Zhang, F., Ed., Jing, R., and R. Gandhi, Ed., "RSVP-TE
              Extensions for Associated Bidirectional Label Switched
              Paths (LSPs)", RFC 7551, DOI 10.17487/RFC7551, May 2015,
              <https://www.rfc-editor.org/info/rfc7551>.

   [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>.

   [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-12 (work in progress), July 2019.

   [I-D.ietf-pce-stateful-path-protection]
              Ananthakrishnan, H., Sivabalan, S., Barth, C., Minei, I.,
              and M. Negi, "PCEP Extensions for Associating Working and
              Protection LSPs with Stateful PCE", draft-ietf-pce-
              stateful-path-protection-07 (work in progress), June 2019.

   [I-D.ietf-pce-association-diversity]
              Litkowski, S., Sivabalan, S., Barth, C., and M. Negi,
              "Path Computation Element Communication Protocol (PCEP)
              Extension for LSP Diversity Constraint Signaling", draft-
              ietf-pce-association-diversity-08 (work in progress), July
              2019.

Appendix A.  Example for Operator-configured Association Range

   Consider an association type T1 (which allows both dynamic and
   operator-configured association with a default range of <0x1000,
   0xffff>).  Consider that, because of need of the network, the PCE
   needs to create more dynamic associations and would like to change
   the association range to <0xbffe, 0xffff> instead.  During PCEP
   session establishment the PCE would advertise the new range, the PCC
   could skip advertising as the default values are used.  If a PCC is
   creating a dynamic association (with PCC as association source) it
   needs to pick a free association identifier for type T1 in the range
   of <0x1, 0x0fff> whereas if a PCE is creating a dynamic association
   (with PCE as association source) it needs to pick a free association



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   identifier from the range <0x1, 0xbffd>.  Similarly if an operator-
   configured association is manually configured with the PCC as
   association source, it should be from the range <0x1000, 0xffff>
   whereas if the PCE is association source, it should be from <0xbffe,
   0xffff>.  In case the association source is not a PCEP peer (for
   example an NMS system), then the default range of <0x1000, 0xffff> is
   considered.

Authors' Addresses

   Ina Minei
   Google, Inc.
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   US

   Email: inaminei@google.com


   Edward Crabbe
   Individual Contributor

   Email: edward.crabbe@gmail.com


   Siva Sivabalan
   Cisco Systems, Inc.
   170 West Tasman Dr.
   San Jose, CA  95134
   US

   Email: msiva@cisco.com


   Hariharan Ananthakrishnan
   Netflix

   Email: hari@netflix.com


   Dhruv Dhody
   Huawei
   Divyashree Techno Park, Whitefield
   Bangalore, KA  560066
   India

   Email: dhruv.ietf@gmail.com




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   Yosuke Tanaka
   NTT Communications Corporation
   Granpark Tower 3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   Email: yosuke.tanaka@ntt.com












































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