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rfc:rfc7470

Internet Engineering Task Force (IETF) F. Zhang Request for Comments: 7470 Huawei Obsoletes: 7150 A. Farrel Category: Standards Track Juniper Networks ISSN: 2070-1721 March 2015

               Conveying Vendor-Specific Constraints
       in the Path Computation Element Communication Protocol

Abstract

 The Path Computation Element Communication Protocol (PCEP) is used to
 convey path computation requests and responses both between Path
 Computation Clients (PCCs) and Path Computation Elements (PCEs) and
 between cooperating PCEs.  In PCEP, the path computation requests
 carry details of the constraints and objective functions that the PCC
 wishes the PCE to apply in its computation.
 This document defines a facility to carry vendor-specific information
 in PCEP using a dedicated object and a new Type-Length-Value (TLV)
 that can be carried in any PCEP object that supports TLVs.
 This document obsoletes RFC 7150.  The only changes from that
 document are a clarification of the use of the new Type-Length-Value
 and the allocation of a different code point for the VENDOR-
 INFORMATION object.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7470.

Zhang & Farrel Standards Track [Page 1] RFC 7470 Vendor-Specific Constraints in PCE March 2015

Copyright Notice

 Copyright (c) 2015 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
 (http://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 ....................................................3
    1.1. Conventions Used in This Document ..........................4
 2. Procedures for the Vendor Information Object ....................5
    2.1. Backward Compatibility for the Vendor Information Object ...7
 3. Procedures for the Vendor Information TLV .......................7
    3.1. Backward Compatibility .....................................8
 4. Protocol Elements ...............................................8
 5. IANA Considerations .............................................9
    5.1. New PCEP Object ............................................9
    5.2. New PCEP TLV ...............................................9
 6. Management Considerations ......................................10
    6.1. Control of Function and Policy ............................10
    6.2. Information and Data Models ...............................10
    6.3. Liveness Detection and Monitoring .........................10
    6.4. Verifying Correct Operation ...............................10
    6.5. Requirements on Other Protocols and Functional Components .11
    6.6. Impact on Network Operation ...............................11
 7. Security Considerations ........................................11
 8. References .....................................................12
    8.1. Normative References ......................................12
    8.2. Informative References ....................................12
 Acknowledgements ..................................................14
 Contributors ......................................................14
 Authors' Addresses ................................................14

Zhang & Farrel Standards Track [Page 2] RFC 7470 Vendor-Specific Constraints in PCE March 2015

1. Introduction

 A Path Computation Element (PCE) is 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.  An architecture for the use of PCEs is defined in
 [RFC4655].
 The Path Computation Element Communication Protocol (PCEP) is defined
 in [RFC5440] to exchange path computation requests and responses
 between Path Computation Clients (PCCs) and PCEs.  It is also used
 between cooperating PCEs.
 Path computations performed by a PCE depend on a set of constraints
 indicated by the PCC.  These constraints include the endpoints of the
 path to compute (source and destination) and may include other simple
 constraints such as bandwidth requirements and metric maxima (for
 example, a maximum threshold for the hop count or the Traffic
 Engineering (TE) metric of the computed path).
 The PCE also needs to use an objective function to qualify the path
 it selects as meeting the requirements of the PCC.  The PCE may have
 a default objective function, but the PCC can also indicate which
 objective function it wants applied by placing an Objective Function
 object in the path computation request message [RFC5541].  A core set
 of objective functions to be supported in PCEP messages is defined in
 the base PCEP requirements [RFC4657], and [RFC5541] defines each of
 these functions as an abstract formula.
 The registry of codepoints used to indicate objective functions is
 managed by IANA and new assignments can be made according to "IETF
 Review" and "First Come First Served" policies [RFC5226].  PCE
 implementations may also choose to offer proprietary, vendor-specific
 objective functions, and there is scope for this within the codepoint
 registry created by [RFC5541] using the codepoints that are flagged
 as "Reserved for Private Use".
 Proprietary objective functions may operate on non-standard
 constraints or metrics.  The PCEP METRIC Object defined in [RFC5440]
 has scope for the definition of new, standardized metrics, but no
 facility for the definition of vendor-specific metrics.  At the same
 time, there is no mechanism in PCEP for carrying other, more complex,
 vendor-specific information.
 This document defines a new PCEP object, the Vendor Information
 object that can be used to carry arbitrary, proprietary information
 such as vendor-specific constraints.

Zhang & Farrel Standards Track [Page 3] RFC 7470 Vendor-Specific Constraints in PCE March 2015

 This document also defines a new PCEP TLV, the VENDOR-INFORMATION-TLV
 that can be used to carry arbitrary information within any existing
 or future PCEP object that supports TLVs.
 It should be noted that by the very definition of "vendor-specific",
 the inclusion of either a Vendor Information object or the VENDOR-
 INFORMATION-TLV implies an inability to interoperate at a functional
 level with implementations from other vendors unless there is some
 cooperation agreement between vendors.  Sections 2.1 and 3.1 discuss
 backward compatibility, which indicates how these protocol constructs
 are handled by implementations that do not support them at all, while
 text in Sections 2 and 3 describe how implementations handle the
 constructs if they understand them, but do not support the embedded
 Enterprise Number that indicates to which vendor the constructs
 apply.
 When vendor-specific information is used by an implementation, the
 vendor is encouraged to document the meaning of the information to
 encourage wider use and implementation.  In particular, when there is
 more general interest in a vendor-specific extension, the vendor is
 encouraged to bring it to the IETF for standardization as a regular
 protocol construct, thereby moving it out of the vendor-specific
 space.
 This document obsoletes RFC 7150 [RFC7150], making two changes to
 that document:
  1. Clarification that the TLV is available for use in any PCEP object

(existing or future) that supports TLVs.

  1. The allocation of a different code point for the

VENDOR-INFORMATION object. This change became necessary because

    of an inadvertent clash with codepoints used in an Internet-Draft
    that had been deployed without IANA allocation.  The PCE working
    group has conducted a survey of implementations and deployments of
    RFC 7150 and considers that this change is safe and does not harm
    early implementers of RFC 7150.

1.1. Conventions Used in This Document

 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
 [RFC2119].

Zhang & Farrel Standards Track [Page 4] RFC 7470 Vendor-Specific Constraints in PCE March 2015

2. Procedures for the Vendor Information Object

 A PCC that wants to convey proprietary or vendor-specific constraints
 or metrics to a PCE does so by including a Vendor Information object
 in the PCReq message.  The contents and format of the object are
 described in Section 4, but it is important to note that the object
 includes an Enterprise Number that is a unique identifier of an
 organization responsible for the definition of the content and
 meaning of the object.
 A PCE that receives a PCReq message containing a Vendor Information
 object MUST act according to the P flag in the object header.  That
 is, if the P flag is set, the object will be treated as mandatory and
 the request will either be processed using the contents of the object
 or be rejected as defined in [RFC5440] (see also Section 2.1).  If
 the P flag is clear, then, as defined in [RFC5440], the object may be
 used by the PCE or may be ignored.  The PCC sets the P flag according
 to how it wishes the request to be processed.
 The PCE determines how to interpret the information in the Vendor
 Information object by examining the Enterprise Number it contains.
 An implementation that supports the Vendor Information object, but
 receives one carrying an Enterprise Number that it does not support
 MUST act according to the P flag in the object.  That is, if the P
 flag is set, the PCE MUST reject the PCReq as defined in [RFC5440] by
 sending an Error message with Error-Type="Not supported Object" along
 with the corresponding Vendor Information object.
 The Vendor Information object is OPTIONAL in a PCReq message.
 Multiple instances of the object MAY be used on a single PCReq
 message, and each MUST be treated according to its P-bit setting.
 Different instances of the object can have different Enterprise
 Numbers.
 The object can be present in the PCReq message to enable it to apply
 to a single path computation request or to a set of synchronized
 requests.  This usage mirrors the usage of the Objective Function
 object [RFC5541].  Thus, the PCReq message based on [RFC6006] is
 encoded as follows using the syntax described in [RFC5511].

Zhang & Farrel Standards Track [Page 5] RFC 7470 Vendor-Specific Constraints in PCE March 2015

 <PCReq Message> ::= <Common Header>
                     [<svec_list>]
                     <request-list>
 where
     <svec-list> ::= <SVEC>
                     [<OF>]
                     [<GC>]
                     [<XRO>]
                     [<metric-list>]
                     [<vendor-info-list>]
                     [<svec-list>]
     <metric-list> ::= <METRIC>
                       [<metric-list>]
     <vendor-info-list> ::= <VENDOR-INFORMATION>
                            [<vendor-info-list>]
     <request-list> ::= <request>
                        [<request-list>]
     <request> ::= <RP>
                   [<vendor-info-list>]
                   <end-point-rro-pair-list>
                   [<LSPA>]
                   [<BANDWIDTH>]
                   [<metric-list>]
                   [<OF>]
                   [<RRO>]
                   [<IRO>]
                   [<LOAD-BALANCING>]
 where
     <end-point-rro-pair-list> ::= <END-POINTS>
                                   [<RRO-List>]
                                   [<BANDWIDTH>]
                                   [<vendor-info-list>]
                                   [<end-point-rro-pair-list>]
     <RRO-List> ::= <RRO> [<BANDWIDTH>] [<RRO-List>]
     <metric-list> ::= <METRIC> [<metric-list>]

Zhang & Farrel Standards Track [Page 6] RFC 7470 Vendor-Specific Constraints in PCE March 2015

 The Vendor Information object can be included in a PCRep message in
 exactly the same way as any other object as defined in [RFC5440].
 Thus, the PCRep is encoded as follows:
   <PCRep Message> ::= <Common Header>
                       <response>
   <response> ::= <RP>
                  [<vendor-info-list>]
                  [<end-point-path-pair-list>]
                  [<NO-PATH>]
                  [<attribute-list>]
 where:
    <end-point-path-pair-list> ::=
                   [<END-POINTS>]
                   <path>
                   [<vendor-info-list>]
                   [<end-point-path-pair-list>]
   <path> ::= (<ERO>|<SERO>) [<path>]
   <attribute-list> ::= [<OF>]
                        [<LSPA>]
                        [<BANDWIDTH>]
                        [<metric-list>]
                        [<IRO>]

2.1. Backward Compatibility for the Vendor Information Object

 A legacy implementation that does not recognize the Vendor
 Information object will act according to the procedures set out in
 [RFC5440].  If the P flag is set in the object, the message will be
 rejected using a PCErr message with an Error Type of 3 ("Unknown
 Object").  If the P flag is not set, the object can safely be ignored
 by the recipient.

3. Procedures for the Vendor Information TLV

 The Vendor Information TLV can be used to carry vendor-specific
 information that applies to a specific PCEP object by including the
 TLV in the object.

Zhang & Farrel Standards Track [Page 7] RFC 7470 Vendor-Specific Constraints in PCE March 2015

 The PCE determines how to interpret the Vendor Information TLV by
 examining the Enterprise Number it contains.  If the Enterprise
 Number is unknown to the PCE, it MUST treat the Vendor Information
 TLV as an unknown TLV and handle it as described in [RFC5440] (see
 also Section 3.1).
 Further specifications are needed to define the position and meaning
 of the Vendor Information TLV for specific PCEP objects.

3.1. Backward Compatibility

 A legacy implementation that does not recognize the Vendor
 Information TLV in an object will act according to the procedures set
 out in [RFC5440].  As described in Section 7.1 of [RFC5440],
 unrecognized TLVs MUST be ignored.

4. Protocol Elements

 The Vendor Information object and TLV conform to the format for PCEP
 objects and TLVs defined in [RFC5440].
 VENDOR-INFORMATION Object-Class 34
 VENDOR-INFORMATION Object-Type 1
 VENDOR-INFORMATION-TLV Type 7
 The format of the VENDOR-INFORMATION object and the format of the
 VENDOR-INFORMATION-TLV are the same and are as shown in Figure 1.
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Enterprise Number                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                 Enterprise-Specific Information               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 1 : Format of the Vendor Information Object and TLV
 Enterprise Number
    A unique identifier of an organization encoded as a 32-bit
    integer.  Enterprise Numbers are assigned by IANA and managed
    through an IANA registry [RFC2578].

Zhang & Farrel Standards Track [Page 8] RFC 7470 Vendor-Specific Constraints in PCE March 2015

 Enterprise-Specific Information
    The detailed enterprise-specific constraint information carried by
    the object.  The format and interpretation of this information is
    a matter for the enterprise identified by the Enterprise Number.
    Such formats and interpretation may be published by the enterprise
    (possibly through an Informational RFC or through commercial
    documentation) so that PCCs or PCEs that are not part of the
    organization can use the information.

5. IANA Considerations

 IANA maintains a registry of PCEP parameters called the "Path
 Computation Element Protocol (PCEP) Numbers".

5.1. New PCEP Object

 IANA had previously allocated the value 32 from the "PCEP Objects"
 subregistry for use as the VENDOR-INFORMATION object.  IANA has
 released that value and marked it as "Unassigned".
 IANA has assigned a new value as follows.
 Object-Class Value     Name                               Reference
     34                 VENDOR-INFORMATION                 RFC 7470
            Object-Type
              0: Unassigned
              1: Vendor-Specific Constraints               RFC 7470
              2-15: Unassigned

5.2. New PCEP TLV

 IANA had made an allocation from the "PCEP TLV Type Indicators"
 subregistry, where RFC 7150 was the reference.  IANA has updated the
 reference as follows to point to this document.
 Value       Description                                   Reference
   7         VENDOR-INFORMATION-TLV                        RFC 7470

Zhang & Farrel Standards Track [Page 9] RFC 7470 Vendor-Specific Constraints in PCE March 2015

6. Management Considerations

 This section follows the guidance of [RFC5706] and [RFC6123].

6.1. Control of Function and Policy

 A PCEP implementation SHOULD allow configuring of various parameters
 as described in [RFC5440].  A PCC implementation that uses vendor-
 specific information MAY make the use of this information
 configurable either across the whole PCC, per PCE that the PCC uses,
 or per path computation request.  A PCE that supports vendor-specific
 information MAY make the support of this information configurable,
 and MAY allow configuration of policies for the use of the
 information.

6.2. Information and Data Models

 A PCEP MIB module is defined in [RFC7420] that describes managed
 objects for modeling of PCEP communications.
 It is NOT RECOMMENDED that standard MIB modules be extended to
 include detailed information about the content of the Vendor
 Information object or TLV.  However, the standard MIB module MAY be
 extended to report the use of the Vendor Information object or TLV
 and the Enterprise Numbers that the objects and TLVs contain.

6.3. Liveness Detection and Monitoring

 This document makes no change to the basic operation of PCEP, so
 there are no changes to the requirements for liveness detection and
 monitoring set out in [RFC4657] and [RFC5440].

6.4. Verifying Correct Operation

 This document makes no change to the basic operation of PCEP, so
 there are no changes to the requirements or techniques for monitoring
 the correct operation of the protocol out in [RFC4657] and [RFC5440].
 Note that "correct operation" in this context refers to the operation
 of the protocol itself and not to the operation of the computation
 algorithms which are out of scope for all PCEP work.
 Mechanisms for verifying the correct operation of computation
 algorithms might involve comparing the results returned by more than
 one PCE.  Scope for this might be limited by the use of vendor
 information unless multiple PCEs support the same set of vendor
 information.

Zhang & Farrel Standards Track [Page 10] RFC 7470 Vendor-Specific Constraints in PCE March 2015

6.5. Requirements on Other Protocols and Functional Components

 This document does not place any new requirements on other network
 components or protocols.  However, it may be beneficial to consider
 whether a PCE should advertise the Enterprise Numbers and vendor
 information it supports.  This advertisement could be within PCE
 Discovery [RFC5088] [RFC5089] or through extensions to PCEP
 [RFC5440].
 Extensions for discovery and advertisement are outside the scope of
 this document.

6.6. Impact on Network Operation

 The availability of vendor information in PCEP messages may
 facilitate more complex and detailed path computations that may
 enhance the way in which the network is operated.
 On the other hand, the presence of additional vendor-specific
 information in PCEP messages may congest the operation of the
 protocol especially if the PCE does not support the information
 supplied by the PCC.  Thus, a PCC SHOULD monitor the capabilities of
 a PCE either by discovery mechanisms as described in Section 6.5 or
 through the receipt of negative responses.  A PCC SHOULD NOT include
 vendor information in a PCReq message to a PCE that it believes does
 not support the information and that will not forward the request to
 some other PCE that does support the information.

7. Security Considerations

 The protocol extensions defined in this document do not substantially
 change the nature of PCEP.  Therefore, the security considerations
 set out in [RFC5440] apply unchanged.  Note that further security
 considerations for the use of PCEP over TCP are presented in
 [RFC6952].
 Operators should note that an attack on PCEP may involve making PCEP
 messages as large as possible in order to consume bandwidth and
 processing power.  The Vendor Information object and TLV may provide
 a vector for this type of attack.  It may be protected against by
 using the authentication and integrity procedures described in
 [RFC5440].

Zhang & Farrel Standards Track [Page 11] RFC 7470 Vendor-Specific Constraints in PCE March 2015

8. References

8.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC5440]  Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation
            Element (PCE) Communication Protocol (PCEP)", RFC 5440,
            March 2009, <http://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, April 2009,
            <http://www.rfc-editor.org/info/rfc5511>.
 [RFC6006]  Zhao, Q., Ed., King, D., Ed., Verhaeghe, F., Takeda, T.,
            Ali, Z., and J. Meuric, "Extensions to the Path
            Computation Element Communication Protocol (PCEP) for
            Point-to-Multipoint Traffic Engineering Label Switched
            Paths", RFC 6006, September 2010,
            <http://www.rfc-editor.org/info/rfc6006>.

8.2. Informative References

 [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
            Schoenwaelder, Ed., "Structure of Management Information
            Version 2 (SMIv2)", STD 58, RFC 2578, April 1999,
            <http://www.rfc-editor.org/info/rfc2578>.
 [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
            Computation Element (PCE)-Based Architecture", RFC 4655,
            August 2006, <http://www.rfc-editor.org/info/rfc4655>.
 [RFC4657]  Ash, J., Ed., and J. Le Roux, Ed., "Path Computation
            Element (PCE) Communication Protocol Generic
            Requirements", RFC 4657, September 2006,
            <http://www.rfc-editor.org/info/rfc4657>.
 [RFC5088]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
            Zhang, "OSPF Protocol Extensions for Path Computation
            Element (PCE) Discovery", RFC 5088, January 2008,
            <http://www.rfc-editor.org/info/rfc5088>.

Zhang & Farrel Standards Track [Page 12] RFC 7470 Vendor-Specific Constraints in PCE March 2015

 [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
            Zhang, "IS-IS Protocol Extensions for Path Computation
            Element (PCE) Discovery", RFC 5089, January 2008,
            <http://www.rfc-editor.org/info/rfc5089>.
 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008, <http://www.rfc-editor.org/info/rfc5226>.
 [RFC5541]  Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
            Objective Functions in the Path Computation Element
            Communication Protocol (PCEP)", RFC 5541, June 2009,
            <http://www.rfc-editor.org/info/rfc5541>.
 [RFC5706]  Harrington, D., "Guidelines for Considering Operations and
            Management of New Protocols and Protocol Extensions", RFC
            5706, November 2009,
            <http://www.rfc-editor.org/info/rfc5706>.
 [RFC6123]  Farrel, A., "Inclusion of Manageability Sections in Path
            Computation Element (PCE) Working Group Drafts", RFC 6123,
            February 2011, <http://www.rfc-editor.org/info/rfc6123>.
 [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
            BGP, LDP, PCEP, and MSDP Issues According to the Keying
            and Authentication for Routing Protocols (KARP) Design
            Guide", RFC 6952, May 2013,
            <http://www.rfc-editor.org/info/rfc6952>.
 [RFC7150]  Zhang, F. and A. Farrel, "Conveying Vendor-Specific
            Constraints in the Path Computation Element Communication
            Protocol", RFC 7150, March 2014,
            <http://www.rfc-editor.org/info/rfc7150>.
 [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, December 2014,
            <http://www.rfc-editor.org/info/rfc7420>.

Zhang & Farrel Standards Track [Page 13] RFC 7470 Vendor-Specific Constraints in PCE March 2015

Acknowledgements

 Thanks to Meral Shirazipour, Ramon Casellas, Cyril Margaria, Dhruv
 Dhody, Julien Meuric, and Robert Sparks for review and comments on
 the work that became RFC 7150.
 Thanks to Robert Varga for raising the issue of the clashing code
 point and to Dhruv Dhody for helping clarify the use of the TLV.

Contributors

 Greg Bernstein
 Grotto Networking
 EMail: gregb@grotto-networking.com
 Ina Minei
 Juniper Networks
 EMail: ina@juniper.net

Authors' Addresses

 Adrian Farrel
 Juniper Networks
 EMail: adrian@olddog.co.uk
 Fatai Zhang
 Huawei Technologies
 EMail: zhangfatai@huawei.com

Zhang & Farrel Standards Track [Page 14]

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