Movatterモバイル変換

Internet Engineering Task Force (IETF)                          F. ZhangRequest for Comments: 7150                                        HuaweiCategory: Standards Track                                      A. FarrelISSN: 2070-1721                                         Juniper Networks                                                              March 2014Conveying Vendor-Specific Constraints in the PathComputation Element Communication ProtocolAbstract   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-Variable that   can be carried in any existing PCEP 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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7150.Zhang & Farrel               Standards Track                    [Page 1]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.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-specificZhang & Farrel               Standards Track                    [Page 2]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014   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.   This document also defines a new PCEP TLV, the VENDOR-INFORMATION-TLV   that can be used to carry arbitrary information within any 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.  Sections2.1 and3.1 discuss   backward compatibility, which indicates how these protocol constructs   are handled by implementations that do not support them at all, while   text in Sections2 and3 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 moving it out of the vendor-specific space.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 3]

RFC 7150           Vendor-Specific Constraints in PCE         March 20142.  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 inSection 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 alsoSection 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 4]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014   <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>]   The Vendor Information object can be included in a PCRep message in   exactly the same way as any other object as defined in [RFC5440].Zhang & Farrel               Standards Track                    [Page 5]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014   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.   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   alsoSection 3.1).Zhang & Farrel               Standards Track                    [Page 6]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014   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 inSection 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 32   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].   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 enterpriseZhang & Farrel               Standards Track                    [Page 7]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014      (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 has made an allocation from the "PCEP Objects" subregistry as   follows.   Object-Class Value     Name                               Reference       32                 VENDOR-INFORMATION                 [RFC7150]              Object-Type                0: Unassigned                1: Vendor-Specific Constraints               [RFC7150]                2-255: Unassigned5.2.  New PCEP TLV   IANA has made an allocation from the "PCEP TLV Type Indicators"   subregistry as follows.   Value       Description                                   Reference     7         VENDOR-INFORMATION-TLV                        [RFC7150]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.Zhang & Farrel               Standards Track                    [Page 8]

RFC 7150           Vendor-Specific Constraints in PCE         March 20146.2.  Information and Data Models   A PCEP MIB module is defined in [PCE-MIB] 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.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.Zhang & Farrel               Standards Track                    [Page 9]

RFC 7150           Vendor-Specific Constraints in PCE         March 20146.6.  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 inSection 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].8.  References8.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC5440]  Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation              Element (PCE) Communication Protocol (PCEP)",RFC 5440,              March 2009.   [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax              Used to Form Encoding Rules in Various Routing Protocol              Specifications",RFC 5511, April 2009.Zhang & Farrel               Standards Track                   [Page 10]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014   [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 2010.8.2.  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.   [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path              Computation Element (PCE)-Based Architecture",RFC 4655,              August 2006.   [RFC4657]  Ash, J., Ed., and J. Le Roux, Ed., "Path Computation              Element (PCE) Communication Protocol Generic              Requirements",RFC 4657, September 2006.   [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.   [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.   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an              IANA Considerations Section in RFCs",BCP 26,RFC 5226,              May 2008.   [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.   [RFC5706]  Harrington, D., "Guidelines for Considering Operations and              Management of New Protocols and Protocol Extensions",RFC5706, November 2009.   [RFC6123]  Farrel, A., "Inclusion of Manageability Sections in Path              Computation Element (PCE) Working Group Drafts",RFC 6123,              February 2011.Zhang & Farrel               Standards Track                   [Page 11]

RFC 7150           Vendor-Specific Constraints in PCE         March 2014   [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.   [PCE-MIB]  Koushik, A., Stephan, E., Zhao, Q., King, D., and J.              Hardwick, "Path Computation Element Protocol (PCEP)              Management Information Base", Work in Progress, February              2014.9.  Acknowledgements   Thanks to Meral Shirazipour, Ramon Casellas, Cyril Margaria, Dhruv   Dhody, Julien Meuric, and Robert Sparks for review and comments.10.  Contributors   Greg Bernstein   Grotto Networking   EMail: gregb@grotto-networking.com   Ina Minei   Juniper Networks   EMail: ina@juniper.netAuthors' Addresses   Adrian Farrel   Juniper Networks   EMail: adrian@olddog.co.uk   Fatai Zhang   Huawei Technologies   EMail: zhangfatai@huawei.comZhang & Farrel               Standards Track                   [Page 12]