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Versions: (draft-sivabalan-pce-dste) 00 01 02 RFC 5455

     Network Working Group                           S. Sivabalan, Ed.
     Internet Draft                                          J. Parker
     Intended status: Standards Track                       S. Boutros
     Expires: April 15, 2008                       Cisco Systems, Inc.
                                                             K. Kumaki
                                                      KDDI Corporation
                                                      October 23, 2007
         Diff-Serv Aware Class Type Object for Path Computation Element
                             Communication Protocol
     Status of this Memo
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        This document specifies a CLASSTYPE object to support Diff-Serve
        Aware Traffic Engineering (DS-TE) where path computation is
        performed with an aid of Path Computation Element (PCE).
     Conventions used in this document
        The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
        "OPTIONAL" in this document are to be interpreted as described
        in RFC-2119.
     Table of Contents
        1. Introduction................................................2
        2. Terminology.................................................3
        3. CLASSTYPE object............................................3
        3.1. Object definition.........................................4
        3.2. Path Computation Request Message with CLASSTYPE object....5
        3.3. Handling of the CLASSTYPE object..........................5
        3.4. Determination of Traffic Engineering Class (TE-Class).....6
        3.5. Significance of Class-type and TE-Class...................6
        3.6. Error Codes for CLASSTYPE object..........................6
        4. Security Considerations.....................................7
        5. IANA Considerations.........................................7
        6. Acknowledgments.............................................7
        7. References..................................................7
        7.1. Normative References......................................7
        Author's Addresses.............................................8
        Intellectual Property Statement................................9
        Disclaimer of Validity.........................................9
     1. Introduction
        The Internet Draft [PCEP-ID] specifies the Path Computation
        Element communication Protocol (PCEP) for communications between
        a Path Computation Client(PCC) and a Path Computation Element
        (PCE), or between two PCEs, in compliance with [RFC4657].
        Differentiated Service aware MPLS Traffic Engineering (DS-TE)
        addresses the fundamental requirement to be able to enforce
        different bandwidth constraints for different classes of traffic
        and describes mechanisms to achieve per-class traffic
        engineering, rather than on an aggregate basis across all
        classes by enforcing Bandwidth Constraints (BCs) on different
        classes. Requirements for DS-TE and the associated protocol
        extensions are specified in [RFC3564] and [RFC4124]
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        As per [RFC4657], PCEP must support traffic class-type as an
        MPLS TE specific constraint. However, in the present form, PCEP
        [PCEP-ID] does not have the capability to specify the class-type
        in the path computation request.
        In this document, we define a new PCEP object called CLASSTYPE
        which carries the class-type of the TE LSP in the path
        computation request. During path computation, a PCE uses the
        class-type to identify the bandwidth constraint of the TE-LSP.
     2. Terminology
        CT: Class type: A set of Traffic Trunks governed by a set of
        bandwidth constraints. Used for the purpose of link bandwidth
        allocation, constraint based routing and admission control. A
        given Traffic Trunk belongs to the same CT on all links.
        DS-TE: Diff-Serv Aware Traffic Engineering.
        LSR: Label Switching Router.
        LSP: Label Switched Path.
        PCC: Path Computation Client: any client application requesting
        a path computation to be performed by a Path Computation
        PCE: Path Computation Element: an entity (component, application
        or network node) that is capable of computing a network path or
        route based on a network graph and applying computational
        PCEP Peer: an element involved in a PCEP session (i.e. a PCC or
        the PCE).
        TE-Class: A pair consisting of a class-type and a preemption
        priority allowed for that class type. An LSP transporting a
        Traffic Trunk from that class type can use that preemption
        priority as the setup priority, the holding priority, or both.
        TE LSP: Traffic Engineering Label Switched Path.
        Traffic Trunk: An aggregation of traffic flows of the same class
        (i.e. treated equivalently from the DS-TE perspective) which is
        placed inside a TE LSP.
     3. CLASSTYPE object
        The CLASSTYPE object is optional and is used to specify the
        class-type of a TE LSP. This object is meaningful only within
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        the path computation request, and is ignored in the path reply
        message. If the TE LSP for which path is to be computed belongs
        to Class 0, the path computation request MUST not contain the
        CLASSTYPE object. This allows backward compatibility with PCE
        that does not support CLASSTYPE object.
     3.1. Object definition
        The CLASSTYPE object contains a 32-bit word PCEP common object
        header defined in [PCEP-ID] followed by another 32-bit word
        object body 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
     | Object-Class  |   OT  |Res|P|I|   Object Length (bytes)       |
     |            Reserved                                     | CT  |
                       Figure 1 CLASSTYPE object format.
        The fields in the object common header are processed as
        specified in [PCEP-ID]. We explain these fields again for
        completion. For more details, please refer to [PCEP-ID].
        Object-Class is to be assigned by IANA (recommended value=16).
        Object-Type (OT) is to be assigned by IANA (recommended
        Res flags (2 bits). Reserved field. This field MUST be set to
        zero on transmission and MUST be ignored on receipt.
        P flag (1 bit): When the P flag is set, the CLASSTYPE object
        MUST be taken into account by the PCE. Conversely, when the P
        flag is cleared, the object is optional and the PCE is free to
        ignore it if not supported.
        I flag (1 bit): The PCE MAY include the ignored optional object
        in its reply and set the I flag to indicate that the optional
        object was ignored during path computation.
        Object Length (16 bits).  Specifies the total object length
        including the header, in bytes.  The Object Length field MUST
        always be a multiple of 4, and at least 4.  The maximum object
        content length is 65528 bytes.
        The CLASSTYPE object body contains the following fields:
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        CT: 3-bit field that indicates the class-type. Values allowed
        are 1, 2, ... , 7. Value of 0 is Reserved.
        Reserved: 29-bit reserved field. It MUST be set to zero on
        transmission and MUST be ignored on receipt.
     3.2. Path Computation Request Message with CLASSTYPE object
        The draft [PCEP-ID] specifies the object orders in which objects
        must be inserted in the PCEP messages. This document specifies
        that the CLASSTYPE object be inserted after the END-POINT
        objects as shown below:
        The format of a PCReq message is as follows:
           <PCReq Message>::= <Common Header>
              <request>::= <RP>
     3.3. Handling of the CLASSTYPE object
        If the LSP is associated with Class-Type N (1 <= N <= 7), the
        PCC originating the path computation request MUST include the
        CLASSTYPE object in the Path computation request message with
        the Class-Type (CT) field set to N.
        If a path computation request contains multiple CLASSTYPE
        objects, only the first one is meaningful; subsequent CLASSTYPE
        object(s) MUST be ignored and MUST NOT be forwarded.
        If the CLASSTYPE object is not present in the path computation
        request message, the LSR MUST associate the Class-Type 0 to the
        Path computation reply message MUST NOT include a CLASSTYPE
        object. If a PCE needs to forward a path computation request
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        containing the CLASSTYPE object to another PCE, it MUST store
        the class-type of the TE LSP in order to complete the path
        computation when the path computation reply arrives.
        A PCE receiving a path computation request message with the
        CLASSTYPE  object with P flag set that does not recognize the
        CLASSTYPE object MUST reject the entire PCEP message and MUST
        send a PCE error message with Error-Type="Unknown Object" or
        "Not supported Object" defined in [PCEP-ID].
        A PCE receiving a path computation request message with the
        CLASSTYPE object that recognizes the CLASSTYPE object, but
        does not support the particular Class-Type, MUST send a PCE
        error message towards the sender with the error type  "Diff-Serv
        aware TE Error" and an error value of "Unsupported Class-Type"
        (new error code provided below).
        A PCE receiving a path computation request message with the
        CLASSTYPE object that recognizes the CLASSTYPE object, but
        determines that the Class-Type value is not valid (i.e., Class
        Type value 0), MUST send a PCE error towards the sender with the
        error type "Diff-Serve aware TE Error" and an error value of
        "Invalid Class-Type value" (new error code provided below).
     3.4. Determination of Traffic Engineering Class (TE-Class)
        As specified in RFC4124, a CT and a Preemption priority map to a
        Traffic Engineering Class (TE-Class), and there can be up to 8
        TE-classes. The TE-class value is used to determine the
        unreserved bandwidth on the links during path computation. In
        the case of a PCE, the CT value carried in the CLASSTYPE object
        and the setup priority in the LSP Attribute (LSPA) object are
        used to determine the TE-class corresponding to the path
        computation request. If LSPA object is absent, the setup
        priority is assumed to be 0.
     3.5. Significance of Class-type and TE-Class
        To ensure coherent DS-TE operation, a PCE and a PCC should have
        a common understanding of a particular DS-TE classtype and TE-
        Class.  If a path computation request crosses an AS boundary,
        these should have global significance in all domains.
        Enforcement of this global significance is outside the scope of
        this document.
     3.6. Error Codes for CLASSTYPE object
        This document defines the following error type and values:
        Error-Type    Meaning
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           11         Diff-Serve aware TE Error
                      Error-value=1: unsupported class-type.
                      Error-value=2: invalid class-type.
                      Error-value=3: class-type and setup priority does
                       form a configured TE class.
     4. Security Considerations
        This document does not introduce new security issues.  The
        security considerations pertaining to PCEP [PCEP-ID] remain
     5. IANA Considerations
        IANA assigns value to PCEP parameters.  Each PCEP object has an
        Object-Class and an Object-Type. For the CLASSTYPE object, the
        suggested values for Object-Class and Object-Type are 16 and 1
     6. Acknowledgments
        The authors would like to thank Jean Philippe Vasseur for his
        valuable comments.
     7. References
     7.1. Normative References
        [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119, March 1997.
        [RSVP-TE] Awduche, D., Berger, L., Gan, D., Li, T.,Srinivasan,
                  V., and G. Swallow, "RSVP-TE: Extensions to RSVP for
                  LSP Tunnels", RFC 3209, December 2001.
         [RFC4124]Le Faucheur, F. and W. Lai, "Protocol Extensions for
                  Support of Diffserv-aware MPLS Traffic Engineering",
                  RFC 4124, June 2005.
        [PCEP-ID] Path Computation Element (PCE) communication  Protocol
                  (PCEP)", draft-ietf-pce-pcep-08.txt (work in
                  progress), February 2007.
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     7.2. Informative References
        [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element
                  (PCE) Communication Protocol Generic Requirements",
                  RFC 4657, September 2006.
        [RFC3564] Le Faucheur, F. and W. Lai, "Requirements for Support
                  of Differentiated Services-aware MPLS Traffic
                  Engineering", RFC 3564, July 2003.
     Author's Addresses
        Siva Sivabalan
        Cisco Systems, Inc.
        2000 Innovation Drive
        Kanata, Ontario, K2K 3E8
        Email: msiva@cisco.com
        Jon Parker
        Cisco Systems, Inc.
        2000 Innovation Drive
        Kanata, Ontario, K2K 3E8
        Email: jdparker@cisco.com
        Sami Boutros
        Cisco Systems, Inc.
        2000 Innovation Drive
        Kanata, Ontario, K2K 3E8
        Email: sboutros@cisco.com
     S. Sivabalan            Expires April 23, 2008            Page 8]
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        Kenji Kumaki
        KDDI Corporation
        Garden Air Tower Iidabashi, Chiyoda-ku
        Tokyo, 102-8460
        Email: ke-kumaki@kddi.com
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