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rfc:rfc7074

Internet Engineering Task Force (IETF) L. Berger Request for Comments: 7074 LabN Updates: 3471, 4202, 4203, 5307 J. Meuric Category: Standards Track Orange ISSN: 2070-1721 November 2013

Revised Definition of the GMPLS Switching Capability and Type Fields

Abstract

 GMPLS provides control for multiple switching technologies and for
 hierarchical switching within a technology.  GMPLS routing and
 signaling use common values to indicate the type of switching
 technology.  These values are carried in routing protocols via the
 Switching Capability field, and in signaling protocols via the
 Switching Type field.  While the values used in these fields are the
 primary indicators of the technology and hierarchy level being
 controlled, the values are not consistently defined and used across
 the different technologies supported by GMPLS.  This document is
 intended to resolve the inconsistent definition and use of the
 Switching Capability and Type fields by narrowly scoping the meaning
 and use of the fields.  This document updates all documents that use
 the GMPLS Switching Capability and Types fields, in particular RFCs
 3471, 4202, 4203, and 5307.

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/rfc7074.

Berger & Meuric Standards Track [Page 1] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

Copyright Notice

 Copyright (c) 2013 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.

1. Introduction

 Generalized Multiprotocol Label Switching (GMPLS) provides control
 for multiple switching technologies.  It also supports hierarchical
 switching within a technology.  The original GMPLS Architecture, per
 [RFC3945], included support for five types of switching capabilities.
 An additional type was also defined in [RFC6002].  The switching
 types defined in these documents include:
 1. Packet Switch Capable (PSC)
 2. Layer-2 Switch Capable (L2SC)
 3. Time-Division Multiplex Capable (TDM)
 4. Lambda Switch Capable (LSC)
 5. Fiber-Switch Capable (FSC)
 6. Data Channel Switching Capable (DCSC)
 Support for the original types was defined for routing in [RFC4202],
 [RFC4203], and [RFC5307], where the types were represented in the
 Switching Capability (Switching Cap) field.  In general, hierarchy
 within a type is addressed in a type-specific fashion, and a single
 Switching Capability field value is defined per type.  The exception
 to this is PSC, which was assigned four values to indicate four
 levels of hierarchy: PSC-1, PSC-2, PSC-3, and PSC-4.  The same values
 used in routing are defined for signaling in [RFC3471], and are
 carried in the Switching Type field.  Following the IANA registry, we
 refer to the values used in the routing Switching Capability field
 and signaling Switching Type field as Switching Types.

Berger & Meuric Standards Track [Page 2] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

 In general, a Switching Type does not indicate a specific data-plane
 technology; this needs to be inferred from context.  For example,
 L2SC was defined to cover Ethernet and ATM, and TDM was defined to
 cover both SONET/SDH [RFC4606] and G.709 [RFC4328].  The basic
 assumption was that different technologies of the same type would
 never operate within the same control, i.e., signaling and routing
 domains.
 The past approach in assignment of Switching Types has proven to be
 problematic from two perspectives.  The first issue is that some
 examples of switching technologies have different levels of switching
 that can be performed within the same technology.  For example, there
 are multiple types of Ethernet switching that may occur within a
 provider network.  The second issue is that the Switching Capability
 field value is used in Interior Gateway Protocols (IGPs) to indicate
 the format of the Switching Capability-specific information (SCSI)
 field, and that an implicit mapping of type to SCSI format is
 impractical for implementations that support multiple switching
 technologies.  These issues led to the introduction of two new types
 for Ethernet in [RFC6004] and [RFC6060], namely:
    7. Ethernet Virtual Private Line (EVPL)
    8. 802_1 PBB-TE (Provider Backbone Bridge Traffic Engineering)
 An additional value is also envisioned to be assigned in support of
 G.709v3 by [GMPLS-G709] in order to disambiguate the format of the
 SCSI field.
 While a common representation of hierarchy levels within a switching
 technology certainly fits the design objectives of GMPLS, the
 definition of multiple PSC Switching Types has also proven to be of
 little value.  Notably, there are no known uses of PSC-2, PSC-3, and
 PSC-4.
 This document proposes to resolve such inconsistent definitions and
 uses of the Switching Types by reducing the scope of the related
 fields and narrowing their use.  In particular, this document
 deprecates the use of the Switching Types as an identifier of
 hierarchy levels within a switching technology and limits its use to
 the identification of a per-switching technology SCSI field format.
 This document updates all documents that use the GMPLS Switching
 Capability and Switching Type fields, in particular RFCs 3471, 4202,
 4203, and 5307.

Berger & Meuric Standards Track [Page 3] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

1.1. Current Switching Type Definition

 The Switching Type values are carried in both routing and signaling
 protocols.  Values are identified in IANA's "Generalized Multi-
 Protocol Label Switching (GMPLS) Signaling Parameters" registry,
 which is currently located at <http://www.iana.org/assignments/
 gmpls-sig-parameters/>.
 For routing, a common information element is defined to carry
 Switching Type values for both OSPF and IS-IS routing protocols in
 [RFC4202].  Per [RFC4202], Switching Type values are carried in a
 Switching Capability (Switching Cap) field in an Interface Switching
 Capability Descriptor.  This information shares a common formatting
 in both OSPF as defined by [RFC4203] and in IS-IS as defined by
 [RFC5307]:
     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | Switching Cap |   Encoding    |           Reserved            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   ...
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        Switching Capability-specific information              |
    |                  (variable)                                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ...
    The content of the Switching Capability-specific information field
    depends on the value of the Switching Capability field.
 Similarly, the Switching Type field is defined as part of a common
 format for use by GMPLS signaling protocols in [RFC3471] and is used
 by [RFC3473]:
     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | LSP Enc. Type |Switching Type |             G-PID             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    Switching Type: 8 bits
       Indicates the type of switching that should be performed on a
       particular link.  This field is needed for links that advertise
       more than one type of switching capability.  This field should

Berger & Meuric Standards Track [Page 4] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

       map to one of the values advertised for the corresponding link
       in the routing Switching Capability Descriptor ...

1.2. Conventions Used In This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

2. Revised Switching Type Definition

 This document modifies the definition of Switching Type.  The
 definitions are slightly different for routing and signaling and are
 described in the following sections.

2.1. Routing – Switching Cap Field

 For routing [RFC4202] [RFC4203] [RFC5307], the following definition
 should be used for Switching Cap field:
    The Switching Cap field indicates the type of switching being
    advertised via GMPLS Switching Type values.  A different Switching
    Type value SHOULD be used for each data-plane technology, even
    when those technologies share the same type of multiplexing or
    switching.  For example, Time Division Multiplexing (TDM)
    technologies that have different multiplexing structures, such as
    Synchronous Digital Hierarchy (SDH) [G.707] and Optical Transport
    Network (OTN) [G.709], should use two different Switching Types.
    As the format of the Switching Capability-specific information
    field is dependent on the value of this field, a different
    Switching Type value MUST be used to differentiate between
    different Switching Capability-specific information field formats.
    This definition does not modify the format of the Interface
    Switching Capability Descriptor.
 Note that from a practical standpoint, this means that any time a new
 switching technology might use a different Switching Capability-
 specific information field format, a new Switching Type SHOULD be
 used.

Berger & Meuric Standards Track [Page 5] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

2.2. Signaling – Switching Type Field

 For signaling [RFC3471], which is used by [RFC3473], the following
 definition should be used for the Switching Type field:
    Indicates the type of switching that should be performed on a
    particular link via GMPLS Switching Type values.  This field maps
    to one of the values advertised for the corresponding link in the
    routing Switching Capability Descriptor, see [RFC4203] and
    [RFC5307].
 Note that from a practical standpoint, there is no change in the
 definition of this field.

2.3. Assigned Switching Types

 This document deprecates the following Switching Types:
    Value                 Name
      2       Packet-Switch Capable-2 (PSC-2)
      3       Packet-Switch Capable-3 (PSC-3)
      4       Packet-Switch Capable-4 (PSC-4)
    These values SHOULD be treated as unsupported types and, in the
    case of signaling, processed according to Section 2.1.1 of
    [RFC3473].

3. Compatibility

 For existing implementations, the primary impact of this document is
 deprecating the use of PSC-2, 3, and 4.  At the time of publication,
 there are no known deployments (or even implementations) that make
 use of these values, so there are no compatibility issues for current
 routing and signaling implementations.

4. Security Considerations

 This document impacts the values carried in a single field in
 signaling and routing protocols.  As no new protocol formats or
 mechanisms are defined, there are no particular security implications
 raised by this document.
 For a general discussion on MPLS- and GMPLS-related security issues,
 see the MPLS/GMPLS security framework [RFC5920].

Berger & Meuric Standards Track [Page 6] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

5. IANA Considerations

 IANA has deprecated some values and redefined the related values in
 the "IANA-GMPLS-TC-MIB" definitions.  In particular, the Switching
 Types portion of the "Generalized Multi-Protocol Label Switching
 (GMPLS) Signaling Parameters" registry been revised to read:
    Switching Types
       Registration Procedures
    Standards Action
       Reference
               [RFC3471][RFC4328][This Document]
        Value                  Name                  Reference
          0    Unassigned
          1    Packet-Switch Capable-1 (PSC-1)       [RFC3471]
          2    Deprecated                            [This Document]
          3    Deprecated                            [This Document]
          4    Deprecated                            [This Document]
        5-29   Unassigned
         30    Ethernet Virtual Private Line (EVPL)  [RFC6004]
        31-39  Unassigned
         40    802_1 PBB-TE                          [RFC6060]
        41-50  Unassigned
         51    Layer-2 Switch Capable (L2SC)         [RFC3471]
        52-99  Unassigned
         100   Time-Division-Multiplex Capable (TDM) [RFC3471]
       101-124 Unassigned
         125   Data Channel Switching Capable (DCSC) [RFC6002]
       126-149 Unassigned
         150   Lambda-Switch Capable (LSC)           [RFC3471]
       151-199 Unassigned
         200   Fiber-Switch Capable (FSC)            [RFC3471]
       201-255 Unassigned
 A parallel change to IANA-GMPLS-TC-MIB was also made. In particular,
 under IANAGmplsSwitchingTypeTC a reference to this document has been
 added as item 3.  The following changes have also been made to the
 related values:
        psc2(2),      -- Deprecated [This Document]
        psc3(3),      -- Deprecated [This Document]
        psc4(4),      -- Deprecated [This Document]

Berger & Meuric Standards Track [Page 7] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

6. Acknowledgments

 We thank John Drake for highlighting the current inconsistent
 definitions associated with the Switching Capability and Type fields.
 Daniele Ceccarelli and Adrian Farrel provided valuable feedback on
 this document.

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.
 [RFC3471]    Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description", RFC
              3471, January 2003.
 [RFC4202]    Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
              Extensions in Support of Generalized Multi-Protocol
              Label Switching (GMPLS)", RFC 4202, October 2005.
 [RFC4203]    Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, October 2005.
 [RFC5307]    Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS
              Extensions in Support of Generalized Multi-Protocol
              Label Switching (GMPLS)", RFC 5307, October 2008.

7.2. Informative References

 [G.707]      ITU-T Recommendation G.707/Y.1322 (2007), "Network node
              interface for the synchronous digital hierarchy (SDH)".
 [G.709]      ITU-T Recommendation G.709/Y.1331 (2009), "Interfaces
              for the Optical Transport Network (OTN)".
 [GMPLS-G709] Zhang, F., Li, D., Li, H., Belotti, S., and D.
              Ceccarelli, "Framework for GMPLS and PCE Control of
              G.709 Optical Transport Networks", Work in Progress,
              September 2013.
 [RFC3473]    Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation
              Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
              3473, January 2003.

Berger & Meuric Standards Track [Page 8] RFC 7074 GMPLS Switching and Type Fields Revision November 2013

 [RFC3945]    Mannie, E., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Architecture", RFC 3945, October 2004.
 [RFC4328]    Papadimitriou, D., Ed., "Generalized Multi-Protocol
              Label Switching (GMPLS) Signaling Extensions for G.709
              Optical Transport Networks Control", RFC 4328, January
              2006.
 [RFC4606]    Mannie, E. and D. Papadimitriou, "Generalized
              Multi-Protocol Label Switching (GMPLS) Extensions for
              Synchronous Optical Network (SONET) and Synchronous
              Digital Hierarchy (SDH) Control", RFC 4606, August 2006.
 [RFC5920]    Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.
 [RFC6002]    Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Data
              Channel Switching Capable (DCSC) and Channel Set Label
              Extensions", RFC 6002, October 2010.
 [RFC6004]    Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS)
              Support for Metro Ethernet Forum and G.8011 Ethernet
              Service Switching", RFC 6004, October 2010.
 [RFC6060]    Fedyk, D., Shah, H., Bitar, N., and A. Takacs,
              "Generalized Multiprotocol Label Switching (GMPLS)
              Control of Ethernet Provider Backbone Traffic
              Engineering (PBB-TE)", RFC 6060, March 2011.

8. Authors' Addresses

 Lou Berger
 LabN Consulting, L.L.C.
 Phone: +1 301 468 9228
 EMail: lberger@labn.net
 Julien Meuric
 Orange
 Research & Development
 2, Avenue Pierre Marzin
 22307 Lannion Cedex -- France
 Phone: +33 2 96 05 28 28
 EMail: julien.meuric@orange.com

Berger & Meuric Standards Track [Page 9]

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