Revised Definition of the GMPLS Switching Capability and Type Fields
RFC 7074

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.

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Copyright Notice

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   document authors.  All rights reserved.

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   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.

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   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.

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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

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         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.

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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].

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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]

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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.

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   [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

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