





Internet Engineering Task Force (IETF)                     D. Ceccarelli
Request for Comments: 8258                                      Ericsson
Category: Standards Track                                      L. Berger
ISSN: 2070-1721                                  LabN Consulting, L.L.C.
                                                            October 2017


                 Generalized SCSI: A Generic Structure
          for Interface Switching Capability Descriptor (ISCD)
            Switching Capability Specific Information (SCSI)

Abstract

   This document defines a generic information structure for information
   carried in routing protocol Interface Switching Capability Descriptor
   (ISCD) Switching Capability Specific Information (SCSI) fields.  This
   "Generalized SCSI" can be used with routing protocols that define
   GMPLS ISCDs and any specific technology.  This document does not
   modify any existing technology-specific formats and is defined for
   use in conjunction with new GMPLS Switching Capability types.  The
   context for this document is Generalized MPLS, and the reader is
   expected to be familiar with the GMPLS architecture and associated
   protocol standards.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8258.














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Copyright Notice

   Copyright (c) 2017 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Generalized SCSI Formats  . . . . . . . . . . . . . . . . . .   3
   4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The context for this document is Generalized MPLS, and the reader is
   expected to be familiar with the GMPLS architecture, associated
   terminology, and protocol standards: notably, but not limited to,
   [RFC3945], [RFC4202], [RFC4203] and [RFC5307].

   The Interface Switching Capability Descriptor (ISCD) [RFC4202] allows
   routing protocols such as OSPF and ISIS to carry technology-specific
   information in the Switching Capability-specific information field,
   see [RFC4203] and [RFC5307].  The format of an SCSI field is dictated
   by the specific technology being represented as indicated by the ISCD
   Switching Capability field.  Existing Switching Capabilities are
   managed by IANA in the "Switching Types" registry
   <http://www.iana.org/assignments/gmpls-sig-parameters> and the
   related "IANA-GMPLS-TC-MIB" definitions.






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   [RFC7138] introduced a "sub-TLV" structure to its technology-specific
   SCSI field.  The sub-TLV-based approach allows for greater
   flexibility in the structure, ordering, and ability to support
   extensions of the SC-specific format.  This Sub-TLV approach is also
   used in [RFC7688].

   This document generalizes this approach and defines a new generalized
   SCSI field format for use by future specific technologies and
   Switching Capability types.  The generalized SCSI carries SCSI-TLVs
   that may be defined within the scope of a specific technology or
   shared across multiple technologies (e.g., [AVAIL-EXT]).  This
   document also establishes a registry for SCSI-TLV definitions that
   may be shared across multiple technologies.

2.  Terminology

   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
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The reader is expected to be familiar with GMPLS terminology (e.g.,
   as found in [RFC3945]) as well as the terminology used in [RFC4202],
   [RFC4203], and [RFC5307].

3.  Generalized SCSI Formats

   The Generalized SCSI is composed of zero or more variable-length TLV
   fields each of which is called an "SCSI-TLV".  There are no specific
   size restrictions on these SCSI-TLVs.  Size and other formatting
   restrictions may be imposed by the routing protocol ISCD field (refer
   to [RFC4203] and [RFC5307]).  Please refer to [RFC3630] for the
   treatment of malformed Link TLVs.

   The SCSI-TLV format is:

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |             Type              |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ...                           Value                           ...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 1: TLV Format





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   Type (2 octets):
      This field indicates the type and structure of the information
      contained in the Value field.

   Length (2 octets):
      This field MUST be set to the size, in octets (bytes), of the
      Value field.  The value of the field MUST be zero or divisible by
      4.  Note that this implies that the Value field can be omitted or
      contain padding.

   Value (variable):
      A variable-length field, formatted according to the definition
      indicated by value of the Type field.  This field can be omitted
      for certain types.

4.  Procedures

   The ISCD can include a Generalized SCSI when advertising technologies
   whose Switching Capability definition references this document.  The
   corollary of this is that the Generalized SCSI MUST NOT be used for
   ISCDs of technologies whose Switching Capability definition do not
   reference this document.

   The Generalized SCSI MAY contain a sequence of zero or more SCSI-
   TLVs.  Sub-TLV parsing (format) errors MUST be treated as a malformed
   ISCD.  SCSI-TLVs MUST be processed in the order received and, if re-
   originated, ordering MUST be preserved.  Unknown SCSI-TLVs MUST be
   ignored and transparently processed, i.e., re-originated when
   appropriate.  Processing related to multiple SCSI-TLVs of the same
   type may be further refined based on the definition on the type.

5.  Security Considerations

   This document does not introduce any security issue beyond those
   discussed in [RFC4203] and [RFC5307].  As discussed there, the
   information carried in ISCDs is not used for Shortest Path First
   (SPF) computation or normal routing, and the extensions here defined
   do not have a direct effect on IP routing.  Tampering with GMPLS
   Traffic Engineering (TE) Link State Advertisements (LSAs) may have an
   effect on the underlying transport network.  Mechanisms such as those
   described in [RFC2154] and [RFC5304] to protect the transmission of
   this information are suggested.









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6.  IANA Considerations

   This document defines a new SCSI-TLV that is carried in the SCSI
   field of the ISCDs defined in [RFC4203] and [RFC5307].  The SCSI-TLV
   includes a 16-bit type identifier (the Type field).  The same Type
   field values are applicable to the new SCSI-TLV.

   IANA has created and will maintain a new registry, the "Generalized
   SCSI (Switching Capability Specific Information) TLV Types" registry
   under the "Generalized Multi-Protocol Label Switching (GMPLS)
   Signaling Parameters" registry.

   The initial contents of this registry are as follows:

       Value       SCSI-TLV                Switching Type   Reference
       ---------   ----------------------- --------------   ---------
       0           Reserved                                 [RFC8258]
       1-65535     Unassigned              (value list)


   New allocation requests to this registry must indicate the value or
   values to be used in the Switching Type column.

   The registry should be established with registration policies of
   "Specification Required", see [RFC8126].

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC4202]  Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
              <https://www.rfc-editor.org/info/rfc4202>.







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   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
              <https://www.rfc-editor.org/info/rfc4203>.

   [RFC5307]  Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
              <https://www.rfc-editor.org/info/rfc5307>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2.  Informative References

   [AVAIL-EXT]
              Long, H., Ye, M., Mirsky, G., D'Alessandro, A., and H.
              Shah, "OSPF-TE Link Availability Extension for Links with
              Variable Discrete Bandwidth", Work in Progress,
              draft-ietf-ccamp-ospf-availability-extension-10,
              August 2017.

   [RFC2154]  Murphy, S., Badger, M., and B. Wellington, "OSPF with
              Digital Signatures", RFC 2154, DOI 10.17487/RFC2154, June
              1997, <https://www.rfc-editor.org/info/rfc2154>.

   [RFC3945]  Mannie, E., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Architecture", RFC 3945,
              DOI 10.17487/RFC3945, October 2004,
              <https://www.rfc-editor.org/info/rfc3945>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC7138]  Ceccarelli, D., Ed., Zhang, F., Belotti, S., Rao, R., and
              J. Drake, "Traffic Engineering Extensions to OSPF for
              GMPLS Control of Evolving G.709 Optical Transport
              Networks", RFC 7138, DOI 10.17487/RFC7138, March 2014,
              <https://www.rfc-editor.org/info/rfc7138>.

   [RFC7688]  Lee, Y., Ed. and G. Bernstein, Ed., "GMPLS OSPF
              Enhancement for Signal and Network Element Compatibility
              for Wavelength Switched Optical Networks", RFC 7688,
              DOI 10.17487/RFC7688, November 2015,
              <https://www.rfc-editor.org/info/rfc7688>.




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   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

Acknowledgments

   The authors would like to thank Adrian Farrel and Julien Meuric for
   the careful review and suggestions.  Thomas Heide Clausen provided
   useful comments as part of the Routing Directorate review.

Authors' Addresses

   Daniele Ceccarelli
   Ericsson
   Torshamnsgatan 21
   Kista - Stockholm
   Sweden

   Email: daniele.ceccarelli@ericsson.com


   Lou Berger
   LabN Consulting, L.L.C.

   Email: lberger@labn.net

























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