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Versions: 00 01 draft-ietf-mpls-spl-terminology

MPLS Working Group                                          L. Andersson
Internet-Draft                                  Bronze Dragon Consulting
Updates: 3032, 7274 (if approved)                            K. Kompella
Intended status: Informational                          Juniper Networks
Expires: August 23, 2019                                       A. Farrel
                                                      Old Dog Consulting
                                                       February 19, 2019


                   Special Purpose Label terminology
                draft-andersson-mpls-spl-terminology-00

Abstract

   This document discusses and recommends a terminology that may be used
   when MPLS Special Purpose Labels (SPL) are specified and documented.

   Note: The rest of the text in this section is not really part of the
   abstract even though the text is placed here.  It is working notes.

   Note: At least at the moment it is not the intention to take this
   document to an RFC, but it might be polled to become a wg document to
   see if the MPLS working group agree on the proposed terminology.

   Note: The changes we propose are minor, but we might have to progress
   the document to RFC since there is a proposed change to the "Special-
   Purpose Multiprotocol Label Switching (MPLS) Label Values" registry.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 23, 2019.







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Copyright Notice

   Copyright (c) 2019 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
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   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.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  GMPLS Special Purpose Labels  . . . . . . . . . . . . . .   3
   3.  Terminology and Abbreviations . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   RFC 7274 [RFC7274] made some changes to the terminology used for MPLS
   Special Purpose Labels, but did not define consistent terminology.

   One thing that RFC 7274 did was to deprecate use use of the term
   "reserved labels" when describing a range of labels allocated from a
   registry maintained by IANA.  The term "Reserved" in such a registry
   means "set aside, not to be used", but that range of labels was
   available for allocation according to the policies set out in the
   registry.  The name "Special Purpose Labels" was introduced in RFC
   7274 in place of the previous term, and the abbreviation SPL was
   recommended.

   At the time of posting this Internet-Draft, the IETF is in the
   process of allocating the very first SPLs from the Extended SPL range
   [I-D.ietf-mpls-sfc].  This document discusses and recommends
   terminology and abbreviations to be used when talking about and
   documentating Special Purpose Labels.



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2.  Background

   Two sets of SPLs are defined for use in MPLS:

      The range of SPLs 0-15 is specified in RFC 3032 [RFC3032].

      The range of SPLs 0-1048575 is specified in RFC 7274 [RFC7274].

      *  the values 0-15 has been reserved never to be allocated

      *  the values 15-239 are available for allocation

      *  the values 240-255 are for experimental use

      *  the values 256-1048575 are currently not available for
         allocation, and a standard tracks RFC will be needed to make
         the entire range or part of it available for allocation

2.1.  GMPLS Special Purpose Labels

   Note that IANA maintains a registry called "Special Purpose
   Generalized Label Values".  Labels in that registry have special
   meaning when present in certain signalling objects, are 32 bits long,
   and are not to be confused with MPLS forwarding plane labels.  This
   document does not make any changes to the registry or how labels from
   that registry are described.

3.  Terminology and Abbreviations

   IANA maintains a name space for 'Special-Purpose Multiprotocol Label
   Switching (MPLS) Label Values' code points [SPL-NAME-SPACE].  Within
   this name space there are two registries.  One is called the
   'Special-Purpose MPLS Label Values' registry [rSPL].  The other is
   called 'Extended Special-Purpose MPLS Label Values' registry [eSPL].

   The difference in the name of the name space and the first registry
   is only that the MPLS abbrfeviation is expanded.  This document
   changes the name of the first registry to 'Regular Special-Purpose
   MPLS Label Values', but leaves the name of the latter registry
   unchanged as 'Extended Special-Purpose MPLS Label Values'.

   The following conventions will be used in specifications and when
   talking about SPLs

   o  Collectively, the two ranges are known as Special Purpose Labels
      (SPL).





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   o  The special purpose labels from the lower range will be called
      Regular Special Purpose Labels (rSPL).

   o  The special purpose labels from the higher range will be called
      Extended Special Purpose Labels (eSPL).

   o  The combination of the Extension Label (XL) (value 15 which is an
      rSPL, but that is also called xSPL) and an eSPL is called a
      Composite Special Purpose Label (cSPL).

   This results in a label stacks such as the illustrative examples
   shown in Figure 1 and Figure 2.



             0                                  31
             |     MPLS Label Stack entry        |
             +--------+--------+--------+--------+
             |     MPLS Label Stack entry        |
             +--------+--------+--------+--------+
   rSPL      |            Regular SPL            |
             +--------+--------+--------+--------+
             |  MPLS Label Stack entry (cont.)   |




                     Figure 1: Example of Label Stack



             0                                  31
             |     MPLS Label Stack entry        |
             +--------+--------+--------+--------+
             |     MPLS Label Stack entry        |
             +--------+--------+--------+--------+
   xSPL      |       Extension Label (XL)        | <--+
             +--------+--------+--------+--------+    |--- cSPL
   eSPL      |           Extended SPL            | <--+
             +--------+--------+--------+--------+
             |  MPLS Label Stack entry (cont.)   |




                     Figure 2: Example of Label Stack





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4.  Security Considerations

   This document is entirely about terminology for SPLs and does not
   effect the forwarding in the MPLS data plane, nor does it have any
   effect on how LSPs are establsihed by an MPLS control plane or by a
   centralized controller.  The doucment describes a terminology to be
   used when describing and specifying the use of SPLs.

   This document does not aim to describe existing implementations of
   SPLs or the potential vulnerabilities of SPLs.

5.  IANA Considerations

   We request that the name of the IANA registry that today is called
   "Special-Purpose MPLS Label Values" is changed to "Regular Special-
   Purpose MPLS Label Values".

6.  Acknowledgements

   -

   -

7.  References

7.1.  Normative References

   [eSPL]     "Extended Special-Purpose MPLS Label Values",
              <https://www.iana.org/assignments/mpls-label-values/
              mpls-label-values.xhtml#extended/>.

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <https://www.rfc-editor.org/info/rfc3032>.

   [RFC7274]  Kompella, K., Andersson, L., and A. Farrel, "Allocating
              and Retiring Special-Purpose MPLS Labels", RFC 7274,
              DOI 10.17487/RFC7274, June 2014,
              <https://www.rfc-editor.org/info/rfc7274>.

   [rSPL]     "Special-Purpose MPLS Label Values",
              <https://www.iana.org/assignments/mpls-label-values/
              mpls-label-values.xhtml#special-purpose/>.







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   [SPL-NAME-SPACE]
              "Special-Purpose Multiprotocol Label Switching (MPLS)
              Label Values", <https://www.iana.org/assignments/
              mpls-label-values/mpls-label-values.xhtml/>.

7.2.  Informative References

   [I-D.ietf-mpls-sfc]
              Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
              Forwarding Plane for Service Function Chaining", draft-
              ietf-mpls-sfc-05 (work in progress), February 2019.

Authors' Addresses

   Loa Andersson
   Bronze Dragon Consulting

   Email: loa@pi.nu


   Kireeti Kompella
   Juniper Networks

   Email: kireeti@juniper.net


   Adrian Farrel
   Old Dog Consulting

   Email: adrian@olddog.co.uk





















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