Allocating and Retiring MPLS Reserved Labels
draft-kompella-mpls-special-purpose-labels-01

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Document Type Active Internet-Draft (mpls WG)
Last updated 2013-03-14 (latest revision 2012-10-15)
Replaces draft-kompella-mpls-reserved-labels
Replaced by draft-ietf-mpls-special-purpose-labels, rfc7274
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Network Working Group                                        K. Kompella
Internet-Draft                                          Contrail Systems
Updates: 3032 (if approved)                                 L. Andersson
Intended status: Standards Track                                Ericsson
Expires: April 18, 2013                                        A. Farrel
                                                        Juniper Networks
                                                        October 15, 2012

              Allocating and Retiring MPLS Reserved Labels
             draft-kompella-mpls-special-purpose-labels-01

Abstract

   Some MPLS labels have been allocated for specific purposes.  A block
   of labels (0-15) has been set aside to this end, and are commonly
   called "reserved labels".  They will be called "special purpose
   labels" in this document.  As there are only 16 of these labels,
   caution is needed in the allocation of new special purpose labels,
   yet at the same time allow forward progress when one is called for.
   This memo defines some procedures to follow in the allocation and
   retirement of special purpose labels, as well as a method to extend
   the special purpose label space.  Finally, this memo renames the IANA
   registry for these labels to "Special Purpose MPLS Label Values", and
   creates a new one called the "Extended Special Purpose 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
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   This Internet-Draft will expire on April 18, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Internet-Draft            MPLS Reserved Labels              October 2012

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions used . . . . . . . . . . . . . . . . . . . . .  3
   2.  Questions  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Answers  . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Extended Special Purpose MPLS Label Values . . . . . . . .  5
     3.2.  Process for Retiring Special Purpose Labels  . . . . . . .  6
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     6.2.  Informational References . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

Kompella, et al.         Expires April 18, 2013                 [Page 2]
Internet-Draft            MPLS Reserved Labels              October 2012

1.  Introduction

   The specification of the Label Stack Encoding for Multi-Protocol
   Label Switching (MPLS) [RFC3032] defined four special purpose label
   values (0 to 3), and set aside values 4 through 15 for future use.
   These labels have special significance in both the control and the
   data plane.  Since then, three further values have been allocated
   (values 7, 13, and 14 in [I-D.ietf-mpls-entropy-label], [RFC5586] and
   [RFC3429], respectively), leaving nine unassigned values from the
   original space of sixteen.

   While the allocation of three out of the remaining twelve special
   purpose label values in the space of about 12 years is not in itself
   a cause for concern, the scarcity of special purpose labels is.
   Furthermore, many of the special purpose labels require special
   processing by forwarding hardware, changes to which are often
   expensive, and sometimes impossible.  Thus, documenting a newly
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