Scope of Unique Local IPv6 Unicast Addresses
draft-gont-6man-ipv6-ula-scope-00

Document Type Active Internet-Draft (individual)
Author Fernando Gont 
Last updated 2021-01-05
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IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                              SI6 Networks
Updates: 4291, 4193, 8190 (if approved)                  January 5, 2021
Intended status: Standards Track
Expires: July 9, 2021

              Scope of Unique Local IPv6 Unicast Addresses
                   draft-gont-6man-ipv6-ula-scope-00

Abstract

   Unique Local IPv6 Unicast Addresses (ULAs) are formally part of the
   IPv6 Global Unicast address space.  However, the semantics of ULAs
   clearly contradict the definition of "global scope".  This document
   discusses the why the terminology employed for the specification of
   ULAs is problematic, along with some practical consequences of the
   current specification of ULAs.  Finally, it formally updates RFC4291
   and RFC4193 such that the scope of ULAs is defined as "local".

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on July 9, 2021.

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   Copyright (c) 2021 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
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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.  What Does 'Global Scope' mean?  . . . . . . . . . . . . . . .   2
   3.  Scope of Unique Local IPv6 Unicast Addresses  . . . . . . . .   3
   4.  Problems with the Definition of the ULA Scope . . . . . . . .   4
   5.  Practical Consequences  . . . . . . . . . . . . . . . . . . .   4
     5.1.  Address Attributes in Programming Languages . . . . . . .   5
   6.  Specification Updates . . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Unique Local IPv6 Unicast Addresses (commonly referred to as "ULAs")
   [RFC4193] are formally part of the IPv6 Global Unicast address space.
   However, the semantics of ULAs clearly contradict the definition of
   "global scope" [RFC4007].

   This document discussed the specification of ULAs and, in particular,
   of their associated scope.  Additionally, it discusses how the
   semantics of ULAs contradicts their formal address scope along with
   some and practical consequences of this problematic definition.
   Finally, this document formally updates RFC4193 and RFC4291, such
   that ULAs are defined to have "local scope" (larger than link-local,
   and smaller than "global").

      The problematic definition of ULAs was initially encountered when
      analyzing IPv6 address properties while working on
      [I-D.gont-v6ops-ipv6-addressing-considerations].  The issue became
      fully-evident from discussions with Brian Carpenter, both off-list
      and on-list [v6ops-thread].

2.  What Does 'Global Scope' mean?

   [RFC4007] defines the scope of an address as:

      "[the] topological span within which the address may be used as a
      unique identifier for an interface or set of interfaces"

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   And defines the "global scope" to be used for:

      "uniquely identifying interfaces anywhere in the Internet"
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