[v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)

Fernando Gont <fgont@si6networks.com> Wed, 06 January 2021 01:21 UTC

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Subject: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)
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Based on the recent discussion on the v6ops list 
I've posted this new I-D, meant to discuss the scope of ULAs:

Title: "Scope of Unique Local IPv6 Unicast Addresses"
I-D: https://tools.ietf.org/id/draft-gont-6man-ipv6-ula-scope-00.txt

Short version of the story:

ULAs are formally part of the GUA space. However, the characteristics of 
ULAs do not seem to match the definition of global scope from RFC4007 
(IPv6 Scope Addr Architecture). ULA seem to have a scope of 
scope(link-local) < scope(ULA) < scope(GUA).

This is not only a terminology thing (which I think is nevertheless 
important to get right) but also has practical implications. For 
example, there's a python library that considers ULAs as "not global", 
and "private" -- contradicting the current RFC4291/RFC4193 specs.

Prior to posting this document, we had some on-list discussion (on the 
v6ops list) and also some off-list discussion with some of you (bcc'ed).

The opinions have been in one of these camps:

1) the current specs are coherent and there's no problem

2) There's a problem with the definition of "global scope" -- so ULAs 
*are* global scope, but global scope does not really stand for the 
definition in RFC4007.

3) The definitions in RFC4007 are correct, and thus the scope of ULAs is 
not really global, but scopee(link-local) < scope(ULAs) < scope(global)

While this document does propose a way out (it assumes #3 above, and 
acts accordingly), I believe the first step is to agree on what "global 
scope" means and, subsequently, whether ULAs are really "global scope" 
or not. Since opinions on the topic have vary a lot (as noted above), 
I've posted this I-D and I'm sending this note for further input from 
the WG.



-------- Forwarded Message --------
Subject: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt
Date: Tue, 05 Jan 2021 17:02:20 -0800
From: internet-drafts@ietf.org
To: Fernando Gont <fgont@si6networks.com>

A new version of I-D, draft-gont-6man-ipv6-ula-scope-00.txt
has been successfully submitted by Fernando Gont and posted to the
IETF repository.

Name:		draft-gont-6man-ipv6-ula-scope
Revision:	00
Title:		Scope of Unique Local IPv6 Unicast Addresses
Document date:	2021-01-05
Group:		Individual Submission
Pages:		8

    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".


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