Re: [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> Thu, 07 January 2021 21:36 UTC

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Subject: Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)
To: David Farmer <farmer@umn.edu>
Cc: Brian E Carpenter <brian.e.carpenter@gmail.com>, Lorenzo Colitti <lorenzo=40google.com@dmarc.ietf.org>, Mark Smith <markzzzsmith@gmail.com>, IPv6 Operations <v6ops@ietf.org>, 6MAN <6man@ietf.org>
References: <160989494094.6024.7402128068704112703@ietfa.amsl.com> <6fe3a45e-de65-9f88-808d-ea7e2abdcd16@si6networks.com> <CAO42Z2wR-3vbHi-NrBBMmCTNDq5fgqvSmBUbYK7P+63QTNfxkg@mail.gmail.com> <CAKD1Yr014PzVJj9Y6O=PBGc_QSVtur-0wMpaNkFA0dqr8FHGuA@mail.gmail.com> <44e7ac61-523a-d35e-9024-7e6df81e4226@gmail.com> <be92f523-eeaa-8ed4-afdf-4a537f53748c@si6networks.com> <CAN-Dau2S9pXYAwrRbfT9aMyXPw-NYaOxKF+nXRg_14zqTr8F0g@mail.gmail.com>
From: Fernando Gont <fgont@si6networks.com>
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Date: Thu, 7 Jan 2021 18:35:28 -0300
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On 7/1/21 08:08, David Farmer wrote:
> Sorry for the top post.
> 
> Fernando, you are correct that by the definition of global scope in 
> RFC4007, ULA is not global scope.
> 
> However, Brian and RFC4139 are also correct, given the intended 
> reachability domain for ULA, it has a uniqueness that is many many 
> orders of magnitude greater than is necessary for the task. So, while 
> not technically global scope as defined in RFC4007 it is effectively 
> global scope in any way that matters.

BUt this is like a circular definition. Because it's kind of saying 
something like "ULAs are globally unique as long as the have local scope".

In order for them to have "global scope", they need to be globally 
unique. And you note that "they are essentially unique, gven an 
appropriate scope".




> I have an idea for what to call ULA's scope without redefining global 
> scope in RFC4007, how about we call ULA's scope "pseudo-global" scope.
> 
> This gives us;
> 
> Link-Local > Site-Local >>>>>> Pseudo-Global > Global

I don't think the site-local scope, in terms of network span, is 
necessarily larger than that of ULAs.



> Calling ULA pseudo-global scope I believe conveys RFC4139's 
> original intent without conflicting with the definition of global scope 
> in RFC4007, while still allowing it to be treated effectively as if it 
> is global scope.
> 
> What do other people think?

IMO, that'd keep the confusion. At the end of the day, if your nor going 
to call them "global scope", the specific name for the scope doesn't 
really matter... as long as it is properly defined, and used consistently.

-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492