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

Fernando Gont <> Thu, 07 January 2021 21:36 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 6AEBE3A00C9; Thu, 7 Jan 2021 13:36:07 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.161
X-Spam-Status: No, score=-2.161 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, NICE_REPLY_A=-0.262, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id Uub-ntZFgPcf; Thu, 7 Jan 2021 13:36:03 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 8DC943A0062; Thu, 7 Jan 2021 13:36:01 -0800 (PST)
Received: from [] (unknown []) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPSA id 7CEDA2845B1; Thu, 7 Jan 2021 21:35:53 +0000 (UTC)
To: David Farmer <>
Cc: Brian E Carpenter <>, Lorenzo Colitti <>, Mark Smith <>, IPv6 Operations <>, 6MAN <>
References: <> <> <> <> <> <> <>
From: Fernando Gont <>
Message-ID: <>
Date: Thu, 7 Jan 2021 18:35:28 -0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Archived-At: <>
Subject: Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: v6ops discussion list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 07 Jan 2021 21:36:08 -0000

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
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492