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

Fernando Gont <> Sat, 13 February 2021 21:53 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 6DA083A11C3; Sat, 13 Feb 2021 13:53:52 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, NICE_REPLY_A=-0.001, 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 QBigZhu4MFz3; Sat, 13 Feb 2021 13:53:50 -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 7D83C3A11BB; Sat, 13 Feb 2021 13:53:37 -0800 (PST)
Received: from [IPv6:2800:810:464:2b9:1c77:acfc:e6a8:1311] (unknown [IPv6:2800:810:464:2b9:1c77:acfc:e6a8:1311]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPSA id 0FB38280204; Sat, 13 Feb 2021 21:53:32 +0000 (UTC)
From: Fernando Gont <>
To: Brian E Carpenter <>, David Farmer <>, Fred Baker <>
Cc: IPv6 Operations <>, "" <>
References: <> <> <> <> <> <> <>
Message-ID: <>
Date: Sat, 13 Feb 2021 18:53:25 -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: Sat, 13 Feb 2021 21:53:59 -0000

On 13/2/21 18:33, Fernando Gont wrote:
> On 13/2/21 18:17, Brian E Carpenter wrote:
>> On 13-Feb-21 22:19, Fernando Gont wrote:
>> ...
>>> Well, whether we call it out or not, as per RFC4007:
>>>                 scope(LL) < scope(ULA) < scope(GUA)
>> And there's the fallacy. This inequality only makes sense if 
>> reachability is strictly a matter of concentric circles. It isn't. 
>> Nice math, but not reality.
>> Slide 4 of
> I don't follow. In all of your slides Area(link-local) < Area(ULA) < 
> Area(global)....

I assume that the "site" refers to the (deprecated) "site-local" 
addresses, and what you try to point out in slide #4  is that it's at 
odda with RFC4007, which specifies there can only be one zone for each 

However, I consider *that* requirement rather flawed.

Slide #4 could indeed be the case where a node attaches to a subnet 
where .e.g two different routers advertise different ULA prefixes -- and 
one or the two of them also advertises global prefixes.

Each shaded "site" constitutes a different layer (as in John Day's PNA).
In principle, hosts on each of the shaded sites cannot reach hosts on 
the other shaded site (since they are in different layers).

But all can communicate via the global layer.

Not sure what'd be the problem with that...

Fernando Gont
SI6 Networks
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492