Re: Non routable IPv6 registry proposal

Brian E Carpenter <> Fri, 12 March 2021 01:39 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id C5BC83A17B7 for <>; Thu, 11 Mar 2021 17:39:29 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.099
X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, NICE_REPLY_A=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id IGxI8Rpo5zg0 for <>; Thu, 11 Mar 2021 17:39:27 -0800 (PST)
Received: from ( [IPv6:2607:f8b0:4864:20::635]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id D93933A17B9 for <>; Thu, 11 Mar 2021 17:39:27 -0800 (PST)
Received: by with SMTP id q12so684478plr.1 for <>; Thu, 11 Mar 2021 17:39:27 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=aazHUKWtBa7aUdX1UkG86aboLgsTHBHC9tBrXSVyJyw=; b=tGxL2+RtzqNYQtyhyneFupUwPIK7c5V2x8YKAoF8usq2aR8KUQ1gIEpI0KMhBQxl05 KVC5HoyOSFvAlQlh5YOGcdA342kMv+c5JPzHvDgIs2EwPKpNsQWnqdY9cju5KCKJhynq 8s9e3Xh3egTZP5es+KHOrOGsCqKC2JaZEceBdqs0+4nfQUSft1vswiePbkmxspelfdZp 6sgqj5HP0HDcDJ2fDRgyP2mIqKplGkv/Z1Ru+Et+mfed0Y2OWmgvg8f8KKaKlfS++Dp7 E2JZukd+Ayvi2EQh2LsqIEYCcayfPzN7N+3yuRe0lu3nmv1dP7FhuhwfmJAH6qfdXWh8 iOZQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=aazHUKWtBa7aUdX1UkG86aboLgsTHBHC9tBrXSVyJyw=; b=ku1IXJRdRdsN/0KHq1TZEGZtUf8251WIev9OvcRTqn08dEON0D2vEZwZcnnuRETlit QNJzH4w8hPsnltwHyV0cVo/H8HWZY4eRBY071T4yuRJvp8CzYdSVuajTz2DbR5f+YFVA 2+GgUB7WVdbwVjKkOYSjSMuLnzTg8uaPzQGlpprxfsYWOx7ic88+HFi11W2uviBbWxI1 EvyqT7ygdqoL3eqon0hpI9O5Hjg/4xx3aH2uW2LL4jNXOPYu+Td7sblLqYdaQhuMdc4c EKM0yYD9MPddypXei/vdC7HTujtzRzxH104sSYAC63gusWhPA4pmS1hKtI+cazSIghAe FYUA==
X-Gm-Message-State: AOAM531RV+hN9G2aiToGRPtN/jQX9aoBaBPs6OkYQlNY1Ibfh4tJJkm6 /bXg2QQiGgsmin/g8e92W5o=
X-Google-Smtp-Source: ABdhPJzch9FTO1Bm/nQa7jG6bb2N5N5LUT2fNAnuvNwGbLHcX3O6qoIiAZ1O1x3HM81Z/HDXL9c1aQ==
X-Received: by 2002:a17:90a:fa89:: with SMTP id cu9mr11936459pjb.204.1615513166443; Thu, 11 Mar 2021 17:39:26 -0800 (PST)
Received: from [] ([]) by with ESMTPSA id g18sm3639520pfb.178.2021. (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Mar 2021 17:39:25 -0800 (PST)
Subject: Re: Non routable IPv6 registry proposal
To: David Farmer <>
Cc: Keith Moore <>, IETF-Discussion Discussion <>, Nico Schottelius <>
References: <> <> <> <> <> <> <> <> <> <> <>
From: Brian E Carpenter <>
Message-ID: <>
Date: Fri, 12 Mar 2021 14:39:20 +1300
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: quoted-printable
Archived-At: <>
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: IETF-Discussion <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 12 Mar 2021 01:39:30 -0000

On 12-Mar-21 09:51, David Farmer wrote:
> On Thu, Mar 11, 2021 at 2:16 PM Brian E Carpenter < <>> wrote:
>     David,
>     On 12-Mar-21 08:19, David Farmer wrote:
>     > On Thu, Mar 11, 2021 at 10:49 AM Keith Moore < <> < <>>> wrote:
>     >
>     >     On 3/11/21 5:22 AM, Nico Schottelius wrote:
>     >
>     >>>     Another question I have is whether such ULA allocations
>     >>>     will realistically remain local.
>     >>     ULAs are unlikely staying local, as we have seen with radio networks in
>     >>     Germany. Tunnels are being used to interconnect remote cities and
>     >>     non-collision (not necessarily public routing) are a primary concern.
>     >
>     >     Despite the name, there's no reason that ULAs should stay local.   As long as they are properly chosen, it's perfectly reasonable to route them privately between cooperating networks, and IMO this is part of their design.   One of the problems with RFC 1918 addresses in IPv4 was that enterprises had a need to route traffic between networks each using that space.   The resulting address collisions generally required explicit NAT configurations to work around, and these were failure-prone and difficult to manage.  ULAs were intended in part to remedy this problem.
>     >
>     >     Keith
>     >
>     > The "L" for Local isn't intended to have a strict definition of Local. However, similarly, the "U" for Unique isn't intended to have a strict definition of Unique either, especially a mathematical definition of Unique. 
>     >
>     > You can easily interconnect thousands or even tens of thousands of ULA prefixes without much chance of an address collision, as long as the random assignment process is actually used. Whereas, if you try to interconnect billions of ULA prefixes, you will probably start running into the birthday paradox.
>     >
>     > So the interconnection of ULA prefixes, the route-ability of them, is not intended to be unlimited. There are limits to the number of ULA prefixes that SHOULD be interconnected to each other; nevertheless, this limit is extremely generous for the intended use cases.
>     >
>     > If you disregard the intended use cases and use them outside the intended use cases, then address collisions could become an issue.
>     I'm not sure where you get your "intended" from. I don't think we've ever really written done the intended use cases in such detail. (Except for the abandoned )
>         Brian
> The first sentence of the Abstract for RFC4193 says;
>     This document defines an IPv6 unicast address format that is globally unique and is intended for local communications, usually inside of a site.
> This is expanded upon in the first paragraph of the Introduction to RFC4193;
>     This document defines an IPv6 unicast address format that is globally unique and is intended for local communications [IPV6]. ...
>     They are routable inside of a more limited area such as a site.  They may also be routed between a limited set of sites.
> Those sound a lot like intended use cases to me, the key phrases in that for me are, "local communications", "usually ... a site", and "a limited set of sites." 
> Yes, that's pretty vague, but I don't see a reasonable interpretation of those phrases that include every site on the Internet, or even every site in a country or state, maybe it could include every site in a small to modest city, but even that's a bit of a stretch in my opinion.

Yes, agreed, but somehow your previous message made me think you meant more than that.

Nico's use case seems a bit different though. He seems to be saying that there's a "ham radio" or "CB radio" type of use case where arbitrary sets of users anywhere in the world might want to route between themselves without paying any ISP for the privilege, so they'd like free address space too. Quite how they'd get the bandwidth without paying for it is a puzzle though. Generally that's the main cost element in ISP pricing.

Nico, a full length description of the use case as an Internet-Draft would be very helpful. We could take that to v6ops for discussion.