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

Brian E Carpenter <> Fri, 19 February 2021 00:36 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 939903A0839; Thu, 18 Feb 2021 16:36:49 -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 CBXpIQyd491E; Thu, 18 Feb 2021 16:36:47 -0800 (PST)
Received: from ( [IPv6:2607:f8b0:4864:20::432]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id AA3643A0801; Thu, 18 Feb 2021 16:36:34 -0800 (PST)
Received: by with SMTP id k13so2665301pfh.13; Thu, 18 Feb 2021 16:36:34 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=subject:to:cc:references:from:organization:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=c8z4XM5ptou+bh9uSBIA1KOeZL/9fcdM1b1epJJynvg=; b=PHmf4SDvvkhsOS3VDQdreFaKKiLtiYvLhPOmgbvV7bgUATTa4s7zUl6/cpHBJurDvj Aei8odxV4/pS7E9l+y6XeUm+rh6sV0+G9iAg9vyUBhIClhGj/GlQWvhwUy/eF6qNXwhy +8T1Qs4S9NdROT4M3ItfeMzL9y7Wvt1gJwz2vKFaw+sYlFfjjh1tuHK5nvObL6FmiIBc xhFaR6o2xqj5kJK9q65udCbdo6ZRYww87uIdHP0FvR/1Sd2AYgmaXB4evRjsOJ11axCF GxuV4VZaYC5KW2XhQetWbqbSxaMdTnhm/sjKUUuG1iprT7uw3Ekl8jMPxpmeooKCsDxU I+kQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=c8z4XM5ptou+bh9uSBIA1KOeZL/9fcdM1b1epJJynvg=; b=AvCZM2T3Cfe1AKpiQXd2MaUitLqjKpwar2gG+jHgsymvG4tmydkzQBsBb+/bTxJ4fi erJ5Wwkhkj0RkMmWYe9IkZyU9jHnVIGMf+JgbwsWKbSoTxEfowsRotGV0IbLV54xqUqZ 80G3xO4G85aHPBKIN31KAsgXGluRVAqYdD9we0HSfML7u5KAnkAS4ooSgquFIHxQobuD AKrxV6Joom3k/+W8tBtcjyBRV4j5BNk+xq9RROQ9uVBJbu+jeYdx2MxSmmKVt0htmJbw kUMrve6tYrAm4GlBLY7yrLb7E/ebgdfyfGbHU9mUZv1wvYl1rN6tQUXY6uFuQopIw0JU RxKA==
X-Gm-Message-State: AOAM530/38RB29dc+Za1psnTLg5D/awLhG+jjmKKPLIng8E3DYt6lsfX 7jWqip1Yq5COBjQtcpSz0bwbk9b8z1Gl7Q==
X-Google-Smtp-Source: ABdhPJx9QNQ4JCB2Lyw85siv8usXrMY7gckG/1e6lMGh31J0TqR2rrpDk5tVR1rwALTSr8prqU4Ywg==
X-Received: by 2002:a63:154e:: with SMTP id 14mr6246548pgv.18.1613694993534; Thu, 18 Feb 2021 16:36:33 -0800 (PST)
Received: from [] ([]) by with ESMTPSA id w187sm7239392pgb.52.2021. (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Feb 2021 16:36:33 -0800 (PST)
To: Fernando Gont <>, "Manfredi (US), Albert E" <>
Cc: IPv6 Operations <>, "" <>
References: <> <> <> <> <>
From: Brian E Carpenter <>
Organization: University of Auckland
Message-ID: <>
Date: Fri, 19 Feb 2021 13:36:28 +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: 7bit
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: Fri, 19 Feb 2021 00:36:50 -0000

So, my thought (and it belongs on this thread OR the 'IPv6 addressing: Gaps?' one) is something like:

We should abolish, delete, expunge and deprecate the word "scope" from all IPv6 documents. It clearly doesn't have an agreed meaning, so it is worse than useless.

All addresses have a region of reachability. This may be confined to a single "link" (whatever a "link" means), some type of limited domain (such as, but not limited to, a "site" (whatever a "site" means)), or to a large part of the Internet as a whole (knowing that there is in reality no such thing as "the" Internet.)

LL addresses MUST NOT be used off a given L2 link.
ULAs MUST NOT be routed outside a given limited domain.
GUAs MAY be routed anywhere.

(MANETs and other mesh networks don't fit in there very well.)


On 19-Feb-21 12:58, Fernando Gont wrote:
> On 18/2/21 20:39, Manfredi (US), Albert E wrote:
>> -----Original Message-----
>> From: ipv6 <> On Behalf Of Fernando Gont
>>> Well, this is a spec inconsistency. You have one spec (RFC4007) defining
>> "scope" and "global scope", and another specs:
>>> a) making use of the same terms in an incorrect way, or,
>>> b) employing same terms but with a different definition.
>>> i.e., either the definition in RFC4007 is incorrect, or the use in
>> RFC4193 and implicit use in RFC4291 is incorrect.
>> You can also argue, if there are prefix bits sent in the clear, and those prefix bits are used to send the packets to a pre-determined gateway, and that gateway is then used to decrypt all of the remaining address bits, then route packets through a walled garden intranet with global span, then global scope could still apply.
> "global span" is defined as "Internet-wide" span. i.e., if an address 
> does not unambiguously specify an interface Internet-wide, it's not 
> global scope as per RFC4007.
>> Just sayin'. These still aren't like RFC 1918.
> The only practical differences I see with respect to rfc1918 are:
> 1) ULAs are not intended to be used with NAT.
> However, were RFC1918 strictly specified to be employed along with NAT? 
> Besides "not indended" != "won't be".
> 2) ULAs are intended to have a small probability of collision when a 
> subset of ULA-based networks are interconnected.
> This is the product of mandating that some bits are generated from a 
> PRNG, plus the fact that ULAs have more bits than their RFC1918 counterpart.
> If I have missed any other differences, please enlighten me. :-)
> Thanks,