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

Fernando Gont <> Sun, 14 February 2021 21:54 UTC

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To: Ted Lemon <>, David Farmer <>
Cc: Brian E Carpenter <>, IPv6 Operations <>, "" <>
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From: Fernando Gont <>
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Date: Sun, 14 Feb 2021 18:52:56 -0300
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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)
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On 14/2/21 18:32, Ted Lemon wrote:
> My question to you is this: how does your proposed update help anybody 
> to understand?
> If we were to update the text, I would suggest something like this:
> Global scope, for uniquely identifying interfaces anywhere on the 
> Internet. Note that when we say an address is “globally unique,” this is 
> a definitional assertion: such an address is to be treated as globally 
> unique by hosts and routers. Mechanisms for ensuring that this 
> definitional assertion is not violated exist for each type of globally 
> scoped address, and in some cases rather than ensuring that a globally 
> /scoped/ address is in fact unique, these mechanisms ensure that the use 
> of such addresses is constrained to contexts in which they are /known/ 
> to be unique.

If the definition of scope is that of RFC4007:

       "[the] topological span within which the address may be used as a
       unique identifier for an interface or set of interfaces

ULAs can't be global.

So, either ULAs (and others) are not global, or scope means something 
different than what's in RFC4007.

i.e. the key is in the definition of "scope".

Since I find the definition of scope in RFC4007 quite succint and clear, 
my take is/was that the easier and simpler fix is that ULAs are not global.

Fernando Gont
SI6 Networks
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