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

Fernando Gont <fgont@si6networks.com> Fri, 19 February 2021 03:22 UTC

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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)
To: Mark Smith <markzzzsmith@gmail.com>, Brian E Carpenter <brian.e.carpenter@gmail.com>
Cc: "Manfredi (US), Albert E" <albert.e.manfredi@boeing.com>, IPv6 Operations <v6ops@ietf.org>, "6man@ietf.org" <6man@ietf.org>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Fri, 19 Feb 2021 00:06:42 -0300
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On 18/2/21 22:21, Mark Smith wrote:
> 
> 
> On Fri, 19 Feb 2021, 11:37 Brian E Carpenter, 
> <brian.e.carpenter@gmail.com <mailto:brian.e.carpenter@gmail.com>> wrote:
> 
>     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.
> 
> 
> I think the word scope is fine.
> 
> The problem is that by itself it doesn't specify what thing the scope is 
> applying to, and people aren't explicitly saying what that scope they're 
> referring to. "Global scope" - scope of what?

As per RFC4007, scope refers to address uniqueness.



> ULAs (and addresses in general) have at least two different scopes:
> 
> - scope or domain of intended uniqueness

For ULAs, this is "set of interconnected ULA-based networks" -- i.e., 
some sort of limited domain/scope.



> - scope or domain of intended forwarding within a network or across a 
> set of networks

In this case, same as before.

Normally, both of these are equal: and address uniqueness will limit 
reachability.



> "Scope" and "domain" seem to almost be synonyms. "Global domain", 
> without specifying what "domain" refers to, would have the same problems 
> as the term "global scope".

Per RFC4007, it's global uniqueness it refers to.

That's why https://www.rfc-editor.org/rfc/rfc8190.txt introduced the 
flag "globally reachable" to the "IANA IPv6 Special-Purpose Address 
Registry".

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492