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> Sat, 13 February 2021 20:19 UTC

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To: Brian E Carpenter <brian.e.carpenter@gmail.com>, Ted Lemon <mellon@fugue.com>, Fred Baker <fredbaker.ietf@gmail.com>
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From: Fernando Gont <fgont@si6networks.com>
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Date: Sat, 13 Feb 2021 17:18:40 -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 13/2/21 17:03, Brian E Carpenter wrote:
> On 13-Feb-21 16:17, Fernando Gont wrote:
>> On 13/2/21 00:08, Brian E Carpenter wrote:
>>> OK, I have deleted all the content (but basically I agree with Ted
>>> Lemon). IMHO:
>>>
>>> ULAs SHOULD be treated exactly like GUAs for all practical purposes
>>> (including using a default router for them), with the exception that
>>> they MUST be filtered by border routers at a domain boundary that is
>>> defined administratively. The only extra requirement is that ULA
>>> prefixes MUST be unique within that domain boundary. That's all, I
>>> think.
>>
>> FWIW, in the context of draft-ietf-6man-slaac-renum, it has been argued
>> that: "only phase out GUAs if you hear of new GUAs, and only phase out
>> ULAs if you hear of new ULAs" -- i.e., that they should be treated
>> differently.
>>
>> (Note: I'm not necessarily arguing in favor of this.)
> 
> I think it makes sense, since the basic scenario is to have one ULA
> for local communication and one GUA for Internet-wide communication.
> Having more than one ULA prefix on a link is rather unnatural.

BUt that's again ULAs being special. And they usually have properties of 
"private" addresses -- e.g., can generally be expected to be valid if 
your link to your ISP goes down, are more unlikely of being renumbered, etc.



>>> As for the word "scope" and the phrase "global scope" it may be best
>>> to not use them at all. We originally had a false notion of
>>> concentric rings of address scope, but reality is a very complex Venn
>>> diagram. Even link-local may stop being very meaningful as we see
>>> more and more mesh networks. That will be much harder to handle than
>>> any aspect of ULAs.
>>
>> Deprecate/rev RFC4007? :-)
> 
> I think we'd have a lot of documents to touch if we wanted to resolve
> this rather than just live with it

On a quick though, it would seem to me the necessary documents are 
RFC4291, RFC4007, and RFC4193.

-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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