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

Philip Homburg <pch-v6ops-10@u-1.phicoh.com> Mon, 15 February 2021 15:12 UTC

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In-reply-to: Your message of "Fri, 12 Feb 2021 17:55:17 -0800 ." <9877D352-E9BB-453B-A676-D2B5C546C1C2@gmail.com>
Date: Mon, 15 Feb 2021 16:11:55 +0100
Archived-At: <https://mailarchive.ietf.org/arch/msg/v6ops/NRYCsSdwCEg_qqqCOPGKjM-xqYY>
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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>No. Global scope, per the RFC  you're quoting, is "Global scope, for
>uniquely identifying interfaces anywhere in the Internet."

I think it is time to revisit this definition.

Anycast is widely used on the internet. In some deployments, a single anycast
address is announced from multiple ASes.

A bit earlier in RFC 4007 we have 'scope; that is, a topological span within
which the address may be used as a unique identifier for an interface or
set of interfaces.'

What does that even mean? From a maths point of view, if we have two sites
that use the same ULA, then the ULA address is a unique identifer for a set of
interfaces. How does that help?

In the case of anycast, a GUA may refer to a set of interfaces, but that
set does not need to be stable (as112 for example) 

Effectively the only thing we know about global addresses is that they
are not link local (and not multicast or unspecified)