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

Philip Homburg <pch-v6ops-9@u-1.phicoh.com> Tue, 16 February 2021 15:20 UTC

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To: v6ops@ietf.org
Cc: Fernando Gont <fgont@si6networks.com>, "6man@ietf.org" <6man@ietf.org>
Subject: Re: [v6ops] [EXTERNAL] Re: Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)
From: Philip Homburg <pch-v6ops-9@u-1.phicoh.com>
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In-reply-to: Your message of "Tue, 16 Feb 2021 12:09:42 -0300 ." <6959c883-a255-5ab8-9027-e05d369af2ff@si6networks.com>
Date: Tue, 16 Feb 2021 16:20:14 +0100
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>> Python apparently wrongly identifies a ULA as non-global. Reading the 
>> ULA specification would have helped with that. 
>
>But reading the "ipv6 scoped addressing architecture" (RFC4007) would 
>have suggested that what they did is correct.

In my opinion, ULA is sufficiently different from rfc1918 that mapping them
to the same concept in a programming language will only lead to issues
that are hard to resolve.

In today's internet, an RFC 1918 address is likely behind NAT. So you can
use the address as source address to communicate with the wider IPv4 internet.
You may need to use NAT traversal tools. It is very unlikely that there will
be another IPv4 address available.

With ULA, using the ULA as source address is not going to connect you the
wider IPv6 internet. NAT is unlikely. But there is a good chance that there
is another IPv6 address that can reach the rest of the internet.

In other words, though both RFC 1918 and ULA have some sort of 'local' aspect,
they differ in just about every other aspect.