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 21:12 UTC

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To: Ted Lemon <mellon@fugue.com>
Cc: David Farmer <farmer@umn.edu>, Fred Baker <fredbaker.ietf@gmail.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: Sat, 13 Feb 2021 18:11:47 -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 17:45, Ted Lemon wrote:
> On Feb 13, 2021, at 3:15 PM, Fernando Gont <fgont@si6networks.com 
> <mailto:fgont@si6networks.com>> wrote:
>> Well, other addresses also share the same property -- they are valid, 
>> but they identify a different thing -- an interface in a different 
>> subnet.  e.g., address fe80::1 is valid on avery single network 
>> segment -- but the issue is that, en each of them, it most likely 
>> identifies a different thing. -- and that comes from the uniqueness 
>> property.
> 
> Yes, but a local address is never valid to forward, by definition. 
> That’s what I mean by “by definition.”

Then the definition of scope would become related with what you can or 
cannot do with the address, which seems much more cumbersome that the 
clear definition of scope that we currently have in RFC4007.

And if you want to get into that, then you'd have tricky cases such as a 
host using fe80::1 on two different interfaces and implementing the weak 
end-host mode (RFC1122). Say you have a socket bound to only one address 
on one interface, and receive a packet for that (address, port) but *on 
the other interface*:  Should the node accept the packet? -- Based on 
your definition of scope, it might well do it (because as long as it 
doesn't forward the packet, it's okay).

However, based on the current definition of scope, it shouldn't, because 
each of the interfaces is in a different zone.

I think the change you propose makes things way more complicated that 
simply keeping the scope definitions from RFC4007, and simply 
reclassifying ULAs et al.

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