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> Thu, 07 January 2021 21:56 UTC

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To: Brian E Carpenter <brian.e.carpenter@gmail.com>, Philip Homburg <pch-ipv6-ietf-7@u-1.phicoh.com>, ipv6@ietf.org
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From: Fernando Gont <fgont@si6networks.com>
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Date: Thu, 7 Jan 2021 18:55:38 -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 7/1/21 17:31, Brian E Carpenter wrote:
> On 08-Jan-21 00:52, Philip Homburg wrote:
>>> I have an idea for what to call ULA's scope without redefining global scope
>>> in RFC4007, how about we call ULA's scope "pseudo-global" scope.
>>
>>> What do other people think?
>>
>> In my opinion we need to kill the RFC 4007 scope concept.
>>
>> We can define for example 'address types' that have no scope, but as a way
>> to label different types of addresses.
> 
> This.

Me, as long as the outcome is clear, I'm fine.

("scope", as a conceptual property of addresses doesn't seem bad.  You 
can talk about the scope of IPv5 addresses (link-local, private/local, 
global) in IPv4, too).

That said, removing the concept of "scope" would probably need more 
things to be re-worked -- not necessarily bad, though.



> Link-local needs an interface ID or interface index, which is meaningless outside the host.
> 
> All other unicast addresses are routeable, and do not require an associated interface ID. The range of reachability is always administratively defined, with default behaviours (ULA = limited domain reachability, GUA = global reachability).

Me thinking out loud:
What about the case where you have a host with two interfaces, each with 
one different ULA prefix, and you need to send packets to a destination 
ULA prefix, that is totally different from the two you're using?

Another similar case would be a host with two interfaces, global 
addresses on each, that has to send packets to a ULA prefix.

It would seem to me that in wuch cases, you'd need a way to specify an 
interface.

(Not sure if, conceuptually speaking, not having an address configured 
for the ULA prefix you're trying to communicate with, means that you're 
not part of the "zone", and hence, that you're on your own)


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