Subject: RE: address selection and DHCPv6

From: "Bernie Volz \(volz\)" <[email-masked]>
Date: Thu, 26 Oct 2006 12:37:17 -0400

Whatever technique you use will likely never guarantee a completely
stable address.

Manually assigned is just as good (or bad) as DHCPv6 because both depend
on some type of stable storage (so yes there is hardware associated with
it). (Well, I guess you could always rely on a human to type in the
manually assigned address on a boot but that is unlikely to be desirable
and may not be as reliable).

- Bernie 

-----Original Message-----
From: James Carlson [mailto:[email-masked]] 
Sent: Thursday, October 26, 2006 12:31 PM
To: Vlad Yasevich
Cc: Durand, Alain; [email-masked]
Subject: Re: address selection and DHCPv6

Vlad Yasevich writes:
> The concept that a DHCP address is more stable then
> EUI64 base address is flawed in my opinion.  Both depend
> on a piece of hardware that can fail or be changed.

That's incorrect.  See RFC 3315 -- DUIDs are required to be stable,
even if the hardware is changed.

> I guess manually configured addresses are a bit more
> stable.

Indeed.

> The rules as specified now tend to be agnostic more or
> less.  They would work no matter how things are set up.
> (there are exceptions, such as ULA). 

More or less?  I don't think the temporary address decision is a small
matter, and I do think this issue is related to that one.

> Of course, implementations may override Rule 8 (longest
> prefix match) with something better/different.  I wouldn't
> object as strongly to something like this:
> 
>    Rule 8 may be superseded if the implementation has other means of
>    choosing among source addresses.  For example, if the
implementation
>    somehow knows which source address will result in the "best"
>    communications performance or knows relative stability of addresses
>    and wants to select a more stable one.

I'm no longer quite convinced that this sort of thing is right.
Placing it above rule 8 means that prefix routing issues are ignored.

It seems to want to go below rule 8 in priority order.  But I guess I
could still go along with that as a compromise.

-- 
James Carlson, KISS Network                    <[email-masked]>
Sun Microsystems / 1 Network Drive         71.232W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.496N   Fax +1 781 442 1677

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From: James Carlson <[email-masked]>
Date: Thu, 26 Oct 2006 14:41:04 -0400

> and may not be as reliable).

Both are unlike stateless address autoconfiguration in that the lower
64 bits of the address aren't a EUID, and thus aren't tied to
*replaceable* hardware, such as an Ethernet interface.

That's the key point.