Subject: RE: address selection and DHCPv6

From: "Bernie Volz \(volz\)" <[email-masked]>
Date: Thu, 26 Oct 2006 16:03:26 -0400

I would think that how an address is assigned shouldn't enter into this.
I can't see that it matters.

What really matters is the lifetimes associated with the address. The
longest lifetime address is probably the best to use since it is the
most stable. [Ignoring privacy and other related issues.]

Perhaps this gets at what you want anyway, since manually assigned
addresses would presumable have the longest lifetime? 

- Bernie 

-----Original Message-----
From: Manfredi, Albert E [mailto:[email-masked]] 
Sent: Thursday, October 26, 2006 3:06 PM
To: Durand, Alain
Cc: [email-masked]
Subject: RE: address selection and DHCPv6

Except that from what others have said, that might not be the desired
goal. Perhaps for privacy or other reasons, a most stable address choice
might not be optimal.

I originally thought that would be the best choice, but ...

Bert

> -----Original Message-----
> From: Durand, Alain [mailto:[email-masked]] 
> Sent: Thursday, October 26, 2006 2:00 PM
> To: Bernie Volz (volz); James Carlson; Vlad Yasevich
> Cc: [email-masked]
> Subject: RE: address selection and DHCPv6
> 
> The question is not to get an absolutely stable address,
> but to make sure that in case multiple addresses are defined,
> the one with the highest likelyhood of stability is selected.

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From: Stig Venaas <[email-masked]>
Date: Thu, 26 Oct 2006 21:48:17 +0100

> most stable. [Ignoring privacy and other related issues.]

That's sort of what I thought at first as well. But if you use remaining
lifetime (and not the initial) you might easily end up in situations
where you fluctuate between several addresses. Not so good.

As an example, imagine two routers regularly sending RAs for one prefix
each, then you might end up always using the prefix you last got an RA
for, possibly changing every few seconds depending on the adv. rate.

Stig

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From: James Carlson <[email-masked]>
Date: Thu, 26 Oct 2006 16:57:58 -0400

> I can't see that it matters.

It matters only in that different assignment mechanisms have different
inherent stabilities:

	manual: "forever"

	DHCPv6: until the lifetime expires and the server refuses to
		renew

	stateless: until the network interface hardware is swapped

	temporary: "soon"

> addresses would presumable have the longest lifetime? 

Yes, that's equivalent.

-- 
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

---

From: Christian Huitema <[email-masked]>
Date: Thu, 26 Oct 2006 21:28:01 -0700

> 	stateless: until the network interface hardware is swapped

There is no inherent requirement that the host identifier be derived
from the interface hardware identifier. In a server environment, it
would make perfect sense to use another hardware identifier, or even a
logical identifier. That identifier would have pretty much the same life
time as a "manual" configuration.

-- Christian Huitema

---

From: Tim Chown <[email-masked]>
Date: Fri, 27 Oct 2006 09:43:33 +0100

> 	stateless: until the network interface hardware is swapped

There's a nice feature on Solaris for tokenised IDs such that you can
specificy manually the host part of an address, e.g. ::53 on a DNS server,
and the full address is formed from the RA information.   A colleague
did a similar implementation for Linux.    So an address can in principle
be partially manual :)

And DHCP can assign temporary addresses.

Alain sums it up best I think - you can only make a best guess.

-- 
Tim