You shouldn't assume a MAC isn't constant. Our students spoof their MACs all the time (thinking it will save them from getting a DMCA notice). The RFC suggests that DUIDs are stored in non-volatile memory or that an algorithm be used that can consistently reproduce the DUID (and IAID) for a system in the absence of persistent storage. For fixed hardware devices, I suspect most would opt for the use of DUID-LL type, which essentially the MAC with a DUID preamble, and doesn't need to be stored in memory since it's based on a MAC that can not be changed. It would be simple to create a DUID sticker at that point, even retroactively. I think the idea that DUID is random and getting worked up that it's not written on the side of the device is a little more FUD than fact. There _are_ things we need to address to make DHCPv6 easier to roll out (mainly on the server side), but just making bogus nitpick attacks distracts from the real issues, IMHO. On Mon, Jan 23, 2012 at 6:12 PM, Randy Carpenter <rcarpen@network1.net> wrote:
Controlled by software = not constant.
It is also not likely to be something that is knowable on a piece of electronic gear that is not a PC, nor will it be something that can be printed on the outside of the device, like most today.
-Randy
----- Original Message -----
Yes, DUID and IAID should be persistent on systems. If they are not then they are not following the RFC.
Note that bad practices, though, can remove that persistence (e.g. deleting the DUID, or replicating the DUID on other systems).
On Mon, Jan 23, 2012 at 5:56 PM, Karl Auer <kauer@biplane.com.au> wrote:
On Mon, 2012-01-23 at 17:26 -0500, Randy Carpenter wrote:
One major issue is that there is no way to associate a user's MAC (for IPv4) with their DUID. I haven't been able to find a way to account for this without making the user authenticate once for IPv4, and then again for IPv6. This is cumbersome to the user. Also, in the past there have been various reason why we want to pre-authenticate a client's MAC address (mostly for game consoles, and such, which have the MAC written on the outside of the machine). How can this be done with IPv6, which the DUID is not constant?
Perhaps I misunderstand you (or the RFCs) but it seems to me that the DUID *is* constant. Reading section 9 of RFC 3315, it's pretty clear that a DUID is generated once, according to simple rules, and does not change once it has been generated. Barring intervention, of course.
The problem is how to either find out ahead of time what DUID a client has OR how to impose a specific DUID on a client as part of provisioning it. Neither of those issues looks particularly intractable, especially if vendors start shipping with pre-configured DUIDs that are written on the boxes.
What do you mean by "authenticate"? Do you mean something like 802.1x?
Regards, K.
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Karl Auer (kauer@biplane.com.au) http://www.biplane.com.au/kauer
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-- Ray Soucy
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-- Ray Soucy Epic Communications Specialist Phone: +1 (207) 561-3526 Networkmaine, a Unit of the University of Maine System http://www.networkmaine.net/