[Dhcpv6bis] Changing default DUID to DUID-LL?

[Tomek Mrugalski <[e-mail]>]

I recall we did talk about this briefly, but I can't find anything
specific posted to dhcpv6bis.

Once in a while sysadmins keep asking why DHCPv6 is using DUID-LLT as
default, rather than just LL. Here's an example of such question asked
last week:
https://www.facebook.com/groups/2234775539/permalink/10154080188010540/
(if you don't have facebook account, you can still see the discussion by
clicking X comments link).

The details vary, but the general objection is still the same. There's a
large enterprise or similar organization and the sysadmin would like to
know DUIDs of the devices he's about to plug into his network to do host
reservation, access control or provide some options on a per host basis.
He can't do that without powering up every device and letting it
generate its LLT duid.

There are several twists to this. First, some people claim it's
difficult to extract generated DUIDs from many operating systems, so
cases where users themselves are expected to provide their DUID, even if
the device was booted up already, are problematic for users to handle.

Another objection is that most hardware these days have MAC address
printed on it. Vendors can't really print DUIDs as they are not known
during manufacturing phase.

As I understand it, the original rationale for using LLT rather than LL
as default was to avoid cases when switching faulty NIC would make the
client to change its DUID. This is very 1990s. If you disagree with
this, when was the last time you replaced faulty interface card? Also,
the mechanism we have right now - generate the DUID and store it -
effectively solves the concern.

So, what's your opinion on making the DUID-LL the default for regular
devices (i.e. those with clocks and stable storage for generated DUIDs)?

Tomek