Subject: IA identifiers

From: Ralph Droms <[email-masked]>
Date: Thu, 01 Feb 2001 17:58:02 -0500

At the WG meeting in San Diego, we discussed how DHCP clients and servers 
can identify Identity Associations (IAs).  The two proposals on the table 
are to use a DHCP Unique Identifier (DUID) or to use the interface 
identifier portion of a host's link-local  address along with a prefix from 
the link to which the host is attached.

In short summary, the difference between the two schemes is the assumptions 
about the global identity an IA.  If we use a DUID to identify an IA, DHCP 
servers can assume that an IA with the same DUID that arrives from a new 
link (from a different link than it was originally associated with) is 
really the same IA, and the servers can take action on that assumption.  If 
we use <interface identifier, prefix>, a roaming IA cannot be identified.

We have not yet fully defined how hosts might be able to generate a DUID 
that can be guaranteed to be unique among all DHCP clients.  We have 
operational experience with DHCPv4 that assuming MAC addresses (e.g., from 
a NIC) are unique is a bad assumption, and that identifier clashes among 
DHCP clients in DHCPv4 has been a problem.

We need to resolve this issue before the spec can go to WG last call.  I 
want to kick off the discussion by giving the WG a chance to get the issues 
out on the table before we get to making a decision about which strategy to 
use.  So, here are a couple of questions to open the discussion:

* Does this message accurately summarize previous WG discussion
   on the issue?
* Are there other strategies for IA identification that we
   should consider?
* What are all of the effects of choosing one or the other
   (or some entirely different) mechanism for IA identification?

- Ralph

---

From: [email-masked]
Date: Fri, 02 Feb 2001 08:10:28 +0900

>DHCP clients in DHCPv4 has been a problem.

	sorry if I don't follow past discussions well.
	if there's no concrete algorithm for generating DUID, i think the
	discussions will not be useful...  i'd suggest either
	(1) define DUID generation algorithm and then discuss between
	    DUID and interface ID,
	(2) use inteface ID

	(i believe it so hard to define DUID with total global uniqueness -
	it is almost impossible, I think)

itojun