Subject: Re: Re: DHCID and the use of MD5 [Re: Last Call: 'Resolution ofFQDN Conflicts among DHCP Clients' to Proposed Standard]

From: "David W. Hankins" <[email-masked]>
Date: Mon, 28 Nov 2005 23:18:28 +0000

On Mon, Nov 28, 2005 at 05:20:09PM -0500, Bernie Volz (volz) wrote:
> Yes, I can.
> 
> The ISC's DHCP server (www.isc.org) does this (I'm not sure whether it
> uses MD5 to encode the client identity or not). Ted might know for sure.

It does, though it only encodes the client identity (client identifier
option or chaddr), it does not include the FQDN like the current DHCID
draft does.

There are a few niggling bits that are different, and obviously
incompatible (not just because it's encoded as hexadecimal in a TXT
record), but on all points that are topical to this discussion it's
the same.

-- 
David W. Hankins		"If you don't do it right the first time,
Software Engineer			you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins

---

From: Ted Lemon <[email-masked]>
Date: Mon, 28 Nov 2005 16:32:40 -0700

The Nominum DHCP server (DCS) supports the exact mechanism described in the 
collection of documents, except that the data is stored in a TXT record 
rather than a DHCID record, because we are waiting on the DHCID record.   We 
also implement the older version of the protocol that the ISC server 
supports, which as David says is only slightly different than the current 
spec.

---

From: Harald Tveit Alvestrand <[email-masked]>
Date: Tue, 29 Nov 2005 07:40:08 +0100

Thanks - these responses point out very clearly that the mechanism is being 
used as described, *except* for the bit that's contentious (use of MD5 for 
information hiding).

This means that we will not have a backwards compatibility issue with the 
installed base if we change the format of the record, but *will* have a 
procedural compatibility issue if we don't keep the property of "you can 
know the expected content of the record without fetching it".

                   Harald

--On mandag, november 28, 2005 17:20:09 -0500 "Bernie Volz (volz)" 
<[email-masked]> wrote:

> Harald:
> As does Cisco's Network Registrar (though it presently doesn't encode
> the data using MD5).
>
> And, I'm pretty sure several other DHCP vendors do this -- though
> whether they're using MD5 or not I can't be sure.
>
> These servers are in production all over and have been doing this for
> many years.