Subject: DHCP and ATM

From: Tim Salo <[email-masked]>
Date: Mon, 9 Nov 1998 11:43:46 -0500 (EST)

Is anyone running, or has anyone looked at, DHCP over ATM and other
non-broadcast, multiple-access (NBMA) networks?

Have any Internet Drafts or other documents been written on this topic?

Thanks,
	-tjs

---

From: "Bud Millwood" <[email-masked]>
Date: Thu, 12 Nov 1998 16:47:03 -0500 (EST)

> non-broadcast, multiple-access (NBMA) networks?

Tim:

We have a customer that uses our BOOTP server with an ATM network. I'm not
overly familiar with ATM, but I understand that he was using
Classical-IP-over-ATM. The bottom line for him was that our unicast response
could not be directed back to the hardware address our server received, but
instead had to go to an arbitrary hardware address. We provide a
"pseudo-option" for configuring this.

This has some severe problems. He (our customer) is using BOOTP, which is
static addressing, so pre-configuring an arbitrary reply address is fine.
For dynamic addressing this would be a problem.

I understand that a "real" ATM address is 40 octets. The Client Identifier
field of a BOOTP/DHCP packet could easily carry this address, but I'm not
sure how the server should respond. Since broadcasting is out of the
question, I suppose you'd have to have an IP stack that understood the
notion of a 40 octet hardware address. Although our BOOTP/DHCP products can
place an entry in the NT arp cache, I doubt it would accept a 40 octet
monster.

For what it's worth, our "BOOTP Server NT" product does support static DHCP
and Classical-IP over ATM.

We are finishing a new DHCP server for NT and I'd be more than willing to
incorporate anything useful you could add concerning ATM.

Bud Millwood
Weird Solutions, Inc.
http://www.weird-solutions.com
mailto:[email-masked]
tel: +46 70 566 7803
fax: +46 8 758 3687