RE: [dhcwg] Internet Drafts to be reviewed by the dhc WG

It says "Entities using the Midcom Protocol need to know the presence of
Midcom middleboxes, such as firewalls and network address translators,
in order to enable communication across theses devices." in the abstract
of the draft. So, it looks like we're in for NAT with IPv6 ...

I think the WG should take up the issue of how best to handle options
that want to specify either or both domain names and IPv6 addresses. It
seems to me silly to have TWO options for every time this needs to occur
(as is the case in this midcom draft). And, this mechanism provides no
way to specify the preference between the two - order can be used within
each option to specify which to try first, but it can't be used across
the options. So, it is then left up to the draft (or implementor) to
pick which to use first.

The obvious answer would be to use a sub-option technique or a flag byte
before either an address or domain name. Something like:

	DHCP option (either 8-bits or 16-bits)
	Option length (either 8-bits or 16-bits)
	Encoding type (8-bits? - 0 for domain name, 1 for IP addresses)
	Encoding length (8 bits?)
	Data (either domain name or address)
	Encoding type (8-bits? - 0 for domain name, 1 for IP addresses)
	Encoding length (8 bits?)
	Data (either domain name or address)
	...

In the cases where only one type of encoding is used, this would cost 2
extra bytes. In the cases where multiple encodings are used, this would
either be the same length as the two-option method or potentially save
two bytes (depending on the encoding type/length field sizes).

Note: It would also be possible to specify IPv4 AND IPv6 addresses (1
for IPv4 address, 2 for IPv6 addresses for the encoding type, for
example).

- Bernie

-----Original Message-----
From: dhcwg-admin@ietf.org [mailto:dhcwg-admin@ietf.org] On Behalf Of
Tim Chown
Sent: Wednesday, March 31, 2004 3:51 PM
To: Ralph Droms
Cc: dhcwg@ietf.org; margaret@thingmagic.com; narten@us.ibm.com; Melinda
Shore
Subject: Re: [dhcwg] Internet Drafts to be reviewed by the dhc WG

On Wed, Mar 31, 2004 at 01:24:05PM -0500, Ralph Droms wrote:
> There are a couple of Internet Drafts under review by the midcom WG 
> that specify new DHCP options:
> 
> draft-tran-midcom-dhcpv6-option-00.txt

So this one assumes that IPv6 NATs exist and midcom will handle IPv6 NAT
traversal?  Or s midcom for IPv6 a means to configure the middlebox for
other ALG or firewall purposes?

Luckily I don't think Keith Moore is on the dhc WG list :)

Tim

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