Subject: [dhcwg] draft-ietf-dhc-leasequery-06 clarification

From: "Kostur, Andre" <[email-masked]>
Date: Thu, 27 Nov 2003 09:42:36 -0800

I think that the draft has a potential ambiguity in handling option 82 in
the leasequery replies.

RFC 3046 mandates that option 82 SHOULD be the last option in the reply
packet.  The leasequery draft only says that it will be included in the
packet if the relay requested option 82 (and assuming that the DHCP server
has information to put in option 82).

So, from a leasequery perspective, if the server has data to put in option
82, where should the draft specify that the option should be placed within
the packet?  Should it also specify that option 82 SHOULD be the last option
within the packet, and may not be placed in the overloaded fields?  Or
should the draft specify that option 82 within the leasequery reply may be
anywhere within the options field?

My opinion on the matter: I think that the presence of option 82 within a
leasequery reply serves a different purpose that the presence of option 82
within a "normal" DHCP reply.  Within a normal reply, option 82 needs to be
able to be removed by the Relay without potentially disrupting any 3118
authentication that may be in use.  Also option 82 may be carrying some sort
of "routing" information for where this reply is really destined for (which
circuit ID, which remote ID, etc).  However in a leasequery reply the
presence of option 82 is simply "dead data" that is being passed from the
DHCP server to the relay.  It has no more significance within the packet
than the presence of, say, option 3.  Given these points, I would suggest
that the draft specify that the option 82 inserted in a leasequery reply
does not have to follow the rules of 3046, but is to be handled like any
other option (order & positioning is irrelevant, it may be placed in
overloads, etc...).

And come to think of it, another wrinkle within this mechanism: what would
be the correct behaviour for a DHCP server which receives a leasequery that
has an option 82?  According to 3046, the DHCP server would be required to
echo it back to the client, but that would overwrite (or append to) the
existing option 82 (which is the one that was being sent back as part of the
leasequery reply).  Should the draft specify that a relay MUST NOT supply an
option 82 in its leasequery?