Hi Pete,
I think the source of the confusion is the use of DHCP options. The
initial version of this I-D did not propose to use DHCP options at
all.
The proposal contained a few possible host config parameters that we
would have defined. However, someone saw the light, and suggested
that instead of redesigning the host config options from scratch, why
not we used the options and the format of the options carrying config
info as defined in DHCP. It made sense; hence we decided to accept
that approach.
Now, I see that people are mixing the use of DHCP protocol with MIP4
host config options. I think this is a digression that we should
avoid.
We need to understand the scope of the I-D. It does not rule out
other ways to do host configuration when the MN is using MIP4. It
defines _a_ way that is Mobile IP specific. It is also the most
efficient one from the number of round trips point of view.
When you say that running DHCP inside MIP4 tunnel allows for a single
protocol to be used whether the MN is at home or visiting, I have a
question. How is it possible for the MN to fetch config info from the
visited network when RT is negotiated and enforced at the FA?
BTW, the approach specified in the draft-ietf-mip4-gen-ext-03.txt
allows the use of a single protocol i.e. MIP4 to be used to fetch
config info from home and visited networks, not to mention with fewer
number of messages.
Another issue that we need to think about the use of DHCP inside MIP4
tunnel is security. We cannot prohibit the MN to run DHCPINFORM only,
right? The MN may start doing IP address config (lease and release).
How to secure these DHCP messages? If we intend to only allow the MN
to send DHCPINFORM, how do we prevent it from sending other DHCP
messages?
AFAIK, RFC 3118 is not widely implemented and used. Even if it is, we
can't expect the MIP4 implementations to start implementing RFC 3118
just to get a few config info from the home domain.
Regards,
Kuntal
-----Original Message-----
From: McCann Peter-A001034 [mailto:pete.mccann at motorola.com]
Sent: Tuesday, July 31, 2007 9:01 AM
To: mip4 at ietf.org; dhcwg at ietf.org
Subject: [Mip4] draft-ietf-mip4-gen-ext-03.txt
A question has arisen during the last call for
draft-ietf-mip4-gen-ext-03.txt.
The draft includes the following text:
There are mechanisms
such as DHCP for the mobile node to configure information from
the foreign network, but not from the home network when the
mobile node is not attached to the home network.
However, this may not be strictly true. In particular, it might be
possible to use a DHCPINFORM message through the tunnel that was
established with Mobile IP, thus eliminating the need to encode DHCP
options inside Mobile IP messages.
This would allow for a single configuration protocol to be used
whether the MN is at home or visiting.
I think we may have touched on this question during our last
chartering discussion but we might not have explored all the
ramifications. Please, if you have an opinion either way express it
now and give some background as to why you think so.
It is possible that we might turn this draft into a BCP-like
document
for how to configure and run DHCP over the tunnel to the home
network.
-Pete
