Subject: [mobile-ip] Question about draft: Generalized Key Distribution Extensions for MiP

From: Alpesh Patel <[email-masked]>
Date: Thu, 12 Jul 2001 13:39:22 -0700 (PDT)

Hi,

I am a late follower of this draft and our team had a question about why
reinvent the wheel about key distribution. I was wondering why not use
IKE for Key distribution and define a new Domain of Interpretation for
MobileIP? 

-alpesh

---

From: Pat Calhoun <[email-masked]>
Date: Fri, 13 Jul 2001 10:14:00 -0700

> IKE for Key distribution and define a new Domain of Interpretation for

Good question. The issue is that the security model, at least in MIPv4,
doesn't lead itself nicely to IKE. Consider the following example, which
is typical of an IKE scenario:

    MN ------------> CN
          IKE SA

Now, consider a MIPv4 scenario, where the gen key draft comes into play:

    MN ------------> FA ----------> HA
        MN-FA SA         FA-HA SA
       --------------------------->
                 MN-HA SA

So the main difference here is that a security association is created 
between all entities in the network. Certainly, the mobile could setup
an IKE SA with the FA, and the FA with the HA. However, how can the MN
setup an IKE SA with the HA, when the FA must process the protocol at
the application layer. So, clearly some authentication is needed at the
app (Mobile IP) layer.

So, what this draft does, is allow a mobile node to get keying material
that will be used to authenticate messages, using all three SAs above.

Lastly, there are cases where a Mobile Node doesn't have a home address
(nor a local address), and the MIP messages are used to allocate an address.
So, IKE with a NULL IP address is not something that would work quite well.
You would end up having to run IKE with NULL, secure MIP messages, get
an address via MIP, and then run IKE again with the new address. of course,
this assume that IKE would even work in the MIP message exchange, which I've
already proven it doesn't.

Hope this answers your question,

PatC