Subject: Re: [mobile-ip] Mobile Routers support without optimization

From: James Kempf <[email-masked]>
Date: Fri, 17 Aug 2001 10:52:03 -0700 (PDT)

Alex,

>> An advantage of a NAT-like solution (I'm playing devil's advocate
>> here) is that it allows the devices behind the PAN to keep their CoA
>> while the multihomed host/mobile router moves.
>
>You say "keep" so it might mean the Home Address, not the CoA?
>

No, I meant the address on the PAN subnet. I'm assuming here that
the devices on the PAN subnet are not MNs in the MIP sense, or,
at least, that they are not going to move even if they are
MIP capable. It's a very limited case.

>NAT would disallow not only traffic from CN to MNN but also from HA to
>MNN, right?  Or you see traffic from HA to MNN as being tunnelled
>(through MR)?
>

Yes, that's right, but the devices don't need to talk to an HA (as above).

>> Additonally, the NAT can do route optimization with CNs, and traffic
>> from the PAN network is routable directly to the CN (i.e. not back
>> through the home network), so no triangle routing.
>
>What if the CN is itself behind an MR-NAT?
>

Hmmm, difficult. Needs more thought. There is a group working on
the problem of NATs around CNs and HAs, perhaps the solution
will fall out of that.

There is a third solution which came out of your previous email, namely
that the mobile multihomed host/mobile router does route optimization
with the CN but the CN tunnels traffic for the PAN subnet through
the MMH/MR. So the MMH is acting like a (dare I say it?) MIPv4
FA. In this case, you reduce the extent of the legs on
the quadralaterial route, since the tunnel to/from
the mobile subnet is through the MMH, which is probably a lot
closer to the mobile subnet than the HA.		

		jak

---

From: Alexandru Petrescu <[email-masked]>
Date: 17 Aug 2001 20:57:50 +0200

James Kempf <[email-masked]> writes:
> the devices on the PAN subnet are not MNs in the MIP sense, or, at
> least, that they are not going to move even if they are MIP
> capable. It's a very limited case.

PErfect for our discussion, this is what I have in mind too.

> the problem of NATs around CNs and HAs, perhaps the solution

Aha, eager to see it, thanks for indication.

> There is a third solution which came out of your previous email,
> namely that the mobile multihomed host/mobile router does route
> optimization with the CN but the CN tunnels traffic for the PAN
> subnet through the MMH/MR.

Gee, I thought _you_ had this in mind when writing previous messages.

Also, tunnelling could mean tunnelling, or routing heading?

> So the MMH is acting like a (dare I say it?) MIPv4 FA.

Well, yes, there are similarities between MMH/MR and FA's, except they
move.  More generally, Thierry and HMIPv6 authors see a similarity
between MMH and MAP extended mode.

When thinking about MMH we can take additional requirements that stem
from the elimination of FA and the arguments against MAP.

Thanks for your useful insights,

Alex

[NAT: in my understanding, an address behind a NAT is not routable on
 the Internet and it's reserved as such.  An address behind an MR
 should be routable at least between CN and HA.  Maybe in our context
 the MR should use a sort of address translation (could be
 tunnelling), maybe should not call it NAT]