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

From: James Kempf <[email-masked]>
Date: Thu, 16 Aug 2001 10:23:50 -0700 (PDT)

Hi Erik,

Thanx for the reply.

>> What does a MR being "at home" mean? A router typically bridges subnets
>> and so it is not entirely obvious to me what it means for a MR to
>> have a home agent nor what the router's home subnet would be.
>
>Depending on approach to the problem people might come up
>with different definitions. In the PAN case (and perhaps other scenarios)
>it probably makes sense to define the "home link" as the link
>where the routers live that the MR has routing adjacencies.
>Essentially those routers at home trust the MR to announce routes for
>at least its mobile subnet.
>
>In order for the MR to tell those routers at home its current location
>the MR need some identity. I think the home address could be such an identity.
>

In the PAN scenario, the PAN always gets access to the wired network through 
some other radio or wired link, correct? If so, the PAN interface itself is 
never connecting into the wired network directly.

In that case, as Mattias suggested, a NAT on the PAN side would work
just fine (yes, I know NATs are evil, but they are a practical,
short term solution that should be discussed).

		jak

---

From: Erik Nordmark <[email-masked]>
Date: Fri, 17 Aug 2001 10:23:16 +0200 (CEST)

> never connecting into the wired network directly.

I don't know exactly what a "PAN interface" is so let me try to restate
what you are saying.

A PAN is an IP link. There is an IP router between the PAN and the rest
of the network.
Thus the devices on the PAN (other than the router) never connect directly
to any other link - they always go through the router.

If that is what you are saying then, from my IP centric view of the world,
I think that is a very reasonable view of a PAN. In fact it is the view
I'd prefer.

> short term solution that should be discussed).

Whoa - what a can of worms. Should we really dive into that one?

NAT has nothing inherently to do with PANs - this argument is no
different than NAT being useful in a home environment.
And NAT assumes that the devices on the PAN are client-only i.e. they
only initiate communication.
I for sure want the model to allow devices on the PAN to be able to
do peer-to-peer communication with other devices elsewhere in the network
i.e. allowing other nodes to connect to the devices in my PAN.

  Erik

---

From: Mattias Pettersson <[email-masked]>
Date: Fri, 17 Aug 2001 14:10:20 +0200

> Whoa - what a can of worms. Should we really dive into that one?

So you prefer this Mobile IPv6 can of worms instead? I wouldn't say we
are completely clean here either... :)

We are a bit more end-to-end, but NAT has obviously been more deployed
than Mobile IP and seems to be of some use at least.

Sorry for being ironical (or cynical). I don't support NAT, but it could
solve a few things here:
 - No complex trust model, the mobile network will look like a single
MN.
 - No additional support in CNs.
 - No routing problems at home with other routers.
 - As the mobile network is maybe very small, it will require little
configuration.
 - If the user wants e2e, he could use the MR.

Now, if mobile-ip was moderated, I would have been kicked off this list
by now. ;) Should have use my hotmail account...

> different than NAT being useful in a home environment.

NAT is just a quick short-term solution. But a PAN such as you describe
it does have a number of similarities with home environments.

> only initiate communication.

There are ugly tricks for this too.

> i.e. allowing other nodes to connect to the devices in my PAN.

/Mattias

---

From: Erik Nordmark <[email-masked]>
Date: Mon, 20 Aug 2001 12:04:13 +0200 (CEST)

> are completely clean here either... :)

This is getting into discussing the pro's and con's of NATs which is,
as far as I know, not the subject of trhe mobile-ip mailing list.
Thus I expect the chairs to cut this discussion short :-)

IMHO I think there is a very big difference between the transparency
(see RFC 2775) provided by IP end-to-end and the attempt at NAT boxes
to provide support for some set or some classes of applications.

> than Mobile IP and seems to be of some use at least.

What aspect of Mobile-IP is not end-to-end transparent IP?

  Erik

---

From: Mattias Pettersson <[email-masked]>
Date: Mon, 20 Aug 2001 15:09:43 +0200

> What aspect of Mobile-IP is not end-to-end transparent IP?

I shouldn't have brought this issue up, of course.

The route optimized Mobile IPv6 is a good thing. It is e2e, the
end-nodes are fully aware of what is happening. There are no nodes in
between that have essential functionality (except when a HA is initially
needed as a consequence of CN-initiated traffic).

Mobile IPv6 without route optimization is hiding to the CN that there is
a HA in between. The HA is doing proxy ND and proxy DAD for the MN. We
play make-believe that the MN is always at home. We do it for global and
site-local addresses, but not for link-local.

Mobile IPv6 is a pretty good protocol, but I think it suffers from that
we want to emulate that the MN is a fixed node. My recommendation: hide
movement less. Let end-nodes be aware of mobility.

Anyway, there are different proposals for things in this direction. I
should stop boring you [the WG] with these insults.

/Mattias

---

From: Erik Nordmark <[email-masked]>
Date: Mon, 20 Aug 2001 15:22:49 +0200 (CEST)

> I shouldn't have brought this issue up, of course.

Of course. :-)

You seem to argue that a different approach to mobility can be made
better than mobile IP as currently defined. (I may or may not agree with
that - it is not important for this point.)

This is very different than in the mail I replied to where
you seemed to say that Mobile IP was similar to NAT in some respects.

As far as I can tell, mobile IP is transparent to IP packets
but you seem to be claiming otherwise?

  Erik

---

From: Mattias Pettersson <[email-masked]>
Date: Mon, 20 Aug 2001 15:40:13 +0200

> that - it is not important for this point.)

That was a bonus.

> but you seem to be claiming otherwise?

The triangular routed case below has a box in the middle that is
invisible to the CN (like a NAT). The packets pass though unmodified (HA
is not that evil), but some packets are not forwarded (link-local).

/Mattias