Subject: Re: PANA FAQ

From: Thomas Narten <[email-masked]>
Date: Wed, 05 Jun 2002 06:41:26 -0400

"Alper E. YEGIN" <[email-masked]> writes:

> Thomas,

> > > I tend to agree. But the thinking has been that the host could possibly
> ICMP
> > > with IP address 0 to carry EAP payload. So it is possible that we
> > > could do authentication without the host having been assigned
> > > an address.
> >
> > I think this misses a basic point. If a server has to support multiple
> > concurrent operations with clients -- with each client using the all
> > 0's address -- the server needs some other way to distinguish
> > connections than IP addresses/port numbers. This would likely be
> > something based on the link-layer addresses used. But now, we no
> > longer have vanilla IP. We have IP plus the link-layer address. Note
> > this is an issue for all higher-layer "connection-oriented" protocols
> > (EAP would be one, in the sense that a connection consists of a
> > sequence of related packets belonging to a single EAP transaction). So
> > it does create complexity and would seem to lose a number of the
> > advantages of the pure L3 solution (which I thought was supposed to be
> > L2-agnostic).

> As I mentioned earlier, what is needed for this to work is same as
> what we are already doing for Mobile IPv4 in foreign-agent located
> care-of address case. Do we call Mobile IPv4 "not L2-agnostic"?

What specific parts of MIPv4 FA functions are you referring to above?
The fact that the FA sends out a packet for the MN on the local LAN,
even though the address of the MN implies that the MN is not on the
local LAN? Or something else? If just the former, the issues raised by
this are largely invisible to L3. I.e., it could be implemented by
installing a host route for the MN that points to the local net. 

> I acknowledge what it takes to make this work. But I don't agree
> this makes the solution L2-dependent.

> Other than having to cache the mac address of the incoming packet,
> and by-pass ARP/ND, what else is needed? What are the pure L3
> advantages we are losing?

Where PANA useage is seemingly different is that PANA will be
implementing a protocol that maintains state at the endpoints. A PANA
transaction will involve multiple packets, so those packets must be
identified as belonging to the same "connection". TCP/IP does this via
IP addresses and port numbers. If all zeros are used for IP addresses,
the information needed to identify a particular transaction is missing
and something else must be used. Using the link-layer addresses to do
this works (in theory), but would seem to require PANA-specific
changes, probably above the IP layer (e.g., UDP). This is a very
different L2-specific change than what I understand is needed by any
part of the MIP architecture. This is also something I am wary about
PANA taking on.

Thomas

---

From: "Alper E. YEGIN" <[email-masked]>
Date: Wed, 5 Jun 2002 11:06:17 -0700

Thomas,

> installing a host route for the MN that points to the local net. 

- Mobile IPv4 allows a MN to send a registration request with home address
set to 0.0.0.0 (NAI is used, and MN is requesting home agent to assign a
home address).
- Mobile IPv4 also allows privately addressed MNs with colliding IP
addresses to be able to registered via same foerign agent.

These cannot be handled with regular host routes, as IP addresses collide.

> part of the MIP architecture. This is also something I am wary about

This is same as what Mobile IP already deals with. Mobile IPv4
registration process is equivalent to PANA exchange as far as 
handling unspecified IP source address is concerned.

And it's already implemented, so it's not just theory.

alper