Subject: RE: [mobile-ip] some questions about draft-ietf-mobileip-fast-mip v6-04

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Mon, 6 May 2002 17:01:00 +0200

> I think you're missing one really important
  > ingredient here: the mobile node wants to be able
  > to have some say in what the next AR might be
  > too. In particular, I really, really, want to have
  > my mobile node be able to, say, tell the cellular
  > router to create a tunnel to a COA on my home
  > 802.11. In that case, the cellular router knows
  > nothing at all about my 802.11; it's the MN that
  > figures this out somehow. 

=> Exactly. Abstracting it even more, if we want
to have a truely L2 independant solution, the 
MN MUST be involved in deciding where it's 
going. The AR can accept/reject that decision, 
but the MN has to be involved.

Hesham

---

From: "James Kempf" <[email-masked]>
Date: Mon, 6 May 2002 09:48:12 -0700

Hesham/Michael,

>   > figures this out somehow.

In my note, I said this about intertechnology handover:

      Note that this method is particularly well suited to
intertechnology
      handover, where the mobile must be involved in the handover
decision
      regardless of the performance implications, because only the
mobile
      knows which interfaces it currently has active or even installed
(for
      PCMCIA cards).

So I agree that there needs to be mobile involvement when there is
intertechnology handover, such as between cellular and 802.11.

> but the MN has to be involved.

The purpose of the L2 triggers draft
(draft-manyfolks-l2-mobile-req-04.txt is to define an abstraction of the
information needed by IP from the link layer for fast handover. The
intent is to allow the specification of the handover protocol to be
independent of specific Layer 2 technologies. So I do agree about the
need for a technology independent specification of the fast handover
protocol.

However, for intra-technology handover, eliminating signaling to and
from the mobile immediately prior to handover when radio conditions are
deteriorating is crucial for consistent, reliable handover performance
if the wireless protocol provides the access router with the proper
handover sequencing information, as defined in the L2 triggers draft. On
IS-2000 RAN (the only radio protocol where we could implement both
mobile-controlled and network controlled handover to compare them),
network-controlled handover consistently loses about 1-2 packets whereas
mobile-controlled loses 11-20 or more, sometimes over 25 if the handover
signaling between the mobile node and the access router fails because
the mobile moves too quickly. As I mentioned in my note, this does not
preclude the mobile being involved at an earlier stage, considerably
prior to the handover itself, or afterwards when radio conditions and
the mobile's movement pattern make the Layer 3 connection more reliable,
but it does argue, and quite strongly in my opinion, for limiting the
mobile's involvement immediately prior to the handover, if the radio
protocol makes this possible.

            jak