Subject: RE: [mobile-ip] IPv4 Fast Handover Support for 802.11

From: "Karim El-Malki (ERA)" <[email-masked]>
Date: Mon, 3 Dec 2001 11:06:15 +0100

James,

Why does draft-ietf-mobileip-lowlatency-handoffs not support 802.11?
PRE-REG can be applied to 802.11 using the mobile-initiated part with
a mobile trigger. The mobile trigger in this case would likely be based
on signal strength measurements in the MN and the FA address could be
embedded in the beacon. So I disagree that low latency needs to be fixed
for 802.11. What you may have intended is that POST-REG as it is in the
draft cannot be used with 802.11, but low latency has a solution which
can be used for 802.11 already.

/Karim

 > -----Original Message-----
 > From: James Kempf [mailto:[email-masked]]
 > Sent: den 3 december 2001 00:57
 > To: [email-masked]
 > Subject: [mobile-ip] IPv4 Fast Handover Support for 802.11
 > 
 > 
 > Folks,
 > 
 > As some of you may have noticed,
 > draft-ietf-mobileip-lowlatency-handoffs-ipv4.txt does not 
 > support fast
 > handoff for the current 802.11 MAC. While the 802.11 spec is always
 > subject to change, it may take awhile and the IPv4 fast 
 > handoff work is
 > supposted to be immediately deployable. We've done a short 
 > proposal for
 > how to support fast handoff for 802.11 as it currently 
 > exists, it's at
 > http://geocities.com/kempf42/draft-kempf-mobileip-postmit-han
dover-00.tx
t, it fits into the existing
low latency framework fairly smoothly. Sorry we couldn't get this in on
time, but we just figured it out in the last couple days. This proposal
also has some other uses, re the low latency draft, and it is just to
get the conversation started about how to fix low latency for 802.11
(that is, we don't necessary expect the WG to accept it as is, but we do
want to get the problem solved).

            jak

---

From: "James Kempf" <[email-masked]>
Date: Tue, 4 Dec 2001 02:58:21 -0800

Karim,

The MN in 802.11 does a reassociation without any trigger to Layer 3, at
least, that is how it currently works.
One could make the modification you suggest below, however, it would be
a change in the way the 802.11
protocol works. If you simply modify the driver to look at signal
strength, then deliver a pre-Layer 2 trigger
based on that, the MN may very well decide to move to another Access
Point if the signal strength of that
AP meets the criteria. As far as I understand, there is no way given the
current 802.11 protocol to fix the new AP in advance of the Layer 2
handover.

At best, given current 802.11, one could imagine delivering a pre-Layer
2 trigger as soon
as the MN sent the 802.11 reassociation message (the Link Down trigger),
but this would not give Prereg
enough time to complete any messaging through the old AP.

                jak