Subject: [MOBILE-IP] Is it possible?

From: Ren-Shiou Liu <[email-masked]>
Date: Tue, 25 Jan 2000 21:28:11 +0800

Hello everyone,
   I was wondering if it is possible for a mobile node, with overlapping
wireless cells, to receive multiple agent advertisements from different
foreign agents? If it is possible, what should the mobile node do? And
dose this imply that the underlying link layer has the capability of receiving
data from multiple agents? Thank you for your reply!

--
Jason Liu, Parallel and Distributed Processing Lab.
Dept. of Computer Science & Information Engineering
National Chiao-Tung University, Hsinchu, Taiwan
E-Mail: [email-masked]

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From: Dan Forsberg <[email-masked]>
Date: Wed, 26 Jan 2000 11:10:14 +0200

rsliu>    I was wondering if it is possible for a mobile node, with
rsliu> overlapping wireless cells, to receive multiple agent
rsliu> advertisements from different foreign agents? If it is
rsliu> possible, what should the mobile node do? And dose this
rsliu> imply that the underlying link layer has the capability of
rsliu> receiving data from multiple agents? Thank you for your
rsliu> reply!

The agent advertisements are sent to broadcast or multicast address. Thus,
if the MN is one hop away from the FA, it is possible for the MN to hear
more than one FA simultaneously (IP routing).

There is no need for simultaneous bindings for this kind of behaviour. If
we need to establish connections with both FAs, it would be necessary.

To the handoff discussion. When the MN hears multiple FAs at the same
time, it has the possibility to choose the best one. The decision for the
"best" node is problem for the MN. If received signal strengths can be
obtained from the link layer, the decision becomes easier. Thus, also the
handoff decisions can be made much more faster than the agent
advertisement interval.

The hierarchical Dynamics - HUT Mobile IP uses the link layer signal
quality information of WLANs and the handoff decisions is based on that in
the MN. In addition the ability of the MN to hear multiple FAs at the same
time enables soft handoffs and thus packet loss is minimized. No buffering
nor multicasting type scenarios are needed to support smooth handoffs with
soft handoff. Simple and effective ;).

Dan

--
 [email-masked] <http://www.iki.fi/dan.forsberg>
 Dynamics - HUT Mobile IP <http://www.cs.hut.fi/Research/Dynamics/>

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From: Qiang Zhang <[email-masked]>
Date: Wed, 26 Jan 2000 10:30:38 -0500

Jason, I remember there was a thread "CDMA misinterpret" on the list(around
last August) discussing the cellular underlayer link impact which you might
be interested.

>From my understanding, MIP itself has no problem to maintain multiple
bindings, however a lot wireless mediums so far can't support the happening
of multiple bindings via the same adapter, i.e. in the 802.11 LAN or the
Cellular environment, you are not able to receive packets simultaneously
from 2 access points or base stations.

Chiang