Subject: link layer feedback

From: Kevin Purser <[email-masked]>
Date: Thu, 05 Aug 1999 10:35:34 +0200

Hello All,

I am attempting to augment an existing AODV implementation with the
Lucent IEEE 802.11 cards to utilize link-layer feedback (to detect
broken links and such), and at present, I'm completely unaware where to
find information on this topic.  I would greatly appreciate if someone
could
point me in the right direction to find out how to obtain such feedback
from the driver (or perhaps more needs to be done?).

Thanks!
Kevin

--
==========================================
Kevin Purser
Ericsson Radio Systems AB
Switchlab
Varuvägen 9B
S-126 25 Stockholm, Sweden
Phone: +46 (08) 719 16 07
Fax:   +46 (08) 719 66 77
==========================================

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From: "Samir R. Das" <[email-masked]>
Date: Thu, 5 Aug 1999 10:36:15 -0500 (CDT)

Kevin:

Which OS are you using? I looked at the Lucent Wavelan PCMCIA card
drivers for Linux in the past. I believe that there are
transmit_failure exceptions (or something very similar) generated at
the driver that you can easily catch and pass on to the routing layer.
This was for the first generation cards though.

This would require some (simple) modification in the driver code though.

Samir Das

--

Kevin Purser writes

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From: Jari T Malinen <[email-masked]>
Date: Thu, 5 Aug 1999 21:10:44 +0200 (EET DST)

> from the driver (or perhaps more needs to be done?).

Hello, Kevin,

We are also working with a similar problem, and we use the wireless
IWSPY ioctl interface available in the Linux kernel with wireless
options enabled. Note that not all drivers seem to have this interface
so you might need to patch the driver. The way we do it can be
examined from the monitor component used in the most recent release of
the Dynamics - HUT Mobile IP version 0.5, released today. See
http://www.cs.hut.fi/Research/Dynamics for more.

As we examine the access points to find the "best" FA, we can do to
find a "good" next hop in a Manet, or to detect that the current one
for a given destination is broken. The monitor as in the published
form is good for downcall type of interaction, but doing upcalls based
on the signals could also be done (need those patches we try to avoid,
at least with our Mobile IPv4 for the recent Linux kernels). What
wireless link-level info is available, see /proc/net/wireless in Linux.

Basically, the driver maintains a list of signal strengths for given
addresses and we can do decisions based on these. However, the actual
signal figures (we have compared Lucent and Nokia cards) seem not to
behave similarly and we can't passively get a sample at any moment of
time (depends on when the listened station transmits) so the policy by
which we make routing decisions must be carefully designed.

I might also mention that in addition to integrating the mobility
protocols to the link layer we are also in the process of integrating
MM layers together, see the slides of the Manet / Mobile IP issues from
the Oslo IETF45, at http://www.cs.hut.fi/Research/Mart/pap/ietf45/.

About the MM - link level interaction of our work, we have a M.Sc.
work underway.

In what environment (OS, platform) are you developing the WLAN-aware
AODV?

Regards,

--jari

Jari Malinen (http://www.cs.hut.fi/~jtm)
Researcher, HUT/CS Lab. Tel. +358 9 451 4774, fax +358 9 451 5351.

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From: Kevin Purser <[email-masked]>
Date: Fri, 06 Aug 1999 11:03:27 +0200

Samir & Jari,

Thanks for the replies.  Sorry I forgot to mention I'm running AODV on a
number of x86 laptops and linux 2.0.36.