Subject: AODV implementation

From: Kevin Purser <[email-masked]>
Date: Thu, 04 Nov 1999 11:16:53 +0100

Hello all,

As we have received numerous mails recently regarding our
AODV implementation, here's a summary of what we are presently doing,
and the problems we've run into to date.

My responsibility involves incorporating internet access into ad hoc
networks through the use of Mobile IP (for dataflow into the ad hoc net)
and modifications of AODV (for gateway support for the opposite
direction of dataflow).

Additionally, we have attempted to include link-layer feedback to allow
quicker detection of broken links.  We have been using using drivers for
the Lucent WaveLAN 802.11 PCMCIA cards with drivers from both
TriplePoint, Inc. and Andy Neuhaus.  Neither have offered any assistance
in the way of achieving such feedback from their drivers, so this aim
has been postponed.

In order to to use Mobile IP for ad hoc networks, a few modifications
have been made.  First and foremost, since the connection between a
FA and a node within an ad hoc network may traverse multiple hops, we've
moved Mobile IP from the link-layer into the IP layer to allow the
connection to be fulfilled through IP forwarding.  There are a number of
other questions as to how to resolve the differences in MIP and the on
demand behavior of AODV, which are under investigation.  Some examples:

* Should a FA continue broadcasting it's periodic advertisements
throughout the ad hoc network, should they be restricted in some way, or
simply be removed entirely?

* If multiple FAs can be reached by nodes in an ad hoc network, which is
the "best" to use, and how to we acquire this metric?

* If a path to a node's currently registered FA is broken, should it try
to re-establish a path to that FA, or immediately try to discover a new
one?

Regarding the opposite direction of dataflow, supporting multiple
gateways also poses problems:

* If a node requests a route to a destination which may reside on the
internet (or within the ad hoc network using mobility mechanisms), how
should gateways respond to such requests?

* If multiple gateways can be reached by nodes in an ad hoc network,
which is the "best" to use, and how to we acquire this metric (a less
specific version of the problem involving multiple FAs)?

These are all under investigation through simulation, and a canonical
implementation is also underway.  The results of these works will
published during the coming months.

Regards,
Kevin Purser

--
==========================================
Kevin Purser
Switchlab, Ericsson Radio Systems AB
------------------------------------------
Torshamnsgatan 23, Kista
S-164 80 Stockholm, Sweden
------------------------------------------
Phone: +46 (08) 508 78 101
Fax:   +46 (08) 508 78 090
==========================================