Subject: Re: DSR - Problem with ARP

From: Aaditeshwar Seth <[email-masked]>
Date: Fri, 13 Jul 2001 15:03:52 +0800 (SGT)

Hello Sir,

How I wish that I'd known that such a paper already existed! :-) Actually,
I started working on similar lines and came up with the same problems and
solved them in similar ways... I would have saved much effort had I
written to you previously!

Anyway, there are a number of things that I feel can become important when
such a scheme is actually implemented:

- Carrying the neighbor-list with each HELLO message can be quite an
overhead. HELLOs are simple braodcasts, and the larger these broadcast
packets are - greater is the chance of them colliding with other
RTS/CTS/ACK messages: this can significantly effect the MAC performance,
especially with more crowded networks.

- For tunneling the packets from the sink to the source, route-discoveries
will be needed. These could bring up a significant overhead in cases of
high mobility.

However, I think that such a scheme could very well be implemented to
take care of a multi-hop ARP.

Furthermore, if we develop this scheme particular to a set of adhoc-
routing protocols, then we can gain much in terms of avoiding the
HELLO broadcast overhead. For example, in on-demand protocols like AODV
and DSR, the nodes will not be broadcasting their routing information.
In this case, instead of sending the large neighbor-list with each
HELLO packet, the list can be sent only when it is needed to be sent.
Essentially, everything becomes on-demand - even the link awareness
information!!
I know that I'm being a bit too abstract on this, but I am doing just the
very thing in a protocol that I am developing as part of my internship
at KRDL. KRDL has heavy IPR laws, but I think that as soon as we can get
a clearance on this, I can tell more about the basics of the protocol.

Another optimization is to allow the link-layer and the routing-layer
to share their route-tables. Both the parts can gain much in this
manner. Infact, sticking to the layered model doesn't appear to be a
good idea anymore.

Btw: In the real-world scenario, is the existence of unidirectional links
so frequent that it needs so much of effort to be put in? If it is, then
please do send in some ideas on modelling unidirectional links. Also, if
the problem appears to be interesting, then any takers for doing
something on route-table sharing and multi-hop ARPing... do write in...

Thanks,
Aaditeshwar.

On Wed, 11 Jul 2001, Sanket Nesargi wrote:

> Hi,
> 	I am attaching herewith the paper you had requested, "A Tunneling
> Approach to Routing with Unidirectional Links in Ad Hoc Networks",
> presented at ICCCN 2000.
> 	Any feedback from you would be really appreciated.
> 	Thanks,
> 	
> 	- Sanket
> 
> ---------------------------------------------------------------------
> 	Standing on a hill in my mountain of dreams,
> 	telling myself its not as hard as it seems
> 						- Led Zeppelin
> 
> Sanket S. Nesargi
> Distributed Systems Lab
> University of Texas at Dallas,
> Richardson TX 75082				<[email-masked]>
> ---------------------------------------------------------------------
>