RE: [manet] AODV Question

["John Mullen" <jomullen@nmsu.edu>]

Hi Daniel,

Your idea has promise, especially in areas where right-of-way is a
problem.  However, it may not be necessary to use a MANET protocol.  If
the relay points are stationary and in a known relationship with one
another, a more conventional routing protocol might work.  In such a
situation, routes could be very stable and the only thing each node
would need to know is whether or not to re-broadcast after receiving a
packet.  That is, the routes could be embodied in routing tables with no
need to imbed them in the packet headers.

Also, there might be lower-cost alternatives.  Where the right-of-way is
established and infrastructure (e.g. poles) exists, fiber is relatively
cheap.  Remember that your 200 nodes will have to be maintained and will
need a source of power.  Also remember that bandwidth is much lower and
signal strength much more variable in a wireless channel than a fiber
one, so your terminals would have to be rather expensive to provide even
a fraction of the capability of a fiber cable.  In addition, a microwave
link could be an option in some parts of the net.  That is, even if you
use wireless links for part of the backbone, you need may not actually
use a MANET protocol and there are liable to be some long hops.

John Mullen

-----Original Message-----
From: manet-admin@ietf.org [mailto:manet-admin@ietf.org] On Behalf Of
DANIEL BYRNE
Sent: Friday, November 14, 2003 1:08 PM
To: 'Erik Nordström'
Cc: manet@ulfius.com; manet@ietf.org
Subject: RE: [manet] AODV Question


>I guess the point is not whether you would like to or not, but rather 
>if it is feasible with 255+ hops. And we did talk about AODV...
Yes we did, but everyone here is now saying that AODV doesn't work well
over 50 or more hops.  

>In the Internet I guess that an average hop count would be 20-30 hops 
>(with max around 60, correct me if I am wrong).

So the Internet has 20-30 max hops right now.  So what.  The internet
backbone is composed of very long expensive cables that someone has to
pay for.  The reason I started this thread was because that I was
considering whether or not a radio multihop network could replace
expensive long haul lines between routers.

The theory is if you could replace long, expensive, fiber optic cable
runs with wireless relay points that could double as routers, then
potentially anyone could own and operate a long haul backbone.
Obviously this is a topic for another thread.  However, to divulge, if
it could be made cheaper to pop down 200 wireless nodes in a chain
configuration rather then lay fiber I believe there could be a large
market for chain topology wireless networks.  In which case I guess AODV
would either have to be modified, replaced with a more capable routing
protocol or something else yet undiscussed.  I'm of course just
theorizing right now.

As far as bandwith is concerned, I know of one current product that
delivers DS3 equivalent bandwidth over 25 miles.  That is enough
bandiwth to make 768 residential ADSL customers pretty happy.  255 of
these in a row would give you a 6375 mile long broadband pipe, all
without wires.  That's long enough to extend from Juneau Alaska to Tampa
Bay Forida.  The extra hops would be used to service individual
communities, or various corporate offices along the way.  All with
leasing a single DS3 line from  Ma Bell.

The only major stumbilng block I see in such a configuration is node
latency.  However, I don't think the AdHoc routing protocols should
concern themselves with the speed of the devices that they run
themselves on.  We'd let the hardware designers figure that one out
later.

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