Subject: RE: [manet] AODV Question

From: DANIEL BYRNE <[email-masked]>
Date: Fri, 14 Nov 2003 14:07:40 -0600

>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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From: "John Mullen" <[email-masked]>
Date: Fri, 14 Nov 2003 13:25:03 -0700

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: [email-masked] [mailto:[email-masked]] On Behalf Of
DANIEL BYRNE
Sent: Friday, November 14, 2003 1:08 PM
To: 'Erik Nordström'
Cc: [email-masked]; [email-masked]
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.  

>(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.

---

From: "Charles E. Perkins" <[email-masked]>
Date: Mon, 17 Nov 2003 07:27:18 -0800

Hello folks,

One or two comments below:

> Yes we did, but everyone here is now saying that AODV doesn't work well

I can believe that the performance would suffer
greatly, depending on the mobility of the intermediate
nodes.  If the nodes didn't move, then I wonder what
would go wrong?

Regarding the idea about replacing land lines,
I guess that any routing protocol would work,
even manual configuration.  To overcome the 
hop limit, you could do encapsulations.

It doesn't seem to be a close match for the
technology provided for use with mobile ad
hoc networks since:
1) the nodes aren't mobile, and
2) the network isn't ad hoc.

Regards,
Charlie P.

---

From: "John Mullen" <[email-masked]>
Date: Mon, 17 Nov 2003 09:07:11 -0700

Hi Charlie,

Well, I can see one application of MANET technology in a situation in
which the nodes do not move.  Consider the Dine' (Navajo) nation which
covers thousands of square miles in the southwestern US.  Connecting the
many isolated communities with wire or fiber does not seem to be an
option.  Furthermore, the Dine' would prefer not to use the ideal places
for antennas because of religious and other reasons.  Every time you dig
a hole on the reservation, you need an archeologist.  Other American
Indian jurisdictions are checkerboarded.  That is, there are parcels of
fee simple land owned by non-members of the Tribe interspersed
throughout the area.  In those cases, right of way is a big problem.

It is not just that putting up telephone poles is a problem, but also
that a common electrical supply is often not available.  That is, any
repeaters would have to be self-powered.

Now, imagine a network of nodes that are powered by batteries, which in
turn, are recharged by solar energy.  Also, assume the net is dense
enough that many nodes can go to standby while the others take the load.
However, as the evening wears on, the active nodes, one by one, will
have to shut down due to low power.  Others could, at any time, have to
shut down due to malfunctions (we a talking of many nodes in a very
hostile environment).  As each does so, one or more inactive nodes wakes
up to take the load.

Such a net would have no mobile nodes, but would require frequent
automatic reconfiguration.  It wouldn't be entirely a MANET, since each
node could know where every other node was, but would require a degree
of automatic reconfiguration that ordinary protocols would not support
due to the frequent changes in the pattern of available nodes.  I would
think that at least part of a MANET protocol would be helpful.  Also, if
such a protocol were to be used, mobile nodes could be more easily
accommodated as they move throughout the communications area.

Just a thought.

John Mullen

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Charles E. Perkins
Sent: Monday, November 17, 2003 8:27 AM
To: DANIEL BYRNE
Cc: 'Erik Nordström'; [email-masked]; [email-masked]
Subject: Re: [manet] AODV Question

Hello folks,

Regards,
Charlie P.