Scalability of manets (was: Re: [OLSR-users] Question about OLSR

[Jens Nachtigall]

Dear all,

>> your
> > bandwidth will be saturated by control messages alone.
>
> Not only that, but you must remember that standard WLAN today only
> have one antenna, so it cannot send and receive at the same time. 

Actually it is even worse :-(. Afaik the biggest scalability problem is 
not the one of increased control messages, or interference as outlined 
above. But the biggest problem is, that if the net increases my node 
will have to forward more and more packets on behalf of other nodes. 
Therefore, my node can hardly issue packets on his own. 

If the traffic does not remain primarily local when the manet grows, 
then the throughput available for each node will grow towards 0. 
I don't want to go into detail here, but there is a very nice paper on
http://www.pdos.lcs.mit.edu/papers/grid:mobicom01/paper.ps.gz
(8 pages, not too much brainfuck). The paper sums scalability issues up 
pretty nicely.

So I would argue, that Bruno's throughput values are very good taken the 
interference problem. But I'd say that the biggest problem of manets 
did not occur yet in Berlin, because most nodes are routers who don't 
issue packets on there own, but do only forwarding. So these values are 
pretty much because, there is not much congestion/concurrent traffic so 
far.

@Bruno: Nice topology screenshot :-) I guess it was you who added the LQ 
feature. Very Nice. In case, you are still down with the topology 
plugin, I'd very much like to see some integration of the MIDs. I often 
find the routing table quite misleading, because there seem to be quite 
a few MIDs around. (maybe just having several IPs in one box would do). 
Anyway, I also like your view-topology script, and wonder if it could 
be changed to run only once, so that I could use it as a cron job. This 
way I could put the topol image on my web site. Maybe even a cgi option 
would be nice (I don't speak perl). Then you could have a look at the 
net from my point of view ;-)
 Also, if you feel like it you could do a "netperf -p 12865 -H 
104.193.1.5". the x.x.x.5 is my IP and since we are both on the very 
west/east of the net, a test might be interesting. though, i don't know 
if the loops that currently in the net might harm this.
Just my wishlist after xmas ;-) But I guess you welcome some feedback, 
and you know, just as time permits and you feel like it.

good night,
Jens

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