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Proposition of a mechanism to divide a MANET network into - - PowerPoint PPT Presentation
Proposition of a mechanism to divide a MANET network into - - PowerPoint PPT Presentation
2nd OLSR Interop / Workshop Proposition of a mechanism to divide a MANET network into subnetworks of given size What are we talking about? Definition ... A subnet is simply defined by the adding of a subnet identifier parameter to
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So... For OLSR, that means...
(first in a static situation)
5 15 25 35 45 55 65 75 85 100 110 0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00% 100.00%
delivery rate
10 30 50 70 90 110 130 150 170 190
Number of nodes Delivery rate
30 < Ideal size < 55
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By the way... What for???
(yes yes, I assure that we care ;) )
Developing a routing protocol for example
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Of course... The other difficulty is in building subnet scale topology ...
But that is an other story...
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To switch or not to switch that is the (only) question...
A node can change its subnet identifier (ie
its subnet) when it receive a Hello message from an other subnet's node. (Connexity partially solved)
Therefore the only matter is to decide if a
network switches its subnet.
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“Pressure and Transfer” or “how to manage human (node) resources”
Pressure is the “desire” of a node to leave
its subnet. Pressure is sent with hellos.
When a node receives a “foreign” hello it
can compare the pressure and determine a probability to leave its subnetwork given by a “transfer” function.
There are two function to be determined : the pressure's
- ne and the transfer's one
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Working under pressure...
(make us want to leave ;) , nodes too)
The process makes the whole subnet to
“seek” a low pressure situation. Therefore the pressure must be the lowest for the de- sired subnet size.
On the contrary, too small or too large net-
works are to be forbidden therefore their pressure is higher.
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But... What do we want for subnets exactly?
Minimal size (above which the subnet
should be “diluted”)
Ideal size Excessive size (would lead to inefficiency of
OLSR)
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Booting (subnet's genesis)
Every node is its own subnet Unique subnetwork identifier
(name + iterator?)
Non null transfer probability for equal pres-
sures
Same process for subnet collapse (every
node becomes its own subnet)
“And OLSR said, Let there be subnet : and there was subnet. And OLSR saw the subnet, that it was good”
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One stable balanced situation...
The goal is that their is only one stable bal-
anced situation (the ideal case of course).
BAD GOOD OR
“a tribute to monogamy” ;)...
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Which leads to
The slope difference has been exaggerated Flat pressure for large subnet
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“Too much pressure here... I quit!”
An anonymous node before being transfered
By the way... And if we were... lazy? Elementary constraint : “leave for lower
pressure” or “nodes aren't masochists”...
(To be applied in real life too ;) )
Letting time for “cooldown”
Transfer function :
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Things are simpler than they seem...
(bless be commutativity...) Network size doesn't cheat the results(A*N=N*A)
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...But not trivial...
Reduce parasite changes Make better switching choices Trying to speed up the convergence
Half life concerns (and Freeman won't help...)
...But not trivial... ...But not trivial...
With trivial tranfer function ( P(change) = constant * ΔP ) Subnet of a good size but... After 100 seconds of simulation : A half life of only 25 seconds (in other words, around 200 changes in 10 seconds)
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Work on (ΔP)² (makes pressure differences
more efficient)
Divide by subnetwork size (in fact it did
cheat a bit...)
Some minor upgrades
Some enhancements : And Finally :
P(change)= constant * (ΔP)² / (subnetwork size) leads to a 400 seconds half life
(Half) Live longer...
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