Subject: Re: [manet] Internet-MANET gateways?

From: Manish Karir <[email-masked]>
Date: Thu, 12 Jun 2003 15:18:28 -0400

few problems with that.

- your address-space to number of nodes ratio is really large, so
    ofcourse you will get a good answer.:) but thats okay...lets
    use your example anyways...
- how do to propose we perform collision resolution across even
    100 nodes, everybody broadcasts to everybody multi-hop(across
    100 nodes, remember everyone has to hear everyone else, everyone
    is doing this at network bootup, so everyone is doing this at the
    same time, messages are lost, there are collisions)?.
    say node 10 hears
    somebody else(87) saying it has the same id, now node 10 will
    change its id then re-broadcast, but so will 87, which will also
    rebroadcast there might be another collision so again id is changed
    and again rebroadcast.
    The answer of one round is only valid in some cases. If you try
    enough random seeds, you will hit the scenario where it takes 10
    rounds or maybe even more.  Its only a matter of probability
    of what "state" your network comes up in, there are no gurantees
    that your network will intialize in say 10 seconds, or even
    say 600 seconds.  Forget about the army even commercial devices would
    not want unpredictable properties like that.
- what happens when messages are lost? so does this collision resolution
    need to be performed periodically, just in case the last time it
    failed to detect duplicates due to dropped pkts?
- now lets scale it up, to 200 nodes, then 500 nodes then 1000 nodes,
    it gets harder and harder....bottom line the
    solution does'nt scale to even "small" numbers.

-manish karir

Jon Zeeff wrote:
 >
 > Let's try it with a 24 bit address space, a 10x10 array, and when a
 > collision is detected, you
 > don't throw the whole thing out and start over, you simply pick another
 > address for that
 > single node in the array.
 >
 > Answer: one round
 >

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From: Einar Vollset <[email-masked]>
Date: Fri, 13 Jun 2003 10:24:05 +0100

>    failed to detect duplicates due to dropped pkts?

Use a reliable broadcast protocol.