[Freedombox-discuss] Freedombox Mesh Network Simulator
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On 06/20/2012 02:13 PM, John Gilmore wrote:
> Internet while the problem is happening, to debug it. Many, many
> OLPC mesh problems occurred in the field which could not be
> replicated in the lab, which made them 10x or 100x harder to fix.
> This meant that buggy mesh network firmware and software didn't
> improve at the usual rate (of the rest of their software).
We were able to replicate some of the problems they had at HacDC (we
have a stack of OLPCs on the shelf that we use as test systems sometimes).
> The result was that despite a lot of work addressing bugs and
> performance in the mesh firmware, they never got their automatic
> mesh network working with more than a handful of XO laptops. If
> you put 30 laptops in a classroom, they would burn up 100% of the
> radio bandwidth (and chew up their batteries) merely with overhead
> packets ("Hi, i'm
Yep. 30 nodes in a single classroom is catastrophically too many.
One or two work are enough. I don't think they ever tried that
particular set up in the lab before shipping.
> There ARE some mesh networks that I hear are working on a larger
> scale, such as B.A.T.M.A.N. I suspect that the large scale meshes
> are in largely static networks that are tuned by humans to work
> well (just
Some are, some aren't. Battlemesh is, as I recall.
> it's not automatic). I do not know if other meshes support
> multicast (or other portable ways for high level software to find
> what nodes are on the network), nor whether they work in a network
> of mobile nodes
Byzantium Linux does; we're testing it in the field right now.
> with limited battery life. All I can report on is the one project
> I
Mobiles as mesh nodes? It's a dicey proposition due to power
consumption. Mobiles as mesh clients are more workable.
> available bandwidth. Every connection you move off wireless onto
> a wire makes more radio bandwidth available for the folks who
> truly can't run a wire.
This is true. Also, if the network topology involves patches of
meshes connected with second radios (like USB wi-fi keys) it frees up
bandwidth for the clients.
> PS: If you think a mesh protocol shouldn't use even a
> megabit/second of continuous overhead, please design and build one
> that doesn't, and that scales up and keeps working. It's harder
> than it looks.
Babel doesn't. I think our biggest mesh pushed a couple of kilobits
per second of overhead.
- --
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