[Freedombox-discuss] Freedombox Mesh Network Simulator

The Doctor drwho at virtadpt.net
Fri Jun 22 19:00:25 UTC 2012

Hash: SHA1

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.

- -- 
The Doctor [412/724/301/703] [ZS]

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