uucp for sneakernet (was Re: Emulating the School...]

[david at lang.hm]

On Wed, 5 Mar 2008, Adrian Chadd wrote:

> On Tue, Mar 04, 2008, david at lang.hm wrote:
>
>> the good news is that you can simulate things by useing UDP broadcast
>> packets as your transport layer.
>
> Well yes, I did usenet/proxy object stuff over UDP.
>
>> don't get fixated on the idea of using satellites, as a means for
>> publishing updates a high-powered AM or SSB station can blanket a large
>> area, and the efficiancy gained by only transmitting things a couple times
>> (including error correction to deal with missed packets) instead of once
>> to each destination can counter the drawback of a low bit rate.
>
> Terrestrial RF would certainly be interesting to trial, but I don't have
> any equipment here to toy around with and I don't have a radio licence
> to roll my own.
>
> Still, I'd be interested in helping out if anyone is interested.

you should be able to test the concepts using wifi with UDP broadcasts. 
once you have the concepts down and are just needing to nail down the 
radio details things get pretty easy. the receiving equipment can be as 
simple as a radio with headphone jack to plug into a sound card (not 
ideal, but a good first approximation), and there are enough Ham Operators 
around that we can setup real-world transmit tests (and hams have been 
doing packet radio broadcasts for years, 1200 bps on FM is trivial, 9600 
not too hard, on SSB/AM you are probably talking 300-1200 bps with cheap 
equipment (better equipment can do 9600, but that's fairly pricy, at that 
point satellite receivers are probably a good option)

get the basic protocol worked out and then we can dive into the transport 
details.

you may want to look at including an option that once a file gets past x% 
complete for more then Y time, the receiver will take active steps to fill 
in the gaps (if a school server has most of the update it can request the 
last little bit over a landline rather then waiting for the gap to be 
filled in in a later broadcast)

David Lang