DieselNET
How many types of computer networks do you know? There is the most common TCP/IP networking, across copper, fiber or wireless (very likely that is what you are using to read this page). IPv6 is the new kid on the block, and some may remember the old stuff, like Tokenring and IPX, and when all else fails, good, old sneakernet is never down! Now there is also DieselNET. On DieselNET, data take the bus – no not the SCSI bus! The BUS, as in public transportation! No joke! In this implementation of a packet-switched network protocol, the data are ferried across town by hitching a ride on the buses of the Amherst PVTA transportation system.
The University of Massachusetts at Amherst Diverse Outdoor Mobile Environment (DOME) Project is researching technology for disruption tolerant networking (DTN) systems (via NetworkWorld).
DieselNet currently consists of 40 buses each with a Diesel Brick, which is based on a HaCom Open Brick computer (P6-compatible 577Mhz CPU, 256MB RAM, 40GB hard drive, Linux OS). The brick is connected to three radios: an 802.11b Access Point (AP) to provide DHCP access to passengers and passersby, a second USB-based 802.11b interface that constantly scans the surrounding area for DHCP offers and other buses, and a longer-range MaxStream XTend 900MHz radio to connect to our throwboxes. Additionally, a GPS device records times and locations. Our custom software allows us to push out application updates, take mobility, AP-to-bus connectivity, and bus-to-bus throughput traces.
UMass Amherst – DOME website, Nov. 23, 2006
The idea here is to create systems that can route messages without knowing exactly where the message is going, because most nodes are only up for limited amounts of time (an average of 20 percent on DieselNET). So when two nodes are in range, they query each other for the other nodes they are likely to encounter along the route, and they pass messages along based on that information.
Why bother? Well, for one, DARPA has money for this kind of research. And I am sure the military has all kinds of ideas for implementations. Imagine a couple of dozen/hundred/thousand nodes (people who carry a wireless computer or robot/rover devices). If these nodes were moving about in more or less predictable ways, and not scattered too widely, a DTN could relay messages within that group within seconds from one end to another and failures of individual nodes have very little impact on the system as a whole. You can see, perhaps, why the military might be interested in this idea. But I think there might be also very useful civilian uses, like in disaster recovery, exploration of extreme environments (space, under water) and maybe in regular communications.
BTW: if these folks have their way, DieselNET should really be BiodieselNET!