DTN and AX.25

Almost 12 months ago Darren, G0HWW sent this post to the linux-hams mailing list. We exchanged some emails discussing how Delay Tolerant Networks (DTNs) could be used for Emergency Communications (being a classic store and forward network). In a DTN network, each sub-net or point-to-point link can operate over whatever stack is available, in this case it is AX25. In August Darren became aware of some work done in Helsinki University of Technology (under Joerg Ott) specifically a paper entitled Opportunistic Email Distribution and Access in Challenged Heterogeneous Environments. Joerg forwarded Darren their DTN Mail Proxy and we started experimenting with it.

Last weekend, we went a step further. Darren sent me on patches to the DTN2 reference implementation that implement an AX25 Convergence Layer. As I had a working 9600 baud AX25 connection we were eager to test it. After some patching, head scratching and recompiling we were able to successfully pass email from my Laptop over AX25 (439.850MHz) to my Linux server, then over the Internet to Darren’s server and on to his mailbox. All using the DTN bundling protocols. Very cool!

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