Hi all,
The Delay Tolerant Networks Research Group (dtnrg.org) of the IETF
have developed an overlay network architecture and protocol (the
Bundling Protocol) primarily for use in joining the Interplanetary
Network with terrestrial nodes, using persistent incremental store
and forward techniques. They also have developed the Licklider
Transmission protocol (LTP) for delay tolerant operation over point-
to-point links. The concept has moved on to include DARPA programs
and is extended for disruption tolerance too. The DTN2 reference
implementation of the bundling protocol is open source and has moved
(mostly) to an Apache 2 licence.
Anyway, I've just implemented a convergence layer adapter for AX.25
SEQ_PACKET sockets which carries the bundling protocol. It's not
currently in CVS, as I'm not familiar enough with autotools to sort
it the configure scripts yet, and its only been running since Sunday.
The code is pretty much a direct port of the existing TCP convergence
layer and has been tested through a pk232 in KISS mode with a
loopback cable. It may not be perfect yet but it seems to work well
enough. I've not yet provided support for digipeating, and the link
configurations are a little iffy.
The DTN2 RI code works happily on embedded Linux too, such as my
NSLU2 (Debian Etch) and the GUMSTIX, although I've not looked at AX.
25 support in those yet, and on Macs. With DTN nodes scattered
around, it is possible to create an overlay network encompassing
internet connectivity and extending over AX.25 links (with suitable
Linux gateway nodes). Work is being done on probabilistic routing
and discovery mechanisms. It offers TCP, UDP, and Bluetooth CLs
already.
I'm a little isolated here in terms of AX.25 connectivity (but with
some APRS connectivity and the odd packet through the ISS) so I've
not tested it on air. I wondered if someone else might be interested
enough to have a go at building and firing up the DTN2 implementation
and taking a look at my (our) code ;-)
Darren, G0HWW
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