Delay-tolerant networking tested

A protocol for transmitting data across networks with
intermittently-working nodes has been tested for the first time in one of its
intended environments: space.


The BundleProtocol, which was devised by the Delay Tolerant Networking ResearchGroup, involves storing data packets on a router and
holding them until the next node in the network becomes available
again.


In the test, a ground station in Guildford, England, run by
Surrey Satellite Technology Ltd. (SSTL) downloaded an image taken
by a Disaster Monitoring Constellation satellite passing overhead. The Bundling Protocol was implemented on the SSTL computer receiving the image. The image, South Africa's Cape of Good Hope, was downloaded in fragments during two separate passes. The ground station then sent the image fragments, via Internet, to the NASA Glenn Research
Center, which reassembled the image.


The DMC satellite, one of four low Earth orbiting satellites
SSTL launched for the U.K. to capture images of natural disasters,
was equipped with a Cisco router. SSTL also contributed a file transfer
protocol, called Saratoga,
for transmitting data to the ground station.


The Bundling Protocol could be invaluable in setting up an
Internet Protocol-based data communications network in space that
could be used by satellites, an approach known as Delay Tolerant
Networking (DTN). While IP requires all nodes in a communications
chain to be operational, this protocol can hold packets should one
node be unreachable. In space, a satellite may fall out of
connectivity as it orbits around an obscure side of a planetary
body.


DTN could also be used for more terrestrial duties as well.
Networks on a battlefield or at the site of a natural disaster
could benefit from a protocol more forgiving of lost nodes. The
Defense Department's Advanced Research Projects Agency has fundedwork to further DTN for these uses.


About the Author

Joab Jackson is the senior technology editor for Government Computer News.

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