Subnet Relay - a mobile wireless ad-hoc network

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Subnet relay (SNR) is a realisation of a mobile narrowband ad-hoc network produced by Rockwell Collins Government Systems Canada. The product is mainly developed for maritime users providing Internet protocol connectivity between vessels. It may be used by both the air force and the army to create an interconnected low mobility network. An SNR node controller can utilise existing HF, VHF or UHF narrowband radio equipment, existing link encryption devices as well as modems resulting in relatively low deployment costs. Applications such as e-mail utilising XOmail and chat over Netmeeting have been successfully tested at FFI in laboratory environments. The maximum UDP throughput obtained in a two node network was about 60 kbit/s when utilising a 76.8 kbit/s modem over a 25 kHz UHF channel. For a degraded radio link introducing packet errors, the TCP performance enhancing proxy significantly improved the throughput. FFI follows the standardisation attempts of SNR in NATO AHWG VUHF. The lacking support of IPv6, as well as the fact that Rockwell Collins is not willing to publish the TCP performance enhancing proxy, might require substantial additional effort before a STANAG may be accepted. In addition there are a number of minor issues, such as definition of quality of service classes and the ability to handle merging and separation of networks that require further work. FK-KKIS and NDLO plan to test SNR in an operation scenario, possibly including interoperability tests with the Dutch Navy. FFI will continue the work on characterisation of SNR networks with a larger number of nodes and further investigate the link encryption issues encountered in the current trials.
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