Integrated Satellite Networking
Current and previous projects in this area include
GEOCAST and
ICEBERGS.
Multicast IP applications over satellite provide the potential to deliver services effectively at a large scale (in terms of both numbers of users and their geographic spread). We have considered the behaviour of reliable multicast protocols over satellites, looking in particular at one protocol, PGM (Pragmatic General Multicast), which has recently become a experimental Internet RFC standard (RFC3208). We have developed two separate analytical models: the first describes the IP datagram loss rate over a satellite ATM link; the second describes the multicast protocol error performance for each of PGM's three different error correction mechanisms and quantifies the forward and reverse link traffic volumes for file transfer using each mechanism. These models were confirmed by simulation using the OPNET event-driven simulation package. We have developed a novel algorithm for traffic minimisation, showing how to optimise the traffic by varying the application packet size.
After almost half a century since the launch of first artificial satellite, satellites are an integral part of modern communication systems. The space environment provides a whole new spectrum of challenges to communications and networking, and the need to understand the impact of satellite networks on Internet applications and services is essential. As an initial part of this research, a testbed has been constructed to enable the evaluation of the effect of satellite in a multicast multiparty videoconference environment. In addition, a Satellite IP Network Emulator has been developed to study satellite network conditions in a reproducible and controlled manner, emulating satellite propagation delays and errors. These two parameters are the most prominent characteristics of satellite links that are different from terrestrial networks. The testbed and emulator will be used as a foundation for devising new algorithms to achieve QoS in a multicast satellite environment, and thus contribute to the next generation Internet.
