Testing MDP in a simulated space channel environment

The performance of the Multicast Dissemination Protocol (MDP) in a simulated satellite channel is investigated. The environment that is modeled is that to be expected in a small satellite communications environment including channel errors and link interruptions. The satellite link is simulated with a channel environment simulator. The performance of MDP is compared with file transfer protocol (ftp) acting as a standard basis. In these experiments, we find that MDP does not perform as well as ftp in the high quality channel, although the performance difference is small. MDP does perform better than ftp in low-quality channels. MDP is also able to resume data transmissions when a link outage occurs. MDP is seen as being a viable option for use in small satellite communications systems. INTRODUCTION The use of Internet-type protocols for space communications over bent-pipe links has been well studied and the expected performance well characterized. Much of the research has examined the performance of the Transmission Control Protocol (TCP) in space from observations of simulation and experimental testbed results. See, for example, [1], [2], and [3]. The purpose of these studies was to identify a better TCP variant for use in long-delay networks, such as those found in the satellite environment and to investigate the effect of latency on aggregated network utilization. One next logical evolution in the process is to consider the satellite to be another node on the Internet. Research on this subject has been conducted at government, contractor, and university facilities for several years now; see, for example, [4], [5], and [6], and 1 This effort was funded under grants NAG5-7520 and NAG5-9323 from the National Aeronautics and Space Administration.