The space communication environment and mobile and wireless communication environments show many similarities when observed from the perspective of a transport protocol. Both types of environments exhibit loss caused by data conuption and link outage, in addition to congestion-related loss. The constraints imposed by the two environments are also similar -power, weight, and physical volume of equipment are scarce resources. Finally, it is not uncommon for communication channel data rates to be severely limited and highly asymmetric. We are working on solutions to these types of problems for space communication environments, and we believe that these solutions may be applicable to the mobile and wireless community. As part of our work, we have defined and implemented the Space Communications Protocol StandardsTransport Protocol (SCPS-TP), a set of extensions to TCP that address the problems that we have identified. The results of our performance tests, both in the laboratory and on actual satellites, indicate that the SCPS-TP extensions yield significant improvements in throughput over unmodified TCP on errorprone links. Additionally, the SCPS modifications significantly improve performance over links with highly asymmetric data rates.

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