A study on TCP error recovery interaction with random access satellite schemes

Random Access (RA) techniques have been included in the novel DVB-RCS2 standard due to an expected efficiency in addressing SCADA and M2M traffic. Such traffic relies on intermittent sources sending short messages on a periodic time scale. Efficiency is usually assessed in terms of layer-2 packet loss rate without taking into account indirect effects on upper layer protocols. In particular, TCP assumes packet losses as a congestion indication triggering actions aimed to reduce actual transmission rate. As a consequence, TCP over RA can be impaired by some cross-effects, which deteriorate the performance as experienced by the applications, in terms of Round Trip Time (RTT) and overall throughput. The scope of this paper is to analyze such dynamics, by applying a top-down approach, which includes TCP parameters tuning in the scenario configuration. To this aim, an NS2 module has been developed to simulate different flavors of random access techniques for GEO satellite channels integrated with sensor data sources, which produce intermittent messages and send them over TCP connections. Achieved results provide a first set of considerations on the best protocol stack configuration according to TCP traffic load.