SpeedDetect: a simple TCP extension for handling sudden capacity increase
NGI'09 Proceedings of the 5th Euro-NGI conference on Next Generation Internet networks
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We analyse throughput adaptation of high-speed TCP protocols during handovers in an emulation testbed. We use emulation characteristics reflecting current mobile networks and future network specifications as set by the relevant standards. We found that the performance of TCP protocols is satisfactory, except as follows. Traditional loss-based TCP-s like BIC, HighSpeed and Scalable adapt slowly to sudden link capacity increases caused by handovers. FAST TCP adapts much faster, however depending on parameter settings it may under-utilise after a capacity decrease coupled with RTT increase. We also calculate the probability of buffer overflows at handover as the function of the buffer size and transmission parameters at the bottleneck link. This probability turns out to be significant for reasonable scenarios, and we suggest a dynamic buffer re-allocation method to eliminate such buffer overruns in mobile networks.