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Abstract-In the present paper, ImTCP-bg, a new background TCP data transfer mechanism that uses an inline network measurement technique, is proposed. ImTCP-bg sets the upper limit of the congestion window size of the sender TCP based on the results of the inline network measurement, which measures the available bandwidth of the network path between the sender and receiver hosts. ImTCP-bg can provide background data transfer without affecting the foreground traffic, whereas previous methods cannot avoid network congestion essentially. ImTCP-bg also employs an enhanced RTT-based mechanism so that ImTCP-bg can detect and resolve network congestion, even when reliable measurement results cannot be obtained. The performance of ImTCP-bg is investigated through simulation experiments, and the effectiveness of ImTCP-bg in terms of the degree of interference with foreground traffic and the link bandwidth utilization is also investigated.

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Recently TCP is often used for video streaming applications. Since TCP congestion control is designed to be responsible for varying network conditions, its sending rate adaptation results in throughput fluctuations and leads to poor video quality. To address the problem, a FEC scheme is useful. Since lost packets can be recovered by redundant packets and are concealed from TCP, TCP can maintain higher throughput. To effectively utilize the FEC scheme, the redundancy level has to be appropriately determined so that redundant packets do not waste network bandwidth. Although many dynamic FEC mechanisms are proposed, these mechanisms are not appropriate for TCP video streaming because they do not try to satisfy the required rate. In this paper, we propose a new adaptive FEC scheme called TCP-AFEC that optimizes extra bandwidth usage for the redundancy level. Simulation evaluations show that the proposed mechanism performs better than previous FEC control approaches in various network conditions.