A Progressive Download Method Using Multiple TCP Flows on Multiple Paths

Many high performance network links including wireless ones have become available concurrently to access the Internet nowadays. TCP cannot fully utilize the bandwidth of such network link with high latency and high packet loss rate, so the quality of video playback services using progressive download method sometimes deteriorates on such cases. To cope with the problem, some researches have proposed file delivery methods using either one TCP flow on each of multiple paths or multiple TCP flows on one path. However, a promising method which combines these two has not been studied yet. In this paper, we have proposed a progressive download method using multiple concurrent TCP flows on each of multiple paths. In our proposal, some formulae have been proposed to statically estimate the required number of TCP flows according to the network condition on each path at the commencement of a progressive download process. In addition, a block assignment method, which consists of imposing some offset on the block number assigned to the slower path and requesting the block duplicately which has already been requested but prevents the progressive download process from smoothly replaying, is devised to alleviate the influence of out-oforder block arrivals. Our proposal has been confirmed to yield enough high performance to replay video files with some specified playback rate whenever the parameters including bandwidth, delay, and packet loss rate of multiple network paths are given in the range we assume.