A Progressive Download Method Based on Timer-Driven Requesting Schemes Using Multiple TCP Flows on Multiple Paths

Due to the widespread use of broadband communication media, it is often the case that the conventional TCP cannot fully utilize such broad bandwidth; hence, many improvements on TCP itself and a lot of accelerating methods which use multiple TCP flows have been proposed. In addition, video hosting services on the Internet as a new medium have become popular, and progressive downloading methods, which download segmented video data while replaying them, are adopted on various sites. The playback quality of progressive download methods has been improved by the existing method which establishes multiple TCP flows on each of multiple paths. However, the existing method assumes that bandwidth, delay, and packet loss rate of each path are known. Therefore, in this paper, a method using the timer-driven requesting scheme which is to be effective even when bandwidth, delay, and packet loss rate are not given. Moreover, it features duplicate requesting scheme to cope with quality deterioration in video playback due to out-of-order block arrivals when conducting progressive download using multiple paths. This paper evaluates the proposed method comparing with the existing method by simulation. As a result, it is found that the proposed method yields high performance enough to keep the video quality higher than or similar to the existing method even though the network condition is not clarified in advance. The proposal can be regarded as an assurance network technology since it can adapt to the current network status and keep the playback rate high.