Resequencing Considerations in Parallel Downloads

Several recent studies have proposed methods to accelerate the receipt of a file by downloading its parts from different servers in parallel. This paper formulates models for an approach based on receiving only one copy of each of the data packets in a file, while different packets may be obtained from different sources. This approach guarantees faster downloads with lower network use. However, out-of-order arrivals at the receiving side are unavoidable. We present methods to keep out-of-order low to insure more regulated flow of packets to the application. Recent papers indicate that out-of-order arrivals have many unfavorable consequences. A good indicator to the severeness of out-of-order arrival is the resequencing-buffer occupancy. The paper focuses on the analysis of the resequencing-buffer occupancy distribution and on the analysis of the methods used to reduce the occupancy of the buffer.