Multipath Overlay Data Transfer

For applications involving data transmission from multiple sources, an important problem is: when the sources use multiple paths, how to maximize the aggregate sending rate of the sources using application-layer techniques via TCP? We solve this problem in the context of an overlay network by allowing a source to send data over k (k ≥ 1) overlay paths to its destination. Our goal is to select the overlay paths for each source and control the sending rate on each path via TCP to maximize the aggregate sending rate of the sources. We prove that optimal path selection is NP-hard and develop two practical applicationlevel multipath rate controllers that use TCP. Our performance evaluation demonstrate that very simple path-selection and ratecontrol algorithms perform reasonably well in a wide range of settings. Furthermore, a small number of overlay paths for a source and a small amount of extra bandwidth in the network are sufficient to realize most of the performance gains.