The invention relates to an 
overlay network layered 
multicast optimal 
resource allocation method for a scalable video 
stream, and provides a new measurement standard for the 
multicast performance, namely layer extensity which is used for measuring end-to-end time 
delay of video 
layers during data distribution aiming at layered 
multicast communication of the scalable video 
stream in the 
overlay network. In order to realize the overall minimization of the layer extensity, the method carries out the combined optimization on the 
network code of 
relay nodes, the receiving end driven flow control, and multi-path 
route strategy, and adopts a 
linear programming method to establish a layered multicast resource optimum allocation model for the 
overlay network. On one hand, the method adaptively matches the interlayer dependency of the scalable video code; on the other hand, the method allows a receiving node to decide and regulate the required 
video quality of own accord. In addition, the invention also provides a distributed 
heuristic algorithm which has 
low complexity, approaches the globally optimal solution and is applied to the construction of a scalable video flow distribution network.