关键词: 树型, 代理, 流媒体, 复本放置, 流行度

Abstract:

According to the routing mechanism in tree networks and the distribution characteristics of streaming media accesses,this paper proposes a tree-proxies transparent service model and discusses the problem of the replica placement for streaming media system based on the model. Then,by analyzing the limitation of the commonly-used prefix placement algorithm on tree-proxies model,a non-fixed-length discontinuous placement strategy and two greedy algorithms,namely HGPA ( Hierarchical Greedy Placement Algorithm) and GGPA ( Global Greedy Placement Algorithm) ,are put forward. HGPA places replica level by level from the bottom up in tree proxies,while GGPA performs a greedy placement per segment in the whole tree. Simulation results show that ( 1) both HGPA and GGPA effectively reduce the server load and the cost of network access and are of better performance than the prefix placement algorithm; ( 2) GGPA has a slightly better performance but costs more time than HGPA; and ( 3) comprehensively speaking,HGPA is an ideal replication solution for tree proxies.

Key words: tree topology, proxy, steaming media, replica placement, popularity