基于内容流行度差异性的CDN-P2P融合分发网络缓存替换机制研究

Content popularity difference-aware cache eviction scheme for CDN-P2P hybrid networks

现有的CDN-P2P缓存替换机制没有关注内容文件中各片段的个体流行度差异性,而无法提高预缓存内容片段的访问命中率。鉴于此,提出了基于流行度差异性的缓存替换机制Diff-Attribute。同时考虑了内容文件的整体流行度和文件中各个片段的个体流行度。此外,基于分布熵,定义了一种内容流行度均衡性度量方法:若流行度均衡,就提前缓存各文件的前缀片段;否则提前缓存热门文件或其中最热门的内容片段。仿真结果表明:在缓存命中率和字节命中率方面,Diff-Attribute机制分别高出LFU、LRU等传统机制约6%和8%;在访问延迟启动率和传输成本消耗率方面,Diff-Attribute机制则降低了约13%和7%。

In CDN-P2 P hybrid network, it is important for the cache eviction schemes to improve the delivery efficiency of content. However, most of them only consider the holistic popularity of content file, and neglect the difference between the individual popularities of segments within a content file. Hence, it was difficult to improve the hit rate of pre-cached content segments, and to reduce the user access delay. Hence based on the difference between the attributes of content popularity, a new cache eviction scheme(i.e., Diff-Attribute) was proposed. Bewildered the holistic popularity of a content file, it also considered the individual popularity of its segment. More importantly, based on the concept of entropy, A method to measure the popularity difference between content files or segments was put forward. If the popularities of the segments within a content file are equalizing, its prefix segment would be pre-cached. Otherwise, the requested segments or files directly based on its popularity would be cached. Compared with traditional schemes(e.g., LFU, LRU, MRU,FIFO), the simulation results show that Diff-Attribute can improve the cache hit rate and the byte hit rate by at least 6%, 8% respectively, and can reduce the access startup delay rate and the transmission cost rate by at least 13%, 7% respectively.