Cache Replacement Policy Based on Server Distance

The transmission bandwidth consumed by delivering rich content is enormous, so it is urgent for Internet service providers to design an efficient delivery system that minimizes the amount of network resources consumed, i.e., minimizing the hop length of delivery flows. Content delivery networks are widely used to reduce the flow hop length and the response time when obtaining content items. To improve the cache efficiency, various methods of replacing caches have been proposed, with the target of improving the cache hit ratio. However, although the effect of delivering content items from caches depends on the distance from the origin server to the users, these methods do not consider the origin server distance. We propose here a cache-replacement policy based on the hop distance to the origin servers. We divide the storage capacity of cache severs into multiple virtual caches and manage content items separately based on the hop distance to origin servers. We also propose an optimal method for designing the capacities of virtual caches that maximizes the total expected reduction of flow hop length. Through numerical evaluation, we show that the proposed method can increase the average expected reduction of flow hop length by about 20% to 80% compared with normal LRU (least recently used).