HKUST
Large-scale content delivery systems such as the web often deploy multiple caches at different locations to reduce access latency and network traffic. These caches are usually organized in a cascaded fashion where requests not hitting a lower level cache are forwarded to a higher level cache. The performance of cascaded caching depends on how the cache contents are managed, including object placement and replacement strategies. In this talk, we present a general analytical framework for coordinated management of cascaded caches. The object placement problem is formulated as an optimization problem and the optimal locations for caching objects are computed by a dynamic programming algorithm. Based on the framework, we propose a novel caching scheme that incorporates both object placement and replacement strategies. The proposed scheme makes caching decisions for the set of caches lying on the delivery path of a request in a coordinated fashion. In addition to analytical modelling, our study is also accompanied by simulation experiments based on both synthetic workload and real traces collected from web caches. The experiments have been conducted under two different cascaded caching architectures: en-route caching and hierarchical caching. The results show that for both architectures, the proposed scheme significantly outperforms existing schemes that consider either object placement or replacement at individual caches only.