Optimal Cache Partitioning in IPTV Network

Lev Sofman, Bill Krogfoss and Anshul Agrawal

11th Communications and Networking Simulation Symposium (CNS 2008)
Ottawa, Canada, April 14-17 2008

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Summary

In an IPTV network, Video on Demand (VoD) and other video services generate large amount of unicast traffic from Video Head Office (VHO) to subscribers and, therefore, require additional BW/equipment resource in the network. To reduce this traffic (and overall network cost), part of video content (most popular titles) may be stored in caches closer to subscribers (e.g., in DSLAM, Central Offices – CO, or in Intermediate Offices – IO). Different video services (e.g. VoD, NPVR, FCC, etc) have different cache effectiveness (or hit rates) and different size of titles. The problem being addressed is: how can a limited resource – cache memory – be partitioned between different services in order to increase the overall cost effectiveness of caching. The problem of optimal partitioning of cache memory between several unicast video services is a constraint optimization problem similar to the “knapsack problem”, and may be solved by, e.g. method of linear integer programming. Depending on the number of variables, finding a solution may take significant computational time. Basic idea of our solution is to use a special metric – “cacheability” (Cab) to speed-up the process of finding the optimal solution. Cab takes into account cache effectiveness, total traffic and size of one title per service. Our method uses Cab and simple iterative process to find the optimal number of cached titles (for each service) that will maximize overall cache hit rate subject to the constraints of cache memory and throughput limitations.

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