Caching in video CDNs: Building strong lines of defense

Planet-scale video Content Delivery Networks (CDNs) deliver a significant fraction of the entire Internet traffic. Effective caching at the edge is vital for the feasibility of these CDNs, which can otherwise incur significant monetary costs and resource overloads in the Internet. We analyze the challenges and requirements for video caching on these CDNs which cannot be addressed by standard solutions. We develop multiple algorithms for caching in these CDNs: (i) An LRU-based baseline solution to address the requirements, (ii) an intelligent ingress-efficient algorithm, (iii) an offline cache aware of future requests (greedy) to estimate the maximum caching efficiency we can expect from any online algorithm, and (iv) an optimal offline cache (for limited scales). We use anonymized actual data from a large-scale, global CDN to evaluate the algorithms and draw conclusions on their suitability for different settings.