Comparison of Caching Strategies in Modern Cellular Backhaul Networks

Recent popularity of smartphones drives rapid growth in the de-mand for cellular network bandwidth. Unfortunately, due to the centralized architecture of cellular networks, increasing the physical backhaul bandwidth is challenging. While content caching in cel-lular networks could be beneficial, little is known about the traffic characteristics to devise a highly-effective caching strategy. In this work, we provide insight into flow and content-level char-acteristics of modern 3G traffic at a large cellular ISP in South Korea. We first develop a scalable deep flow inspection (DFI) system that can manage hundreds of thousands of concurrent TCP flows on a commodity multicore server. Our DFI system collects various HTTP/TCP-level statistics and produces logs for analyzing the ef-fectiveness of conventional Web caching, prefix-based Web caching, and TCP-level redundancy elimination (RE) without a single packet drop at a 10 Gbps link. Our week-long measurements of over 370 TBs of the 3G traffic reveal that standard Web caching can reduce download bandwidth consumption up to 27.1 % while simple TCP-level RE can save the bandwidth consumption up to 42.0 % with a cache of 512 GB of RAM. We also find that applying TCP-level RE on the largest 9.4 % flows eliminates 68.4 % of the total redundancy. Most of the redundancy (52.1%∼58.9%) comes from serving the same HTTP objects while the contribution by aliased URLs is up t