SoftCell: Taking Control of Cellular Core Networks

Existing cellular networks suffer from inflexible and expen-sive equipment, and complex control-plane protocols. To address these challenges, we present SoftCell, a scalable ar-chitecture for supporting fine-grained policies for mobile de-vices in cellular core networks. The SoftCell controller real-izes high-level service polices by directing traffic over paths that traverse a sequence of middleboxes, optimized to the network conditions and user locations. To ensure scalability, the core switches forward traffic on hierarchical addresses (grouped by base station) and policy tags (identifying paths through middleboxes). This minimizes data-plane state in the core switches, and pushes all fine-grained state to soft-ware switches at the base stations. These access switches ap-ply fine-grained rules, specified by the controller, to map all traffic to the appropriate addresses and tags. SoftCell guar-antees that packets in the same connection traverse the same sequence of middleboxes in both directions, even in the pres-ence of mobility. Our characterization of real LTE work-loads, micro-benchmarks on our prototype controller, and large-scale simulations demonstrate that SoftCell improves the flexibility of cellular core networks, while enabling the use of inexpensive commodity switches and middleboxes. 1