A Distributed Hybrid Load Management Model for Anycast CDNs

Anycast content delivery networks rely on the underlying routing to schedule clients to their nearby service nodes, which however is not natively aware of server load or path latency. Requests burst from some regions may cause overload and hurt user experience. This scenario demands quickly adjusting clients to other nearby servers with available capacity. However, state-of-the-art solutions do not work well. On one hand, native routing-based scheduling is not flexible and precise enough, which may cause cascading damage and interrupt ongoing sessions. On the other hand, centralized algorithm is vulnerable and not responsive due to high complexity. We propose a practical distributed hybrid load management model to solve load burst problem. First, the hybrid mechanism leverages flexible DNS-based redirection, which can schedule at per-request granularity without interrupting ongoing sessions. Second, the distributed model is responsive by reducing computation overhead and theoretically guarantees to converge to the optimal solution. Based on the model, we further propose an cooperative and two heuristic distributed algorithms. At last, using a measurement dataset, we demonstrate their effectiveness and scalability, and illustrate how to adapt them to different scenarios.