Optimizing Cache Location and Route on CDN Using Model Predictive Control

In content delivery services, cache-server selection and route control are independently operated by content delivery network (CDN) providers and Internet service providers (ISPs), respectively. However, the number of ISPs providing CDN service has been increasing, and they can optimize the cache-server and delivery-route selection simultaneously. In this paper, we investigate the effect of jointly controlling these two operations. To continuously maintain a desirable state over a long time span in an environment in which estimating future demand is not easy, we should use an optimization method with which we can repeat the optimization procedure continuously. Therefore, we propose a method of optimizing the cache-server selection using the model predictive control (MPC), which has been widely used in system control. We also propose a method of simultaneously optimizing both the cache-server and delivery-route selection using the MPC. Through numerical evaluation using two actual network topologies of Tier-1 ISPs and the access log data of VoD services, we confirm that we can achieve almost the same effect by optimizing only cache-server selection using the MPC compared with optimizing both operations simultaneously. We also confirm that the number of failed requests that are not accommodated in the system can be reduced by about 1/30 with the proposed methods using the MPC.