Universally Stable Cache Networks
Yuanyuan Li, Stratis Ioannidis · 2020
We consider a cache network in which intermediate nodes equipped with caches can serve content requests. We model this network as a universally stable queuing system, in which packets carrying identical responses are consolidated before being forwarded downstream. We refer to resulting queues as M/M/1c or counting queues, as consolidated packets carry a counter indicating the packet's multiplicity. Cache networks comprising such queues are hard to analyze; we propose two approximations: one via M/M/∞ queues, and one based on M/M/1c queues under the assumption of Poisson arrivals. We show that, in both cases, the problem of jointly determining (a) content placements and (b) service rates admits a poly-time, 1 1/e approximation algorithm. Numerical evaluations indicate-that both approximations yield good solutions in practice, significantly outperforming competitors.