Friends or foes: Revisiting strategy-proofness in cloud network sharing

Cloud networks consist of a large number of links, on which tenants have correlated and elastic bandwidth demands in the form of coflows. Ideally, a cloud network sharing policy should provide tenants with isolation guarantees on the minimum coflow progress, while at the same time attaining as high utilization as possible. Prior work shows that to achieve the optimal isolation guarantee, strategy-proofness is needed, in that tenants cannot lie about demands to obtain higher progresses. However, this requirement is derived under a simplified assumption that tenants are only interested in maximizing coflow progresses. We show in this work that a rational tenant should pursue more bandwidth allocation as a secondary objective after progress maximization. In this new model, enforcing strategy-proofness inevitably hurts the isolation guarantee. We propose a new network sharing policy to achieve the optimal isolation guarantee while attaining the highest possible utilization in spite of strategic, untruthful tenants. Trace-driven evaluations show that our policy outperforms existing alternatives with better isolation guarantee, higher utilization, and shorter coflow completion time (CCT).