DiFS: Distributed flow scheduling for adaptive routing in hierarchical data center networks

Data center networks leverage multiple parallel paths connecting end host pairs to offer high bisection bandwidth for cluster computing applications. However, state of the art routing protocols such as Equal Cost Multipath (ECMP) is load-oblivious due to static flow-to-link assignments. They may cause bandwidth loss due to flow collisions. Recently proposed centralized scheduling algorithm or host based adaptive routing that require network-wide condition information may suffer from scalability problems. In this paper, we present Distributed Flow Scheduling (DiFS) based Adaptive Routing for hierarchical data center networks, which is a localized and switch-only solution. DiFS allows switches to cooperate to avoid over-utilized links and find available paths without centralized control. DiFS is scalable and can react quickly to dynamic traffic, because it is independently executed on switches and requires no synchronization. DiFS provides global bounds of flow balance based on local optimization. Extensive experiments show that the aggregate throughput of DiFS using various traffic patterns is much better than that of ECMP, and is similar to or higher than those of two representative protocols that use network-wide optimization.