On the efficacy of fine-grained traffic splitting protocols in data center networks

Current multipath routing techniques split traffic at a per-flow level because, according to conventional wisdom, forwarding packets of a TCP flow along different paths leads to packet reordering which is detrimental to TCP. In this paper, we revisit this "myth" in the context of cloud data center networks which have regular topologies such as multi-rooted trees. We argue that due to the symmetry in the multiple equal-cost paths in such networks, simply spraying packets of a given flow among all equal-cost paths, leads to balanced queues across multiple paths, and consequently little packet reordering. Using a testbed comprising of NetFPGA switches, we show how cloud applications benefit from better network utilization in data centers.