dcPIM: near-optimal proactive datacenter transport

Datacenter Parallel Iterative Matching (dcPIM) is a proactive datacenter transport design that simultaneously achieves near-optimal tail latency for short flows and near-optimal network utilization, without requiring any specialized network hardware.

dcPIM places its intellectual roots in the classical PIM protocol, variations of which are used in almost all switch fabrics. The key technical result in dcPIM is a new theoretical analysis of the PIM protocol for the datacenter context: we show that, unlike switch fabrics where PIM requires log(n) rounds of control plane messages (for an n-port switch fabric) to guarantee near-optimal network utilization, the datacenter context enables PIM to guarantee nearoptimal utilization with constant number of rounds (independent of the number of hosts in the datacenter)! dcPIM design builds upon insights gained from this analysis, and extends the PIM design to overcome the unique challenges introduced by datacenter networks (much larger scales and round trip times when compared to switch fabrics). We demonstrate, both theoretically and empirically, the near-optimality of dcPIM performance.