Juggler: a practical reordering resilient network stack for datacenters

We present Juggler, a practical reordering resilient network stack for datacenters that enables any packet to be sent on any path at any level of priority. Juggler adds functionality to the Generic Receive Offload layer at the entry of the network stack to put packets in order in a best-effort fashion. Juggler's design exploits the small packet delays in datacenter networks and the inherent burstiness of traffic to eliminate the negative effects of packet reordering almost entirely while keeping state for only a small number of flows at any given time. Extensive testbed experiments at 10Gb/s and 40Gb/s speeds show that Juggler is effective and lightweight: it prevents performance loss even with severe packet reordering while imposing low CPU overhead. We demonstrate the use of Juggler for per-packet multi-path load balancing and a novel system that provides bandwidth guarantees by dynamically prioritizing packets.