: Ensemble Routing For Datacenter Networks Mike Schlansker, Yoshio Turner, Jean Tourrilhes, Alan Karp HP Laboratories HPL-2010-120 Networks, Ethernet, Multipath, Switching, Fault Tolerance This paper describes Hash-Based Routing (HBR), an architecture that enhances Ethernet to support dynamic management for multipath networks in scalable datacenters. This work enhances HBR to support flow ensemble management for large-scale networks of arbitrary topology. Ensemble routing eliminates measurement and control for individual flows and instead manages using summary data thus providing a unique capability for reactive datacenter-wide network management. HBR provides seamless interoperability with Ethernet and supports the attachment of unmodified L2 hosts and devices including FCoE devices within converged fabrics. Simulation experiments demonstrate efficient multipath routing for a variety of scalable topologies. Optimized routing maintains efficiency in the presence of network faults and ...