Increasing Datacenter Network Utilisation with GRIN

Various full bisection designs have been proposed for datacenter networks. They are provisioned for the worst case in which every server sends flat out and there is no congestion anywhere in the network. However, these topologies are prone to considerable underutilisation in the average case encountered in practice. To utilise spare capacity we propose GRIN, a simple, cheap and easily deployable solution that simply wires up any free ports datacenter servers may have. GRIN allows each server to use up to a maximum amount of bandwidth dependent on the number of available ports and the distribution of idle uplinks in the network. Our evaluation found significant benefits for bandwidth-hungry applications running over our testbed, as well as on 1000 EC2 instances. GRIN can be used to augment any existing datacenter network, with a small initial effort and no additional maintenance costs.