A significant drive to consolidate data center networks on a single infrastructure is taking place. 10-Gigabit Ethernet is one of the contenders to fulfill the role of universal data center interconnect. One of the key features missing from conventional Ethernet is congestion management; this void is being filled by the standardization work of the IEEE 802.1Qau working group. However, the schemes under consideration react to congestion only at the sources by reducing the transmission rates of "hot" flows, i.e., those detected as contributing to congestion. This approach ignores a crucial aspect of many data center networks, namely, that there typically are multiple paths between any pair of end nodes. Before reducing transmission rates, it would make sense to look for an alternative, uncongested path first. Here, we propose an adaptive routing scheme that builds-in a fully transparent way-on top of the existing 802.1Qau schemes, by snooping the congestion notification frames to modify the routing behavior of the switching nodes. We demonstrate how this can lead to significant performance improvements by taking full advantage of path diversity.
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