Data centers are becoming increasingly important infrastructures for many essential applications such as data intensive computing and large-scale network services. A typical future data center can consist of up to hundreds of thousands of servers. Yet, the conventional data center networks are not able to keep up with the network bandwidth requirement for efficiently connecting that huge number of servers in a cost-efficient manner. In this paper, we present DPillar, a highly scalable data

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... r interconnection architecture, which uses only low-end off-theshelf commodity PC servers and switches. DPillar has minimal requirements for the equipment. The switches are low-cost plugand-play layer-2 devices and servers are dual-port commodity PCs. The salient feature of DPillar is that it expands to any number of servers without requiring to physically upgrade the existing servers. We present simple yet efficient routing schemes for DPillar and evaluate the routing performance via simulations.