Nodes in a P7-IH [20] cluster are connected in a two-level dragon-fly network topology. The core of the network is the Hub Chip, which connects several high-bandwidth links using a high-performance in-ternal crossbar switch. These links, providing over 9 Tbits/second of raw bandwidth, are used to build a two-level topology spanning up to tens of thousands of POWER7 processor chips, offering high bisection bandwidth and low latency.