Facing the rising tide of scientific data traffic generated by sophisticated supercomputers, specialized facilities such as the Large Hadron Collider, and largescale international scientific collaborations, ESnet is ensuring future capacity with the Advanced Networking Initiative (ANI). This $62 million stimulus investment funded by the Department of Energy Office of Science includes a the world’s first 100 gigabit-per-second (Gbps) transcontinental scientific network, a wholly DOE-owned network of almost 13,000 miles of dark fiber, and a nationwide research test bed for researchers to experiment in a production environment with the advanced technologies that will build the future Internet. The testbed already boasts dozens of projects, and accepts new proposals semiannually. The ANI 100 Gbps prototype network now connects three DOE supercomputing centers at Argonne, Oak Ridge, and Lawrence Berkeley National Laboratories and the Manhattan Landing exchange point (MANLAN). ESnet will integrate all DOE laboratories into the ANI infrastructure by the end of 2012, when the prototype network is transitioned to the permanent ESnet5 network.