Chandu Thekkath and Geoff Voelker contributed to the original gms_net implementation, and some of the ideas in this paper originated with them. Hank Levy and Anna Karlin have contributed to all aspects of the GMS project. We thank Bob Felderman at Myricom and Mark Shand, Don Rice, Marc Viredaz and Lance Berc at Digital for help with the hardware, and Gretta Bartels for help preparing the document.