GNET-1 is a fully programmable network testbed. It provides functions such as wide area network emulation, network instrumentation, trac shaping, and trac generation at gi- gabit Ethernet wire speeds by programming the core FPGA. GNET-1 is a powerful tool for developing network-aware grid software. It is also a network monitoring and trac-shaping tool that provides high-performance communication over wide area networks. This paper describes several sample uses of GNET-1 and presents its architecture.