A network interface is a device that allows a computer to communicate with a network. Network interface design has a crucial impact on communication efficiency. It determines the cost of communication actions, moving data, and providing application isolation across communicating domains. With the advent of distributed computing and the Internet, and with dramatically faster processor clock rates and complete systems on chips, computing is increasingly concerned with the efficient movement of data-across the interconnects within a machine, the system area network within a machine room, and the local area or wide area network. The authors discuss network interface design issues.