This project involves designing and implementing an ATM network transport called Guaranteed ATM.  ATM’s philosophy does not guarantee the delivery of data since many new network demands, such as voice and video, do not need all data to reach its destination.  Applications that do require a delivery guarantee must provide it in software.  Fore Systems, a leader in ATM technology, provides a good starting point with its simple hardware interface, so Guaranteed ATM lies on top of Fore’s interface providing a system of error and flow control.  The layer lives up to its name of “Guaranteed” thanks to a succession of torture tests.   After optimization, the primary bottlenecks exist outside of the Guaranteed ATM layer.  The conclusion reveals ways to enhance future performance including integration with Fore System’s interface and synchronization enhancements.