Recent advances in commodity network interface technology enable scientists and engineers to build clusters of workstations or PCs to execute parallel applications. However, raw-hardware network performance is rarely delivered to applications because of the overheads of communication software and operating systems. To reduce these overheads, a technique called user-level communication can be used to allow applications to access the network interface directly without intervention from the operating system. In this paper we examine two user-level communication systems, GM and BIP, on alpha based systems connected by a Myrinet network. In addition quantitative studies on how DMA initiation costs, flow control and reliable communication will effect the performance of communication software are presented.