Enhanced PVM communications over a high-speed LAN

Performance results of PVM over a local ATM network show the availability of much greater communication bandwidth over traditional LANs such as Ethernet. Application-level performance, however, still lags far behind the capabilities of the physical medium. Realizing the full potential of high-speed networks, therefore, will require further improvements in both hardware and software components of network I/O subsystems.Emulating a parallel machine via a collection of heterogeneous, independent hosts and a general-purpose local-area network has obvious advantages, including cost-effectiveness and very large aggregate processing power and memory. However, the ability of most general-purpose LANs to support communication-intensive parallel applications is debatable. Today, with the emergence of several high-speed, switch-based networks, such as High-Performance Parallel Interface (Hippi), Fibre Channel, and Asynchronous Transfer Mode (ATM), networks that effectively support communication-intensive parallel applications may soon become a reality.Network-based computing offers several advantages. First, independent, commercially available systems and a general LAN can readily incorporate advances in processor and network technology. Second, due to the large memory and processing power available in the aggregate collection of individual host systems, very large applications can execute on a collection of relatively low-priced host systems. Third, the underlying network can support high-speed input/output to applications, for instance, by using disk arrays.One factor that previously fueled much skepticism about the feasibility of network-based parallel computing was the limitations imposed by using traditional LANs, such as Ethernet, as the system interconnect. For many typical network applications that require only occasional file transfers, or infrequent small amounts of data to be transmitted between workstations, an Ethernet-based cluster of workstations will suffice. However, for network-based applications, such as communication-intensive, course-grain parallel applications, traditional networks such as Ethernet simply cannot provide adequate performance. Thus, for this study, we chose a high-speed transport mode as the supporting communication medium.