The testbed we used to evaluate the two systems is an 8-node cluster of HP9000-735/125 workstations, each with a 125Mhz PA-RISC7100 processor and 96 megabytes of main memory. The machines have a 4096-byte page size and are connected by a 100Mbps FDDI ring.
In TreadMarks, the user processes communicate with each other using UDP. In PVM, processes set up direct TCP connections with each other. Since all the machines are identical, data conversion to and from external data representation is disabled. Both UDP and TCP are built on top of IP, with UDP being connectionless and TCP being connection oriented. TCP is a reliable protocol while UDP does not ensure reliable delivery. TreadMarks uses light-weight, operation-specific, user-level protocols on top of UDP to ensure reliable delivery.
Rice Systems Group