Throughput Analysis Between High End Workstations Across an FDDI network

Recently developed high speed networks are capable of transmitting data at rates of 100 Mbps or more. One such network protocol is Fiber Distributed Data Interface FDDI. This network has a physical transmission rate of 100 Mbps. Analytical and simulation studies have shown that the FDDI protocol should provide actual throughput of 80 to 95 of this physical rate. Can the end user expect to see this kind of performance If not, then what kind of throughput can actually be expected and where are the bottle necks In order to answer these and other related questions, two areas were studied First, a performance comparison between a 40MHz SPARCstation 10 workstation and a 5OMHz SPARCstation 10 workstation was conducted using the Neal Nelson commercial benchmark tool. Next, a well-known network measurement tool, ttcp, was used to obtain data transfer rates while varying several tunable operating system and network parameters. The parameters varied were Target Token Rotation Time, TCP IP window size, NFS asynchronous threads. Logical Link buffer size and Maximum Transfer Unit size. The results from the commercial benchmark analysis were used to determine if there are any differences which can affect transfer rates between the two workstations. The results from the commercial benchmark tool clearly showed that the newer, higher speed processor is faster. The network tool ttcp showed that the TCPIP window size had the largest impact on throughput performance. Throughput more than doubles from a window size of 4k to a window size of 20k.