Optimistic Implementation of Bulk Data Transfer Protocols

During a bulk data transfer over a high speed network, there is a high probability that the next packet received from the network by the destination host is the next packet in the transfer. An optimistic implementation of a bulk data transfer protocol takes advantage of this observation by instructing the network interface on the destination host to deposit the data of the next packet immediately into its anticipated final location. No copying of the data is required in the common case, and overhead is greatly reduced. Our optimistic implementation of the V kernel bulk data transfer protocols on SUN-3/50 workstations connected by a 10 megabit Ethernet achieves peak process-to-process data rates of 8.3 megabits per second for 1-megabyte transfers, and 6.8 megabits per second for 8-kilobyte transfers, compared to 6.1 and 5.0 megabits per second for the pessimistic implementation. When the reception of a bulk data transfer is interrupted by the arrival of unexpected packets at the destination, the worst-case performance of the optimistic implementation is only 15 percent less than that of the pessimistic implementation. Measurements and simulation indicate that for a wide range of load conditions the optimistic implementation outperforms the pessimistic implementation

Optimistic Implementation of Bulk Data Transfer Protocols

During a bulk data transfer over a high speed network, there is a high probability that the next packet received from the network by the destination host is the next packet in the transfer. An optimistic implementation of a bulk data transfer protocol takes advantage of this observation by instructing the network interface on the destination host to deposit the data of the next packet immediately into its anticipated final location. No copying of the data is required in the common case, and overhead is greatly reduced. Our optimistic implementation of the V kernel bulk data transfer protocols on SUN-3/50 workstations connected by a 10 megabit Ethernet achieves peak process-to-process data rates of 8.3 megabits per second for 1-megabyte transfers, and 6.8 megabits per second for 8-kilobyte transfers, compared to 6.1 and 5.0 megabits per second for the pessimistic implementation. When the reception of a bulk data transfer is interrupted by the arrival of unexpected packets at the destination, the worst-case performance of the optimistic implementation is only 15 percent less than that of the pessimistic implementation. Measurements and simulation indicate that for a wide range of load conditions the optimistic implementation outperforms the pessimistic implementation

The influence of protocol choice on network performance

Bibliography: leaves 100-102.Computer communication networks are a vital link in providing many of the services that we use daily, and our reliance on these networks is on the increase. The growing use of networks is driving network design towards greater performance. The greater need for network connectivity and increased performance makes the study of network performance constraints important. Networks consist of both hardware and software components. Currently great advances are being made in network hardware, resulting in advances in the available raw network performance. In this thesis, I will show through measurement that it is difficult to harness all the raw performance and to make it available to carry network services. I will also identify some of the factors limiting the full utilization of a high speed network