Performance considerations in designing network interfaces

Design issues that affect the performance of network input/output (I/O) are examined by analyzing the design and performance of a workstation´s network interface to the 100-Mb/s FDDI token ring. Several design alternatives for partitioning functions between the network interface and the host software are evaluated. A simple model is proposed for looking at the performance of network I/O, and an effective analysis approach for predicting user-perceived throughput is demonstrated. The analysis reveals that, particularly for network interfaces that reside on an I/O bus, providing a DMA engine for data movement provides significant improvements in throughput. However, the designs for the receive and transmit sides are not necessarily symmetrical, and it is shown that host architecture considerations influence the design of each direction differently. The analysis is used to show the potential benefits of having all protocol functions on the network interface and also to point out the potential processing power needed on that network interface