ANSI standard Fibre Channel is emerging as the networking protocol of choice for high bandwidth applications. Fibre Channel is an enabling technology because of the tremendous advantages in speed and latency it provides over existing networking technologies. Applications which weren't feasible before are now possible and more will follow which demand this performance. Fibre Channel is the high performance alternative to existing networking technologies such as FDDI, Fast Ethernet, and ATM.rnFibre Channel (FC) provides for 2 different data communication models, connection and connectionless. Although interoperable, some of these implementations may not result in optimal performance. For example, applications for disk attach typically use FC class 2 with large frame sizes for data transfer. Client/server applications in imaging are using large class 1 frames. There is some disagreement in the FC community as to which is more appropriate. Both have their advantages and disadvantages and so its necessary to look at each application individually. This paper addresses some of these issues by simulating these 2 communication models over different switch architectures.rnThe Ancor switch architecture supports a data communication model which utilizes FC class 1 (connection) to transfer the application data and FC class 2 (connection-rnless) to transfer protocol control, link management, and error control information. Other FC users have continued using FC class 2-only. However, class 2-only communication in FC shows a decrease in performance when heavier traffic flows occur. Data is presented which shows that small buffer sizes, when used in conjunction with the class 1 data communication model, provides networking performance which surpasses class 2-only networks under loaded conditions or with longer I/O request sizes. Ancor's unique switched FC implementation alleviates congestion that causes poor performance by demultiplexing the two types of traffic (connection and connectionless) and providing independent paths for each through the switch. This is 2-dimensional switching and is discussed in more detail later.rnAnother area of interest in the FC community has been the choice of frame size for class 2. FC allows payload sizes up to 2048 bytes. Because each frame contains a fixed size header and trailer, there is overhead with each frame. The larger the frame size, the lower the overhead. The performance difference between large and small frames turns out to be less than one might expect because of the effects of smaller protocol control frames intermixed with the larger frames. The effects of frame size are explored to see exactly what the relative performance differences are between the different payload sizes.
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