Page 6 of 18 Fibre Channel: Why another interface? March 2001 Networks are designed to handle many small packets of data with many different sources and destinations simultaneously. During a network data transfer, blocks of data or information units are encapsulated into packets. These packets all have a consistent structure, regardless of the type of data they contain. Each packet includes header and addressing information to ensure delivery to the correct recipient. The completed packets are transferred one at a time along a single wire. When a packet reaches its destination, the recipient CPU or software “digests” the packet to extract the data it contains, ensures that the data is reassembled in the correct order, performs error correction activities, and decodes the bit patterns representing the device-specific command set. The network protocol defines the packet structure and electrical characteristics of the signal used to transport data on the cable. It is not concerned about what the data inside the packet is or how it is formatted. By design, networks automatically adjust to changing environments and can support a larger number of connected devices (or nodes). In addition, because the network interface hardware does not interact directly with the data inside the packet, systems that use different command sets and high-level protocols can share the network. In traditional 10/100 BaseT Ethernet networks, the distance and simplicity advantages of serial data transmission are offset by a reduced data transfer rate. Not only is the data transferred one bit at a time, but the unstructured, unpredictable nature of networks requires a significant amount of software involvement in performing the decision making required to successfully route data from one point to another. As a result, networks are inherently slower and have a higher processor overhead than dedicated buses. A network encapsulates multiple bits of data into a packet and transmits them one at a time over a single line Network Interface Card Server Buffer Network Data Printer Workstation Serialized data is encapsulated and transmitted one packet at a time. In a typical network environment, the sending and receiving processors must perform the data serialization and reassembly and perform error correction. This processor overhead can have a dramatic negative impact on other processor operations. p1   p2   p3   p4   p5   p6   p7   p8   p9   p10   p11   p12   p13   p14   p15   p16   p17   p18