Page 10 of 18 Fibre Channel: Why another interface? March 2001 The Fibre Channel protocol defines five functional levels, which separate the processes involved in data transmission from the processes involved in high-level command set decoding. The first four levels (FC-0 through FC-3) are concerned with the physical and logical mechanics of the data transmission. The fifth level (FC-4) defines the mapping of device-specific command protocols like SCSI onto the signaling and data transmission protocols of the Fibre Channel interface. It is only at this level that the host CPU and software become involved in decoding the bit patterns representing the device-specific command set and performing higher-level processes. Three ways to connect Fibre Channel supports three different logical or physical arrangements (topologies) for connecting the devices into a network: point-to-point, arbitrated loop, and switched fabric. In all of these topologies, a transmitter node in one device sends information to a receiver node in another device. The physical connection between devices varies from one topology to another. Fibre Channel performs data encoding, transport, flow control, and error handling at the hardware level High-level command protocol processing SCSI Mapping layer (FC-4) IP HIPPI Others... Frame/Sequence/Exchange Protocol multiplexing Flow control Error detection/retransmission Request-response coupling Segmentation and reassembly Link control and services Composite transport, network, and data link layers (FC-2 and FC-3) Encode-decode Transmission speed Media (copper, fiber optic) Physical layers (FC-0 and FC-1) The Fibre Channel protocol separates the physical and logical aspects of data transfer that are common to all devices on the network from the device-specific, high-level command processing operations. p1   p2   p3   p4   p5   p6   p7   p8   p9   p10   p11   p12   p13   p14   p15   p16   p17   p18