Fibre Channel Overview

Working With Fibre Channel

Working With Fibre Channel

Fibre Channel is a transport protocol. Differing from protocols such as SCSI, Fibre Channel does not use data manipulation commands. An addressing scheme with advance handshaking requirements verifies that data was transferred correctly.

Fibre Channel specifications are divided into multi-layered, functional levels. The five layers define the physical media and transmission rates, encoding scheme, framing protocol and flow control, common services, and the upper-level protocol interfaces. Each section of the Fibre Channel specification can be changed without affecting other sections. Upper level specifications for Fibre Channel map commands and data from different supported protocols to the Fibre Channel system. The mapped commands and data are then segmented into frame sequences. Each frame is encoded and sent to the desired target device. At the target device, the frames are decoded and reassembled into the original sequence. The data in the sequence is extracted and then processed by the target system. This whole process is done without knowledge of the contents of the information being transferred.

Because Fibre Channel supports many different communication protocols, the highest level of the Fibre Channel specifications identify the type of communication protocol encoded. As information is divided into sequences of frames, Fibre Channel attaches address and sequence information to each packet. This transport protocol is required to reconstruct the original information into its original form.

More complex than simply dividing information up into frames and sending it to an address, Fibre Channel also has special frames to pass the following Fibre Channel-specific information between devices:

•New devices added to the system

•All device addresses

•How and when data can be transferred

•Problem detection

A-6

Appendix A