Fibre Channel Technology

Fibre Channel is a network technology primarily used for storage networking , which was first available at the speed of 1 Gbps and then at 2, 4 and now 8 Gbps. In our one article named Distributed Caching for Storage Acceleration, we mentioned about Fibre Channel and Fibre Channel over Ethernet. In this article, we will specifically discuss on Fibre Channel (NOT Fibre Channel over Ethernet).

What is Fibre Channel ?

Fibre Channel is standardized by the T11 Technical Committee of International Committee for Information Technology  Standards, accredited by the ANSI. Fibre Channel was born for faster connection in supercomputing , but has been adapted in connection type for storage area networks in business. The nomenclature Fibre Channel is somewhat a misnomer, fiber channel signaling can operate over copper wire pairs not only with optical fiber cables. The working protocol of Fibre Channel Technology is FCP (Fibre Channel protocol).

Fibre Channel began its development back in 1988, after the approval of the standard by ANSI in 1994 as a way to simplify the HIPPI , which was in use for similar usage at that time. HIPPI used hose connectors of 50 pairs and was very large and had limitation in the length of the cables. The fiber channel was particularly interesting to simplify the connections and increase the length rather than to increase the speed. Fibre Channel later expanded its application to disk storage, allowing higher speeds and a support to a much larger number of devices.

Fibre Channel Technology : Behind the Cables

A link in the fiber channel consists of two unidirectional fibers transmitting in opposite directions. Each fiber is attached to a transmitter port (TX) and a receiver port (RX). Depending on the connections between the different elements, we can distinguish three main topologies Fibre Channel :

• Point-to-point (FC-P2P)
• Arbitrated loop (FC-AL)
• Switched fabric (FC-SW

Fibre Channel has five layers, not abiding OSI model :

1. FC0 is physical layer, including cables, fiber optics, connectors, etc..
2. FC1 is data link layer, which implements the coding and decoding of signals.
3. BC2 is network layer, which defined by the standard of FC-PI-2, which is the core of the fiber channel and defines the main protocols.
4. FC3 is common services layer, a thin layer that can implement functions like encryption.
5. FC4 layer is for protocol mapping, in which other protocols, such as SCSI, are delivered to the FC2 layer.

FC0, FC1 and FC2 are also known as FC-PH Physical layers of fiber channel. Fibre Channel implementations are available at 1 Gbps, 2 Gbps and 4 Gbps speed. A standard 8 Gbps is under development. A 10 Gbps development has been ratified, but it is currently only is used to interconnect switches. Products based on the standard 1, 2, 4 and 8 Gbps must be interoperable and backward compatible for 10 Gbps standard.

Fibre Channel ports are not mentioned here to avoid complexity of understanding by a new user. Host bus adapters for Fibre Channel has a unique identifier name, similar to the MAC address in Ethernet.