Fibre Channel
Fibre Channel is a serial computer bus intended for connecting high speed storage devices to computers. It started for use primarily in the supercomputer field, but has become the standard connection type for storage area networks in enterprise storage. Despite its name, Fibre Channel signaling can run on both twisted-pair copper wire and fiber optic cables.
Fibre Channel started in 1988 as a way to simplify the HIPPI system currently in use for similar roles. HIPPI used a massive 50-pair cable and gigantic connectors, and had limited cable lengths. Fibre Channel was primarily interested in simplifying the connections and increasing the lengths, as opposed to increasing speeds. Later it broadened its focus to address SCSI disk storage, providing higher speeds and far greater numbers of connected devices.
It also added support for any number of "upper layer" protocols, including SCSI, ATM and IP, with SCSI being the predominant usage.
There are three major Fibre Channel topologies:
- Point-to-Point (FC-P2P). Two devices are connected back to back. This is the simplest topology with limited connectivity.
- Arbitrated Loop (FC-AL). In this design, all devices are in a loop or ring, similar to token ring networking. Adding or removing a device from the loop causes all activity on the loop to be interrupted. The failure of one device causes a break in the ring. Fibre Channel hubs exist to connect multiple devices together, or a simple point-to-point connection can be made. An arbitrated loop with two devices degenerates to point-to-point topology.
- Switched Fabric (FC-SW). All devices are connected to Fibre Channel switches, similar conceptually to modern Ethernet implementations. The switches manage the state of the fabric, providing optimized interconnections and also security.
Fibre Channel, like many protocols, is a layered protocol. It consists of 5 layers, namely:
- FC0 The physical layer that includes cables, fiber optics etc.
- FC1 The data link layer which implements the 8b/10b encoding and decoding of signals.
- FC2 The network layer, defined by the FC-PH standard, consists of the core of FC.
- FC3 A thin layer that implememts auxilary functions that span across multiple ports on a Fibre Channel device.
- FC4 Application layers, or upper layer protocol encapsulation. This layer is responsible for encapsulation of various upper layers over FC.
See also
Host Bus Adapter, Fibre Channel zoning,
IDE, ATA, SATA, SCSI, iSCSI
