Fibre Channel aims to provide inexpensive, yet scalable data transfer. Fibre Channel is a hybrid between a network and a channeling system; it is like a network in that it uses a flexible set of switches, called a fabric, but that Fibre channel ports have to manage simple end to end connections. Fibre Channel pioneered many of the protocol changes that are have now been implemented in Gb IP such as large packages. Fibre channel packages have a 2KB payload, much more than typical IP packages.
The switch connecting Fibre channel devices are called the fabric. The fabric can be a circuit switch, a hub, or a loop.
Fibre Channel is standardized using five layers:
- FC-4: Upper Layer Protocol Interface supports VI, IP, and most importantly, serial SCSI-3 (FCP). The task of FCP is to make fibre channel devices appear as standard SCSI devices to each other. This strategy avoids OS modifications in the storage servers.
- FC-3: Common Services, is currently under development and will contain such services as striping a transmission over several ports, hunt groups that allow more than one port to respond to the same alias address (in order to decrease chances of hitting on a busy port), and multicasting.
- FC-2: Data Delivery codifies framing, flow control and service class. A fibre channel frame consists of 32B frame meta data framing a 2112 B data field that contains up to 2048B payload. The fiber channel service classes allow either an in effect a virtual physical connection (class 1), or packet switched connections with (class 1) or without (class 2) acknowledgments.
- FC-1: Ordered sets / byte encoding.
- FC-0: Physical interface (optical/electrical, cable plant).
Fibre channels upper layer protocols and its pioneering high transfer rates have made the technology vulnerable to competitors that use Gb IP as the connection. One such possibility is iFCP which provides Fibre channel fabric services to figre channel end devices over a high-speed TCP/IP network.
Figure 1: Fibre Channel Layers (Meggyesi)
Additional ReferencesMeggyesi: Fibre Channel Overview
|© 2003 Thomas Schwarz, S.J., COEN, SCU SCU COEN T. Schwarz COEN 180|