FC & FCP: Fibre Channel and Fibre Channel Protocol

The Fibre Channel Standards (FCS) defines a high-speed data transfer mechanism that can be used to connect workstations, mainframes, supercomputers, storage devices and displays. FCS addresses the need for very fast transfers of large volumes of information and could relieve system manufacturers from the burden of supporting the variety of channels and networks currently in place, as it provides one standard for networking, storage and data transfer. Fibre Channel Protocol (FCP) is the interface protocol of SCSI on the Fibre Channel. The key Fibre Channel characters are as follows:

Performance from 266 megabits/second to over four gigabits/second
Support both optical and electrical media, working from 133 Megabits/sec up to 1062
Megabits/sec with distances up to 10 km.
Small connectors
High-bandwidth utilization with distance insensitivity
Support for multiple cost/performance levels, from small systems to supercomputers
Ability to carry multiple existing interface command sets, including Internet
Protocol (IP), SCSI, IPI, HIPPI-FP, and audio/video.

Fibre Channel consists of the following layers:

FC-0 -- The interface to the physical media
FC-1 -- The encoding and decoding of data and out-of-band physical link control information for transmission over the physical media
FC-2 -- The transfer of frames, sequences and Exchanges comprising protocol information units.
FC-3 -- Common Services required for advanced features such as striping, hunt group and multicast.
FC-4 -- Application interfaces that can execute over fibre channel such as the fibre channel protocol for SCSI (FCP).

The fundamental entity in fibre channel is the fibre channel network. Unlike a layered network architecture, a fibre channel network is largely specified by functional elements and the interfaces between them. These consist, in part, of the following:

N_PORTs -- The end points for fibre channel traffic.
FC Devices -- The fibre channel devices to which the N_PORTs provide access.
Fabric Ports -- The interfaces within a fibre channel network that provide attachment for an N_PORT.
The network infrastructure for carrying frame traffic between N_PORTs.
Within a switched or mixed fabric, a set of auxiliary servers, including a name server for device discovery and network address resolution.

The principal fibre channel network topologies consist of the following:

Arbitrated Loop -- A series of N_PORTs connected together in daisy-chain fashion.
Switched Fabric -- A network consisting of switching elements.
Mixed Fabric -- A network consisting of switches and "fabric-attached" loops. A loop-attached N_PORT (NL_PORT) is connected to the loop through an L_PORT and accesses the fabric by way of an FL_PORT.

Protocol Structure

Fibre Channel Standard structure:

FC & FCP: Fibre Channel and Fibre Channel Protocol

Fibre Channel frames are maximum 2148 bytes long. Fibre Channel Frame Header Structure:

8 bits	16 bits	24 bits	32 bits
Routine Control	Destination Address
Reserve	Source Address
Upper Level Protocol Type	Frame Control
Seq_ ID	Data Field Control	Sequence Count
Parameter