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Appendix A Glossary
Some terms used in the Fibre Channel industry are defined below. More information is available through the ATTO
Technology website (
www.attotech.com
), the Fibre Channel Industry Association (
www.fibrechannel.com
),
Cern (
www.cern.ch
), the Storage Area Networking Industry Association (
www.snia.org
), and the Fibre Channel
Consortium (
www.iol.unh.edu/consortiums
, click on FC).
Term Definition
ANSI American National Standards Institute
arbitrate process of selecting one L_Port from a collection of ports which ask for use of the arbitrated loop
at the same time
arbitrated loop a loop topology (FC-AL) in which two or more ports are interconnected, but only two ports can
communicate at one time; low-cost solution which may or may not use hubs and switches
auto negotiation hardware senses and automatically responds depending on configuration
BER Bit Error Rate: a measure of transmission accuracy; the ratio of bits received in error to bits sent
bit smallest unit of data a computer can process: a single binary digit with a value of either 0 or 1
bus a collection of unbroken signal lines used to transmit information from one part of a computer
system to another; taps on the lines connect devices to the bus
byte an ordered set of 8 bits
channel a point-to-point link which transports data from one point to another
CPU Central Processing Unit: the portion of the computer that actually performs computations
CRC Cyclic Redundancy Check: an error-correcting code which calculates a numeric value for received
and transmitted data; if no error has occurred during transmission, the CRC for both received and
transmitted data should be the same
destination
address
a value in the frame header of each frame which identifies the port in the node where the frame is
being sent
device driver a program that allows a microprocessor to direct the operation of a peripheral device
DMA Direct Memory Access: a way to move data from a storage device directly to RAM without using
the CPU’s resources
DMA bus master allows a peripheral to control the flow of data to and from system memory by block as opposed to
allowing the processor to control the data by bytes (PIO or programmed I/O)
fabric a Fibre Channel switch of two or more Fibre Channel switches interconnected to physically transmit
data between any two N_Ports on the switch or switches
FC Fibre Channel
F_port a port in the Fibre Channel fabric where a N_port may attach
FL_port a port in the Fibre Channel fabric where a NL_port may attach in an arbitrated loop
frame an indivisible unit for transfer of information in Fibre Channel
frame header the first field in the frame containing the address and other control information about the frame
full-duplex a communication protocol which allows transmission in both directions at the same time
half duplex a communication protocol which allows transmission in both directions, but only one direction at a
time
host a processor, usually a CPU and memory, which communicates with devices over an interface
initiator device a component which originates a command
L_port a port in an arbitrated loop, either a NL_port or a FL_port
LED Light-emitting diode: a type of diode that emits light when current passes through it; visible LEDs
are used as indicator lights on all sorts of electronic devices
LUN Logical Unit Number: an identifier for a logical unit (0-7)
multi-mode fiber an optical fiber which can carry several beams of light at once