IBM SAN16B-2 - TotalStorage Express Model Switch User And Service Manual page 72

asynchronous transfer mode (ATM). A method of
transmission in which the sending and receiving of data
is controlled by control characters such as a start bit
and a stop bit, instead of by a timing sequence.
ATM. See asynchronous transfer mode.
autonegotiation. A universal mechanism to exchange
network capabilities between two Ethernet nodes. The
exchange takes place at power-up (or link reset) time. It
automatically establishes a link that takes advantage of
the highest common denominator of the mutual
capabilities of the two Ethernet nodes. The universal
mechanism negotiates capabilities that include link
speed, PHY types, and full duplex or half duplex.
autoranging. A power supply that accommodates
different input voltages and line frequencies.
AW_TOV. See arbitration wait timeout value.
B
backup FCS switch. The switch or switches assigned
as backup in case the primary fabric configuration
server (FCS) switch fails. See also fabric configuration
server switch and primary FCS switch.
bandwidth. (1) The total transmission capacity of a
cable, link, or system. Usually measured in bits per
second (bps). (2) The range of transmission frequencies
available to a network. See also throughput.
basic input/output system (BIOS). Code that controls
basic hardware operations, such as interactions with
diskette drives, hard disk drives, and the keyboard.
BB_credit. See buffer-to-buffer credit.
beacon. When all the port light-emitting diodes (LEDs)
on a switch are set to flash from one side of the switch
to the other, to enable identification of an individual
switch in a large fabric. A switch can be set to beacon
by a CLI command or through Web Tools.
beginning running disparity. The disparity at the
transmitter or receiver when the special character
associated with an ordered set is encoded or decoded.
See also disparity.
BER. See bit error rate.
BIOS. See basic input/output system.
BISR. Built-in self-repair.
BIST. Built-in self-test.
bit error rate (BER). The rate at which bits are
expected to be received in error. Expressed as the ratio
of error bits to total bits transmitted. See also error.
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SAN16B-2 Installation, Service, and User's Guide
blade. A component that provides application-specific
services and components. A blade is typically a hot
swappable hardware device.
block. As applies to Fibre Channel, upper-level
application data that is transferred in a single sequence.
boot code. Software that initialized the system
environment during the early phase of the boot-up
process. For example, boot code might determine the
amount of available memory and how to access it.
boot flash. Flash memory that stores the boot code
and boot parameters. The processor runs its first
instructions from boot flash. Data is cached in random
access memory (RAM).
British thermal unit (Btu). The amount of heat
required to raise a pound of water by 1 degree
Fahrenheit.
broadcast. The transmission of data from a single
source to all devices in the fabric, regardless of zoning.
See also multicast and unicast.
Btu. See British thermal unit.
buffer-to-buffer credit. The number of frames that
can be transmitted to a directly-connected recipient or
within an arbitrated loop. Determined by the number of
receive buffers available. See also buffer-to-buffer flow
control.
buffer-to-buffer flow control. Management of the
frame transmission rate in either a point-to-point
topology or in an arbitrated loop. See also
buffer-to-buffer credit.
C
CAM. Content addressable memory.
cache. A buffer that contains frequently accessed
instructions and data; it is used to reduce access time.
cascade. Two or more interconnected Fibre Channel
switches that can build large fabrics. Switches can be
cascaded up to 239 switches, with a recommended
maximum of seven inter-switch links (no path longer
than eight switches). See also fabric and inter-switch
link.
central processing unit (CPU). The part of a
computer that includes the circuits that control the
interpretation and running of instructions. A CPU is the
circuitry and storage that executes instructions.
Traditionally, the complete processing unit was often
regarded as the CPU, whereas today the CPU is often
a microchip. In either case, the centrality of a processor
or processing unit depends on the configuration of the
system or network in which it is used.