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control message interface (CMI).

A set of control

signals that are used to pass hardware-level messages
between ports.

control processor (CP).

The central processing unit

that provides all control and management functions in a
switch.

CP.

See

control processor

CPLD.

Complex programmable logic device.

CPU.

See

central processing unit

CRC.

See

cyclic redundancy check

credit.

The number of receive buffers allocated to a

transmitting node port (N_port), node loop port
(NL_port), or fabric port (F_port). The credit is the
maximum number of outstanding frames that can be
transmitted by that N_port, NL_port, or F_port without
causing a buffer overrun condition at the receiver.

cyclic redundancy check (CRC).

A check for

transmission errors included in every data frame.

data rate.

The rate at which data is transmitted or

received from a device. Interactive applications tend to
require a high data rate, while batch applications can
usually tolerate lower data rates.

DDR.

Double data rate. See

data rate

defined zone configuration.

The complete set of all

zone objects that are defined in the fabric. The defined
configuration may include multiple zone configurations.
See also

zone configuration

destination ID (DID).

The 3-byte destination ID of the

destination device, in the 0xDomainAreaALPA format.

device.

Hosts and storage that connect to a switch.

Example devices are servers, redundant array of
independent disks (RAID) arrays, and tape subsystems.

DID.

See

destination ID

direct memory access (DMA).

The transfer of data

between memory and an input/output (I/O) device
without processor intervention.

disk operating system (DOS).

An operating system

for personal computers that can only perform tasks one
at a time.

disparity.

The relationship of ones and zeros in an

encoded character.

Neutral disparity

means an equal

number of each,

positive disparity

means a majority of

ones, and

negative disparity

means a majority of zeros.

DLS.

See

dynamic load sharing

DMA.

See

direct memory access

domain_ID.

A unique identifier for the switch in a

fabric. The domain_ID is usually automatically assigned
by the switch, but can also be assigned manually. The
values of domain_ID can be a value between 1- 239.

DOS.

See

disk operating system

DRAM.

See

dynamic random access memory

DWDM.

Dense wavelength digital multiplexing.

dynamic load sharing (DLS).

Dynamic distribution of

traffic over available paths. Allows for recomputing of
routes when a fabric port or fabric loop port (Fx_port) or
expansion port (E_port) changes status.

dynamic random access memory (DRAM).

storage in which the cells require repetitive application
of control signals to retain stored data.

E_D_TOV.

See

error detect timeout value

EE_credit.

See

end-to-end credit

effective configuration.

The particular zone

configuration that is currently in effect. Only one
configuration can be in effect at once. The effective
configuration is built each time a zone configuration is
enabled.

EIA.

Electronic Industry Association.

EIA rack.

A storage rack that meets the standards set

by the Electronics Industry Association (EIA).

electromagnetic compatibility (EMC).

The design

and test of products to meet legal and corporate
specifications dealing with the emissions and
susceptibility to frequencies in the radio spectrum.
Electromagnetic compatibility is the ability of various
electronic equipment to operate properly in the intended
electromagnetic environment.

electromagnetic interference (EMI).

Waves of

electromagnetic radiation, including but not limited to
radio frequencies, generated by the flow of electric
current.

electrostatic discharge (ESD).

The flow of current

that results when objects having a static charge come
into close enough proximity to discharge.

ELP.

Extended link parameters.

ELWL.

See

extra long wavelength

EMC.