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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.
CAM. Content addressable memory.
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). A part of a computer
that includes the circuits that control the interpretation
and execution of instructions. A CPU in 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.
chassis. The metal frame in which the switch and
switch components are mounted.
circuit. An established communication path between
two ports. Consists of two virtual circuits capable of
transmitting in opposite directions. See also link.
class 1. Service that provides a dedicated connection
between two ports (also called connection-oriented
service), with notification of delivery or nondelivery.
class 2. Connectionless service between ports with
notification of delivery or nondelivery.
class 3. Connectionless service between ports without
notification of delivery. Other than notification, the
transmission and routing of class 3 frames is the same
as class 2 frames.
class F. Connectionless service for inter-switch control
traffic. Provides notification of delivery or nondelivery
between two expansion ports (E_ports).
class of service. A specified set of delivery
characteristics and attributes for frame delivery.
CLI. See command line interface.
CMI. Control message interface.
comma. A unique pattern (either 1100000 or 0011111)
used in 8b/10b encoding to specify character alignment
within a data stream. See also K28.5.
command line interface (CLI). Interface that depends
entirely on the use of commands, such as through
Telnet or simple network management protocol (SNMP),
and does not involve a graphical user interface.
community (SNMP). A relationship between a simple
network management protocol (SNMP) agent and a set
of SNMP managers that defines authentication, access
control, and proxy characteristics.
compact flash. Flash memory that stores the run-time
operating system and is used like hard disk storage. Not
visible within the memory space of the processor. Data
is stored in file system format. Also called user flash.
control processor (CP). The central processing unit
that provides all control and management functions in a
switch.
control processor card (CP card). The central
processing unit of the 2109 Model M12, which contains
two control processor (CP) card slots to provide
redundancy. Provides Ethernet, serial, and modem ports
with the corresponding light-emitting diodes (LEDs).
core switch. A switch whose main task is to
interconnect other switches. Also referred to as a
backbone switch. See also edge switch.
CP. See control processor.
CP card. See control processor card.
CPLD. Complex programmable logic device.
CPU. See central processing unit.
CRC. See cyclic redundancy check.
credit. When applied to a switch, the maximum
number of receive buffers provided by a fabric port
(F_port) or fabric loop port (FL_port) to its attached
node port (N_port) or node loop port (NL_port),
respectively, such that the N_port or NL_port can
transmit frames without over-running the F_port or
FL_port.
CSA. Canadian Standards Association.
cut-through. A switching technique that allows the
route for a frame to be selected as soon as the
destination address is received. See also route.
cyclic redundancy check (CRC). A check for
transmission errors included in every data frame.
data communications equipment (DCE) port. A port
that is capable of interfacing between a data terminal
equipment (DTE) port and a transmission circuit. DCE
devices with an RS-232 (or EIA-232) port interface
transmit on pin 3, and receive on pin 2. See also data
terminal equipment (DTE) port.
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.
57
Glossary
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