IBM 2109 Model M12 User Manual page 81

gateway. Hardware that connects incompatible
networks by providing the necessary translation for both
hardware and software.
GBIC. See gigabit interface converter.
Gbps. Gigabits per second.
GBps. Gigabytes per second.
generic port (G_port). A generic port that can operate
as either an expansion port (E_port) or a fabric port
(F_port). A port is defined as a G_port when it is not yet
connected or has not yet assumed a specific function in
the fabric.
gigabit interface converter (GBIC). A removable
serial transceiver module designed to provide gigabaud
capability for fibre channel (FC) and other products that
use the same physical layer.
gigabit switch. A 16-port, Fibre Channel gigabit
switch.
G_port. See generic port.
half duplex. A mode of communication that allows a
port to either transmit or receive frames at any time, but
not simultaneously (with the exception of link control
frames, which can be transmitted at any time). See also
full duplex.
hard address. The arbitrated loop physical address
(AL_PA) that a node loop port (NL_port) attempts to
acquire during loop initialization.
hardware translative mode. Method for achieving
address translation. The two hardware translative
modes that are available to a QuickLoop-enabled switch
are standard translative mode and QuickLoop mode.
See also standard translative mode and QuickLoop
mode.
HBA. See host bus adapter.
heartbeat. Through clustering software, the application
server continually communicates with the clustered
spare using network heartbeats to indicate to the other
machines that everything is operating correctly. This
heartbeat is typically carried over a dedicated network
for clustering traffic. In cases of a problem (for example,
a software crash on the operational server or a
hardware component failure), a heartbeat link indicates
to the other server that something has failed or is
otherwise inoperative. If that heartbeat is lost, the spare
server takes over the function provided by the
application service. Depending on the clustering
software, either the entire server or only specific
services on the server can be failed over or failed back.
high availability. An attribute of the switch that
identifies it as being capable of operating well in excess
of 99 percent of the time. High availability is typically
identified by the number of nines in that percentage. For
example, a switch that is rated at five nines would be
capable of operating 99.999 percent of the time without
failure.
high port count fabric. A fabric containing 100 or
more ports.
host bus adapter (HBA). The interface card between
a server or workstation bus and the Fibre Channel
network.
hot pluggable. A field replaceable unit (FRU)
capability that indicates it can be extracted or installed
while customer data is otherwise flowing in the chassis.
hub. A Fibre Channel wiring concentrator that
collapses a loop topology into a physical star topology.
Nodes are automatically added to the loop when active
and removed when inactive.
IC bus. A serial, 2-wire bus used to monitor field
replaceable unit (FRU) temperatures and control the
system including blade power control.
ID. Identification.
IDB. Interface descriptor block.
IDLE. Continuous transmission of an ordered set over
a Fibre Channel link when no data is being transmitted,
to keep the link active and maintain bit, byte, and word
synchronization.
IEC. International Electrotechnical Commission.
IETF. Internet Engineering Task Force.
information unit (IU). A set of information as defined
by either upper-level process protocol definition or
upper-lever protocol mapping.
initiator. A server or workstation on a Fibre Channel
network that initiates communications with storage
devices. See also target.
in-order delivery (IOD). A parameter that, when set,
guarantees that frames are either delivered in order or
dropped.
integrated fabric. The fabric created by six switches
cabled together and configured to handle traffic as a
seamless group.
Internet protocol (IP). In the Internet suite of
protocols, a connectionless protocol that routes data
through a network or interconnected networks and acts
as an intermediary between the higher protocol layers
and the physical network.
inter-switch link (ISL). A Fibre Channel link that
connects two switches (a link from the expansion port
(E_port) of one switch to the E_port of another).
61
Glossary