Configuring and Managing Host-Based X.25 Links - Edition 5 (36939-90054)

Glossary 191
Glossary
block mode Terminalprocessing
mode in whichgroups, or “blocks,”
of data are transmitted all at
once.
BNC T-Connector Connector
used to connect a computer or a
component such as a DTC to the
LAN in a ThinLAN configuration.
boundary See network
boundary.
bps Bits per second. The number
of bits passing a point per second.
broadcast Communication
method of sending a message to
all devices on a link
simultaneously.
byte A sequence of eight
consecutive bits operated on as a
unit.
call In X.25, a call is an attempt
to set up communication between
two DTEs using a virtual circuit.
Also known as a virtual call.
call collision A conflict that
occurs at a DTE/DCE interface
when there is a simultaneous
attempt by the DTE and DCE to
set up a call using the same
logical channel identifier.
called address When a node
sends out a call request packet,
the packet contains the address of
the destination node. The address
of the destination node is the
called address.
calling address When a node
receives an incoming call packet,
the packet contains the address of
the sending node. The address of
the sending node is the calling
address.
carrier A continuous wave that
is modulated by an information
bearing signal.
catenet See internetwork.
CCITT Consultative Committee
for International Telephony and
Telegraphy. An international
organization of communication
carriers, especially government
telephonemonopolies,responsible
for developing telecommunication
standards by making
recommendations. No carrier is
required to adhere to a CCITT
recommendation, although most
do so in their own interest.
CIB The channel input/output
bus in the backplane of an
HP 3000.
circuit-switching network A
type of data communications
network wherein a physical and
exclusive link is maintained
between two communicating
devices for the call duration. An
all-digital, circuit-switching
network is often referred to as an
X.21 network.
closed user group An X.25 user
facility that allows
communication to and from a
pre-specified group of users and
no one else.