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

216 Glossary
Glossary
typeahead A facility that allows
terminal users to enter data
before a read is actually posted to
the terminal.
UPS See uninterruptible
power supply.
unacknowledged frame
number (K) The number of
frames that can be transmitted
without receiving an
acknowledgment from the
destination address. When this
number (K) frame is reached, the
same K frames are retransmitted.
unedited mode See
transparent mode.
uninterruptible power
supply A hardware device that
protects equipment from power
failures and contains an internal
storage battery to supply reserve
power.
V.24 The CCITT recommendation
that defines the function of the
interchange circuits between a
DTE and a DCE.
validation The process of
ascertainingwhetherthenetwork
transport configuration file has
been correctly configured. In
guided NMMGR, you do this by
pressing the Validate Netxport
key.
VAN Value-Added Network. A
datacommunicationnetworkthat
uses and pays for facilities
belonging to another carrier. The
value-added package is then sold
to a user.
VC See virtual circuit.
virtual circuit A logical
association between two
physically separate DTEs.
Virtual Terminal A network
service that allows a user to
establish interactive sessions on a
node.
VPLUS Software used to
generate screens such as those
displayed by NMMGR.
V-Series (V.##) CCITT A set of
CCITT recommendations related
to data communication over a
voice-grade telephone network.
VT See Virtual Terminal.
Workstation Configurator A
utility (TTUTIL) that allows
users to create customized
terminal and printer types by
entering data through a series of
VPLUS screens.
X.3 Defines the user facilities
that should be internationally
available from the packet
assembler/disassembler (PAD)
facility when this is offered by a
public data network.
X.21 Defines the physical
interface between a DTE and a
DCE of a public data network
where the access to the network
is made over synchronous digital
lines.