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Glossary glo-3
Composite
is the input/output port of a local multiplexer, that transmits and receives the multi-
plexed voice and data from a remote multiplexer.
Concentrator
is a communications device that allows a shared transmission medium to accom-
modate more data sources than there are channels available.
Configuration database
see “Database.”
Congestion
is a local condition that occurs when there are too many packets to be queued in the
node buffers, causing information transfer to be delayed.
D
Database
contains the files that define network configuration, subscribers, alarms and statistics.
Datagram
is the basic unit of information passed across the Internet. It is the IP equivalent of a
packet.
DCE
stands for “data circuit-terminating equipment,” which provides the functions nec-
essary for communication operations between the end-user device (see “DTE”) and
the network. “Physical DCE” refers to the hardware configuration, and “Logical
DCE” refers to the software configuration. Note that physical and logical DCE are
independent of each other; however, for each, if one end of the connection is DCE, the
other must be DTE, and vice versa.
Designated Bridge, Designated Port
is the bridge (and the SmartSwitch 1800 port on the bridge) on a LAN that provides
the minimum-cost path to the root bridge (described later).
Dial Port
is an X.25 port connected to a dialup modem.
Dotted Decimal Notation
is the syntactic representation for a 32-bit integer consisting of four 8-bit numbers (in
base 10) separated by periods. This format is used for IP addresses.
DSAP
stands for “destination service access point,” which is the address of the link service
access point (LSAP) to which a link protocol data unit (LPDU) is sent.
DSU
stands for Data Service Unit, which interfaces between Data Terminal Equipment and
a digital data service.