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Appendix D. Glossary
61200659L1-1 MX2800 STS-1 User Manual D-5
DCE
Data communications equipment. Device that provides all the functions required
for connection to telephone company lines and for converting signals between
telephone lines and DTE. Also see DTE.
DDS
Digital data service. A private line digital service for transmitting data
end-to-end at speeds of 2.4, 4.8, 9.6, and 56 kbps (and in some cases 19.2, 38.4,
or 64 kbps). The systems can use central hub offices for obtaining test access,
bridging legs of multi-point circuits, and cross connecting equipment. DDS is
offered on an inter-LATA (local access and transport area) basis by AT&T and on
an intra-LATA basis by the Bell operating companies.
delay
The amount of time by which a signal is delayed. A round-trip transmission
delay measurement helps detect possible causes of protocol timeouts.
DLCI
Datalink communications identifier. A unique number assigned to a PVC end-
point in a frame relay network. Identifies a particular PVC endpoint within a
user's access channel in a frame relay network and has local significance only to
that channel.
DS1
Digital signal level one. Twenty-four DS0 channels make up one DS1 (total
bandwidth is 1.544 Mbps).
DS3
Digital signal level three. Equivalent of 28 DS1s and 672 DS0s (total bandwidth
is 44.736 Mbps).
DSR
Data set ready. A signal on the DTE interface that indicates if a connection exists
and if the devices are ready to start handshaking control signals so communica-
tions can begin.