User's Manual

FT-512 Trailblazer Installation and User Manual version 1.08 50
command or a response.
CRC
cyclic redundancy check. A computational means to ensure the accuracy of
frames transmitted between devices in a frame relay network. The mathematical
function is computed, before the frame is transmitted, at the originating device.
Its numerical value is computed based on the content of the frame. This value is
compared with a recomputed value of the function at the destination device.
CS
See CTS.
CSU
See channel service unit.
CTS
clear to send. A signal on the DTE interface indicating that the DCE is clear to
send data.
DBU
dial backup. Providing a secondary, switched dial service to route data upon
primary link failure.
data service unit
DSU. A device designed to transmit and receive digital data on digital transmission
facilities.
dB
decibel. A unit of measure of signal strength, usually the relation between a
transmitted signal and a standard signal source.
data communications equipment (DCE)
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
multipoint circuits, and cross connecting equipment. DDS is offered on an inter-
LATA basis by AT&T and on an inter-LATA basis by the Bell operating companies.
data link connection identifier (DLCI)
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.
discard eligibility (DE)
A user-set bit indicating that a frame may be discarded in preference to other
frames if congestion occurs, to maintain the committed quality of service within
the network. Frames with the DE bit set are considered Be excess data.
DSR
data set ready. A signal on the EIA-232 interface that indicates if the
communications is connected and ready to start handshaking control signals so
communications can begin.
DSU