ADTRAN DSU IV ESP, Руководство пользователя

Страница: 184 / 194

Appendix H. Glossary
H-4 DSU IV ESP User Manual 61204011L1-1
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.
DSU
See data service unit.
DSU loopback
A telco initiated test which loops the DSU back to the telco and is used to test the
DDS circuit as well as the DSU/CSU.
DTE
data terminal equipment. The end-user terminal or computer that plugs into the
termination point (DCE) of a communications circuit. The main difference
between the DCE and the DTE is that pins two and three are reversed.
end device
The ultimate source or destination of data flowing through a frame relay net-
work sometimes referred to as DTE. As a source device, it sends data to an inter-
face device for encapsulation in a frame relay frame. As a destination device, it
receives de-encapsulated data (i.e., the frame relay frame is stripped off, leaving
only the user's data) from the interface device.
encapsulation
A process by which an interface device places an end device's protocol-specific
frames inside a frame rely frame. The network accepts only frames formatted
specifically for frame relay; therefore interface devices acting as interfaces to a
frame relay network must perform encapsulation. See also interface device and
frame-relay-capable interface device.
file server
In the context of frame relay network supporting LAN-to-LAN communications,
a device connecting a series of workstations within a given LAN. The device per-
forms error recover and flow control functions as well as end-to-end acknowl-
edgment of data during data transfer, thereby significantly reducing overhead
within the frame relay network.