User`s guide

Glossary G-7
G
ESF (Extended Superframe Format)
A new T1 framing standard used in Wide Area Networks (WANs). With this
format 24 frames, instead of 12 are grouped together. ESF provides frame
synchronization, cyclic redundancy checking and data link bits in overhead. It
allows more information to be stored and retrieved easily, facilitating network
performance monitoring and maintenance.
F
failed signal state
Occurs when ten consecutive severely errored seconds are detected.
far end
The unit or units remote from the user.
FE (Framing Errors)
Occurs when the end of a frame is not detected where it should be.
FDL (Facility Data Link)
A four Kbps data channel provided by 12 of the 24 ESF framing bits. It is used
by the carrier to request reports, clear error counters and activate loop backs.
FG (Frame Ground)
A signal from DTE to DSU/CSU.
fractional bandwidth DTE loopback
A loopback test that loops back the signal at the network interface.
See also
loopback.
Fractional T1
A service that provides less than full T1 capacity (one or more 64 Kbps
channels are provided).
frame
A group of bits sent serially over a communications channel. The basic data
transmission unit employed with bit oriented protocols.
frame relay
A high-speed packet switching protocol used for wide area networks (WANs);
faster than traditional X.25 networks, because it was designed for today's
reliable circuits and performs less rigorous error detection. Frame relay networks
use bandwidth only when there is trafÞc to send. Frame relay does not support
voice.
framing
A technique which separates incoming bits into identiÞable groups to enable
the receiving device to recognize and reconstruct them.