Specifications

Data
Information represented in digital form, including voice, text,
facsimile and video.
Data Link Layer
Layer 2 of the OSI model. The entity, which establishes, maintains,
and releases data-link connections between elements in a network.
Layer 2 is concerned with the transmission of units of information,
or frames, and associated error checking.
Diagnostics
The detection and isolation of a malfunction or mistake in a
communications device, network or system.
Digital
The binary (“1” or “0”) output of a computer or terminal. In data
communications, an alternating, non-continuous (pulsating) signal.
E3
The European standard for high speed digital transmission, operating
at 34 Mbps.
Encapsulation
Encapsulating data is a technique used by layered protocols in which
a low level protocol accepts a message from a higher level protocol,
then places it in the data portion of the lower-level frame. The
logistics of encapsulation require that packets traveling over a
physical network contain a sequence of headers.
Ethernet
A local area network (LAN) technology which has extended into the
wide area networks. Ethernet operates at many speeds, including
data rates of 10 Mbps (Ethernet), 100 Mbps (Fast Ethernet), 1,000
Mbps (Gigabit Ethernet), 10 Gbps, 40 Gbps, and 100 Gbps.
Flow Control
A congestion control mechanism that results in an ATM system
implementing flow control.
Frame
A logical grouping of information sent as a link-layer unit over a
transmission medium. The terms packet, datagram, segment, and
message are also used to describe logical information groupings.
Framing
At the physical and data link layers of the OSI model, bits are fit into
units called frames. Frames contain source and destination
information, flags to designate the start and end of the frame, plus
information about the integrity of the frame. All other information,
such as network protocols and the actual payload of data, is
encapsulated in a packet, which is encapsulated in the frame.
Full Duplex
A circuit or device permitting transmission in two directions (sending
and receiving) at the same time.
FXO (Foreign
Exchange Office)
A voice interface, emulating a PBX extension, as it appears to the CO
(Central Office) for connecting a PBX extension to a multiplexer.
FXS (Foreign
Exchange Subscriber)
A voice interface, emulating the extension interface of a PBX (or
subscriber interface of a CO) for connecting a regular telephone set
to a multiplexer.
G.703
An ITU standard for the physical and electrical characteristics of
various digital interfaces, including those at 64 kbps and 2.048
Mbps.