E.164 - A public
network addressing standard utilizing up to a maximum of 15 digits. ATM uses
E.164 addressing for public network addressing.
E1 - Wide-area
digital transmission scheme used predominantly in Europe that carries data at a
rate of 2.048 Mbps. E1 lines can be leased for private use from common
E3 - Wide-area
digital transmission scheme used predominantly in Europe that carries data at a
rate of 34.368 Mbps. E3 lines can be leased for private use from common
Bracing - The additional bracing required in seismic areas where
quakes or tremors are possible.
Edge Device - A
physical device which is capable of forwarding packets between legacy
interworking interfaces (e.g., Ethernet, Token Ring, etc.) and ATM interfaces
based on data-link and network layer information but which does not participate
in the running of any network layer routing protocol. An Edge Device obtains
forwarding descriptions using the route distribution protocol.
EDI (Electronic Data
Interchange) - A series of standards which provides computer to
computer data exchange over phone lines between differing computer types.
Editor - A software
program used to modify programs or files while they are being prepared or after
they are complete.
Erasable Programmable Read Only Memory)- an EPROM that can be cleared
with electrical signals rather than the traditional ultraviolet light.
EFCI (Explicit Forward
Congestion Indication) - The second bit of the payload type field in
the header of an ATM cell, the EFCI bit indicates network congestion to
receiving hosts. On a congested switch, the EFCI bit is set to "1" by the
transmitting network module when a certain number of cells have accumulated in
the network module's shared memory buffer. When a cell is received that has its
EFCI bit set to "1," the receiving host notifies the sending host, which should
then reduce its transmission rate.
Efficiency - The
ratio of output energy to input energy, expressed in percent.
Efficiency (for power
supplied) - The total output power (usually in watts) divided by the
input power with a given load. In equation form, percent efficiency at a
specified load is: % Efficiency = (output / input) 100 or 1 -(losses / input)
100 where losses, output and input are expressed in watts.
EGP (Exterior Gateway
Protocol) - Used by gateways in an internet, connecting autonomous
Egress - One of two
distinctly different roles of the MPC (Multi Protocol Client). As an Egress MPC
the client sinks or receives data frames from an Ingress MPC (Multi Protocol
egress - When
referring to a switch, fabric or port, egress typically refers to the output,
transmit or downstream side.
EIA (Electronics Industries
Association) - a USA trade organization that issues its own standards
and contributes to ANSI; developed RS-232. Membership includes USA
EISA (Extended Industry
Standard Architecture) - a bus architecture for desktop computers that
provides a 32-bit data passage while maintaining compatibility with the ISA or
ELAN (Emulated Local
Area Network) - A logical network initiated by using the mechanisms
defined by LAN Emulation. This could include ATM and legacy attached end
elarp - A Marconi
program that shows and manipulates MAC and ATM address mappings for LAN
Emulation Clients (LECs).
Applications adjust their demands in real time based on feedback about
available network bandwidth, they run "Closed Loop". Best-Effort data
applications are usually elastic (i.e. TCP, NFS, ABR). They use as much
bandwidth as they can if it is available, but less when it is unavailable.
elconfig - A
Marconi program that shows and modifies LEC configuration. Allows the user to
set the NSAP address of the LAN Emulation Configuration Server (LECS), display
the list of Emulated LANs (ELANs) configured in the LECS for this host, display
the list of ELANs locally configured along with the membership state of each,
and locally administer ELAN membership.
Non-metallic conductor of electricity in which current is carried by the
physical movement of ions.
- Force that produces or tries to produce a movement of electric charges; and
Electronic Central Office
- Modern telephone central office using solid state devices (not
electromechanical switches). Typically digital.
Electronic Voice Mail
- A system which stores messages spoken by a user, usually over a telephone,
which can be retrieved by the intended recipient when that person next calls
into the system. Also called Voice Mail, it operates just like a touch-tone
controlled answering machine.
Pertaining to electric charges at rest, with no electric current flowing.
- Region in which there is electric stress resulting from electrostatically
EM - the CellPath
300 extension module; paired with the system controller and supporting an
optional PCMCIA card.
Embedded SNMP Agent
- An SNMP agent can come in two forms: embedded or proxy. An embedded SNMP
agent is integrated into the physical hardware and software of the unit. The
CellPath 300 has an internal, integrated SNMP agent.
Interference) - signals generated and radiated by an electronic device
that cause interference with radio communications, among other effects.
End Cells - Extra
storage cells in a battery string which are switched into service to aid the
usual 23 cells if the rectifier fails temporarily, in order to maintain the
required voltage on the switching equipment (intended to extend reserve time of
End System - A
system where an ATM connection is terminated or initiated. An originating end
system initiates the ATM connection, and a terminating end system terminates
the ATM connection.
- When used in reference to an ATM network, a connection that travels through
an ATM network, passing through various ATM devices and with endpoints at the
termination of the ATM network.
End-User - The
premises occupant who uses and pays the monthly charges for the services
received, and does not resell it to others.
Energized - The
activated state of a relay or circuit.
Engine Alternator -
Generates standby AC power to sustain the essential load during commercial
power failure. The alternator may be powered by a gas turbine, diesel, or
- (1) A group of discrete alarms or status indicators emanating from the
standby power system. Outputs can be normally picked up at the engine alarm
cabinet (SD81223 01). Other connection points could be the transfer breaker
and/or engine control cabinet. (2) Major and minor visual and audible grouping
is taken from the engine alarm cabinet for automatic systems.
Enterprise - Terminology
generally referring to customers with multiple, non-contiguous geographic
Entry Border Node -
The node which receives a call over an outside link. This is the first node
within a peer group to see this call.
EPD(Early Packet discard)-
A mechanism used by some ATM switches to avoid unwanted congestion in packet
traffic. If the amount of the buffer space consumed at an outgoing port exceeds
a threshold, EPD discards new packets while packets already partially
transmitted remain unaffected.
EPROM (Erasable Programmable
Read Only Memory) - A PROM which may be erased and rewritten to
perform new or different functions (normally done with a PROM burner).
- The unit of measure for resource consumption on a link, expressed in cells
EQL (Equalization) -
The process of compensating for line distortions.
Equalizing Center -
Main discharge leads from a power plant BCB connected together on a cable rack
in the main aisle of the equipment room to a main aisle feeder. The feeder is
then tapped with leads going to a protection device to supply DC power
equipment in a line-up.
Equalizing Charge -
A routine charge applied to storage cells in an effort to equalize the voltage
across them to the same value.
Equipment Cabinet -
The cabinet or box which houses relays, circuit boards or other apparatus.
Usually also contains the power supply to convert the 120 volt AC current into
the low voltage direct current necessary to run the system.
Equipment Failure -
When a hardware fault stops the successful completion of a task.
ER (Explicit Rate)
- The Explicit Rate is an RM-cell field used to limit the source ACR to a
specific value. It is initially set by the source to a requested rate (such as
PCR). It may be subsequently reduced by any network element in the path to a
value that the element can sustain. ER is formatted as a rate.
ES (End System) - A
system in which an ATM connection is terminated or initiated. An originating
end system initiates the ATM connection, and a terminating end system
terminates the ATM connection. OAM cells may be generated and received.
ES (Errored Second)
- A second during which at least one code violation occurred.
ESF (Extended Super Frame) -
A T1 framing format that utilizes the 193rd bit as a framing bit,
but whose Superframe is made up of 24 frames instead of 12 as in D4 format. ESF
also provides CRC error detection and maintenance data link functions.
ESI (End System
Identifier) - This identifier distinguishes multiple nodes at the same
level in case the lower level peer group is partitioned.
ESN (Electronic Serial
Number) - Each cellular phone is assigned an ESN which is
automatically transmitted to the base station every time a cellular call is
placed. The Mobile Telephone Switching Office checks the ESN to make sure it is
valid, that the phone has not been reported stolen, that the users
monthly bill has been paid, etc., before permitting the call to go through.
ESS (Electronic Switching
System) - A designation for the switching equipment in Bell System
central offices. In the independent telephone company industry, the
abbreviation is EAX.
Essential AC Load -
A load that must operate during prolonged loss of commercial power. It must be
connected to the standby power source and be able to tolerate an interruption
of ten seconds or more.
ETACS (Extended TACS)
- The conventional cellular technology used in the United Kingdom and other
countries. It is developed from the U.S. AMPS technology.
Ethernet - A
10-Mbps, coaxial standard for LANs in which all nodes connect to the cable
where they contend for access.
Exception - A
connectivity advertisement in a PNNI complex node representation that
represents something other than the default node representation.
Excessive Zeroes (EXZ) Error
Event - An Excessive Zeroes error event for an AMI-coded signal is the
occurrence of more than fifteen contiguous zeroes. For a B8ZS coded signal, the
defect occurs when more than seven contiguous zeroes are detected.
Exchange - (1) A
room or building equipped so that telephone lines terminating there may be
interconnected as required; and (2) switching exchange: an aggregate of
traffic-carrying devices, switching stages, controlling and signaling means at
a network node that enables subscriber lines and/or other telecommunication
circuits to be interconnected as required by individual callers.
Exterior - Denotes
that an item (e.g., link, node, or reachable address) is outside of a PNNI
Exterior Link - A
link that crosses the boundary of the PNNI routing domain. The PNNI protocol
does not run over an exterior link.
Exterior Reachable Address
- An address that can be reached through a PNNI routing domain, but which is
not located in that PNNI routing domain.
Exterior Route - A
route that traverses an exterior link.
External Alarms -
General description given to alarms which are then transferred from central
office to a remote surveillance center.