|Network Terms Glossary:
The physical gateway between a customer's local loop and the frame relay
A device used to boost the strength of an electronic or optical signal,
which is weakened (attenuated) as it passes through the transport
network. Amplifiers add gain to the signal by an amount equal to the
loss in the previous section of the network since last amplification.
Asymmetric Digital Subscriber Line (ADSL)
A new technology that allows more data to be sent over existing copper
telephone lines. ADSL supports data rates of from 1.5 to 9 Mbps when
receiving data (known as the downstream rate) and from 16 to 640 Kbps
when sending data (known as the upstream rate).
Asynchronous Transfer Mode (ATM)
A method of sending audio, visual and computer data at the same time
over one high-speed digital line.
Atlantic Crossing (AC-1)
Part of the Global Crossing network. AC-1 links the United States,
United Kingdom, Netherlands and Germany. It became operational in May
Capacity on terrestrial fiber optic cables from undersea cable landing
stations to metropolitan areas.
A range of frequencies between two defined limits.
A measure of capacity of information-carrying capacity on a
communications channel. Narrowband: Less than or equal to 64 Kbps.
Wideband: Digital rates between 64 Kbps and 1.544 Mbps (DSI) or 2.048
Mbps (E1)-LANs, bulk files transfer, video conferencing, and multimedia.
Broadband: Greater than 44.736 Mbps (D3) or 34.368 Mbps (E3).
Bidirectional Line Switched Ring (BLSR)
Commonly referred to as BLSR. It is a method of SONET transport in which
half of the working network is sent counterclockwise over one fiber and
the other half is sent clockwise over another fiber. BLSR offers
bandwidth use advantages for distributed traffic in single-ring
A binary unit of information that can have either of two values, 0 or 1.
Contraction of binary digit: kilobit = 1,000 bits; megabit = 1 million
bits; gigabit = 1 billion bits; terabit = 1 trillion bits.
Border Gateway Protocol (BGP)
A routing protocol used in interdomain routing in large networks to
maintain integrity of the network. It allows the routers to exchange
only prespecified information with prespecified routers in other
A data communications device that connects two or more network segments
and forwards packets between them. It also amplifies the carrier signal,
and accepts data packets, (perhaps buffering them during periods of
network congestion) and forwards them.
A transmission channel usually carrying a tremendous amount of
information at transmission speeds of 45 Mbps (45,000,000 bits per
second) or greater. A communications channel with a bandwidth
sufficiently large to carry voice, data and video on a signal channel.
Any voice communications channel having a bandwidth greater than a
A way of doing data transmission, usually faster than normal
transmission mode, in which a continuous block is transferred between
main memory and an input/output device without interruption until the
transfer has been completed. Characteristically, burst mode is
sustainable for only limited periods of time under special conditions.
The information-carrying ability of a telecommunications system, as
defined by its design (number of fibers, system length, and
optoelectronic equipment) and its deployed equipment (amount of
optoelectronics in the station) and measured in bits per second.
Capacity is sold in discrete units, usually system interface levels such
as DS-3s and STM-1s, that in the aggregate are the equivalent of total
A third-party provider of communications services by wire, fiber or
radio. Common Carrier: A private company offering facilities or services
to the general public on a non-discriminatory basis and regulated as to
market entry, practices, and rates by various Federal and State
authorities. Private Carrier: Services provided for internal use and
free of most common carrier regulations to allow discrimination in
service provision or pricing.
Challenge-Handshake Authentication Protocol
An authentication method that can be used when connecting to an Internet
Service Provider. CHAP allows you to log in to your provider
automatically, without the need for a terminal screen.
The process of subdividing the bandwidth of a circuit into smaller
increments called channels. Typically, each channel carries an
individual transmission, e.g., a voice conversation, a data
conversation, or a computer-to-computer session. This process is
accomplished through a multiplexer, such as dense wavelength division
Algorithm that minimizes the redundancy in the signal to be transmitted.
The process of concealing the contents of a message from all except
those who know the key. Cryptography is used to protect e-mail messages,
credit card information, and corporate data. As the Internet and other
forms of electronic communication become more prevalent, electronic
security is also becoming increasingly important.
Refers to a virtual channel in a fiber optic system utilizing DWDM. Each
virtual channel is supported through a specific wavelength of light,
with many channels riding over the same fiber. Once the fiber system is
deployed and the DWDM equipment is activated, some of the wavelengths
may be activated immediately and others may be left dark for future
needs. When the need arises, those dark wavelengths are lit up.
Dense Wavelength Division Multiplexing (DWDM)
A technique which employs more than one light source and detector
operating at different wavelengths and simultaneously transmits optical
signals through the same fiber while message integrity of each signal is
Describes a method of storing, processing and transmitting information
through the use of distinct electronic or optic pulses representing the
binary digits 0 and 1. In communications they will modify a carrier at a
selected frequency. The precise signal transitions preclude any
distortion such as graininess or snow in the case of video transmission,
or static or other background distortion in the case of audio
Method of storing, processing and transmitting information through the
use of distinct electronic or optical pulses that represent the binary
digits 0 and 1. Digital transmission and switching technologies employ a
sequence of these pulses to represent information as opposed to a
continuously variable analog signal. The precise digital numbers
preclude any distortion such as graininess or snow in the case of video
transmission, or static or other background distortion in the case of
Various impurities may be added to silica-based fiber optic strands as
they are constructed to achieve specifically desired transmission or
A digital transmission hierarchy supporting 1.544 million bits per
second that may be used for "near-full motion" or compressed video, data
or voice circuits (24, 48, or 96).
Similar to the North American T-1, E-1 is the European format for
digital transmission. E-1 carries signals at 2.048 Mbps (32 channels at
64 Kbps), versus the T-1, which carries signals at 1.544 Mbps (24
channels at 64 Kbps). E-1 and T-1 lines may be interconnected for
Erbium-Doped Fiber Amplifier (EDFA)
A purely optical (as opposed to electronic) device used to boost an
optical signal. It contains several meters of glass fiber doped with
erbium ions. When the erbium ions are excited to a high energy state,
the doped fiber changes from a passive medium to an active amplifying
The ability of a system to respond gracefully to an unexpected hardware
or software failure. There are many levels of fault tolerance, the
lowest being the ability to continue operation in the event of a power
The number of route kilometers installed multiplied by the number of
fiber strands along the path.
Technology based on thin filaments of glass or other transparent
materials used as the medium for transmitting coded light pulses that
represent data, image and sound. Fiber-optic technology offers extremely
fast transmission speeds.
The simultaneous transmission of data in both directions, used when
communicating between two computers. Full duplex is sometimes called
"Echo On" by some communications programs.
Gbps (Gigabits per second)
A data rate of 1 Gbps corresponds to 1,000 million bits per second.
High Performance Parallel Interface (HIPPI)
HIPPI is used to network supercomputers, high-end workstations and
peripherals using cross-bar type circuit switches. It provides for
transfer rates of 800 Mbps over 32 twisted pair copper wires (single
HIPPI) and 1,600 Mbps over 64 pairs (double HIPPI).
Indefeasible Right of Use (IRU)
A measure of currency in the undersea cable business. The owner of an
IRU has the right to use the capacity for the time and bandwidth to
which the IRU applies.
International Telecommunication Union (ITU)
The ITU is an intergovernmental agency of the United Nations within
which the public and private sectors cooperate for the development of
telecommunications. The ITU adopts international regulations governing
the use of the radio spectrum and develops standards to facilitate the
interconnection of telecommunications systems on a worldwide basis. It
is headquartered in Geneva, Switzerland. In 1996, the ITU comprised 185
Member States and 363 members (scientific and industrial companies,
public and private operators, broadcasters, regional and international
organizations active in three sectors: Radio communications,
Standardization and Development).
A fabric of interconnected computer networks, originally known as the
DARPA network (Defense Advanced Research Projects Agency) connecting
government and academic sites. It currently links about 50 million
people worldwide who use it for everything from scientific research to
Internet Protocol (IP) Address
An Internet address that is a unique number consisting of four parts
separated by dots, sometimes called a "dotted quad." For example,
18.104.22.168. Every Internet computer has an IP address and most
computers also are assigned one or more domain names that are easier to
remember than the dotted quad.
Internet Service Provider.
The 11th letter of the Greek alphabet. Lambda is used as the symbol for
wavelength in lightwave systems. Fiber optic systems use multiple
wavelengths of light through dense wavelength division multiplexing
(DWDM). Each range of wavelength appears in a "window" roughly
corresponding to a color in the visible light spectrum.
The amount of time it takes a packet to travel from source to
destination. Together, latency and bandwidth define the speed and
capacity of a network.
The physical facility, leased from a local exchange carrier (LEC), which
provides connectivity between the customer's location and the carrier's
point of presence.
Low Voltage Differential Signaling (LVDS)
A low noise, low power, low amplitude method for high-speed (gigabits
per second) data transmission over copper wire.
Media Gateway Control Protocol (MGCP)
A proposed control and signal standard for the conversion of audio
signals carried on telephone circuits to data packets carried over the
Internet or other packet networks. Unlike regular phones, IP phones and
devices are not fixed to a specific switch, so they must contain
processors that enable them to function independently from a central
switching location. MGCP eliminates the need for complex,
processor-intense IP telephony devices, thus simplifying and lowering
the cost of these terminals.
Megabits per second (Mbps)
One Mbps corresponds to a data rate of 1,000,000 bits per second.
The ability of one network node to send identical data to a number of
end servers on the multicast backbone. For large amounts of data, IP
multicasting is more efficient than normal Internet transmissions
because the server can broadcast a message to multiple recipients
Multilink Point-to-Point Protocol (MP)
MP allows multiple physical connections between two points to be
combined into a single logical connection called a bundle. MP supports
dynamic bandwidth allocation, which means that physical links can be
added or removed from the bundle as needed.
The electronic conversation between two or more people or groups of
people in different places using two or more types of digitally
integrated communication for voice, sound, text, data, graphics, video,
image or presence at the same time. Applications include conferencing,
presentations, training, referencing, games, etc.
An electronic or optical process that combines two or more lower
bandwidth transmissions onto one higher bandwidth signal by splitting
the total available bandwidth into narrower bands (frequency division)
or by allotting a common channel to several transmitting sources one at
a time in sequence (time division).
Pertaining or referring to a communications line to which three or more
stations are connected. It implies that the line physically extends from
one station to another until all are connected.
MultiProtocol Label Switching (MPLS)
MPLS is a widely supported method of speeding up data communication over
combined IP/ATM networks. This improves the speed of packet processing
and enhances performance of the network.
Thin filaments of glass through which light beams are transmitted.
Enormous capacity, low-cost, low-power consumption, small space,
lightweight, insensitivity to electromagnetic interference characterize
this transport media.
Generic term for a bundle of data, organized in a specific way for
transmission. A packet consists of the data to be transmitted and
certain control information, including the destination address.
A process where messages are broken into finite-sized packets that are
always accepted by the network. The message packets are sent across
different circuit paths. The packets are reassembled into the original
message at the end of the circuit.
In networking, pipelining is a technique used at the transport layer or
data link layer in a layered network architecture that allows for the
transmission of multiple frames without waiting to see if they are
acknowledged on an individuals basis.
Point of Presence (POP)
The physical location within a LATA where an interexchange carrier's
circuits interconnect with the local lines of telephone companies in
Making continuous requests for data from another device. For example,
modems that support polling can call another system and request data.
Computer rules that provide uniform specifications so that computer
hardware and operating systems can communicate.
1. Equipment that receives a low-power signal, possibly converting it
from light to electrical form, amplifying it or retiming and
reconstructing it for transmission. It may need to be reconverted to
light for retransmission. 2. An optoelectrical device used at each end
and occasionally intermediate points of exceptionally long fiber optic
span. Optical input is converted to electrical form to restore a clean
signal, which drives lasers that fully restores the optical signal at
the original signal strength.
Requests for Comments (RFCs)
Internet standards that have developed within the Internet community
since 1969. They have grown to become a large series of numbered
Internet informational documents and standards widely followed by
commercial software and freeware in the Internet and Unix communities.
Few RFCs are standards but all Internet standards are recorded in RFCs.
Perhaps the single most influential RFC has been RFC 822, the Internet
electronic-mail format standard. RFCs are unusual in that they are
floated by technical experts acting on their own initiative and reviewed
by the Internet at large, rather than formally promulgated through an
institution such as ANSI (American National Standards Institute). For
this reason, they remain known as RFCs even after they have been adopted
A network device that connects two similar networks having the same
network protocol. It also chooses the best path between two networks
when there are multiple paths.
RFS (Ready for Service)
The data of provisional acceptance or commercial service of a cable
Serial Line Internet Protocol (SLIP)
An Internet protocol which is used to run IP over serial lines such as
telephone circuits. It allows a packet to traverse multiple networks on
the way to its final destination.
The largest standard circuit unit of capacity, which consists of 155,500
Kbps (equal to 155 Mbps). Thus, each Gbps contains enough capacity for
6.4 STM-1 circuits. While capacity is sold to the largest
telecommunications companies in minimum investment units equal to one
STM-1 unit, most telecommunications companies buy smaller units at a
price higher than the equivalent STM-1 price.
Synchronous Transfer Mode (STM)
New term for traditional TDM switching to distinguish it from ATM.
Time Division Multiplex (TDM)
A technique for transmitting a number of separate data, voice and/or
video signals simultaneously over one communications medium by quickly
interleaving a piece of each signal one after another.
Voice over IP (VoIP)
VoIP is voice communications transmitted over the Internet.
The distance between two crests of a signal or a carrier and is measured
in terms of meters, millimeters, nanometers, etc. In lightwave
applications, because of the extremely high frequencies, wavelength is
measured in nanometers.
Wavelength Division Multiplexing (WDM)
A way of increasing the information-carrying capacity of an optical
fiber by simultaneously operating at more than one wavelength. With WDM
you can multiplex signals by transmitting them at different wavelengths
through the same fiber.
A term referring to a variety of new Digital Subscriber Line
technologies. Some of these varieties are asymmetric with different data
rates in the downstream and upstream directions. Others are symmetric.
Downstream speeds range from 384 Kbps (or "SDSL") to 1.5-8 Mbps (or