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Access
Port:
The physical gateway between a customer's local loop and the
frame relay network.
Asymmetric Digital Subscriber Line or 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).
Amplifier:
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.
ATM
(Asynchronous Transfer Mode):
A method of sending audio, visual and computer data at the
same time over one high-speed digital line.
Backhaul
Capacity:
Capacity on terrestrial fiber optic cables from undersea cable
landing stations to metropolitan areas.
Band:
A range of frequencies between two defined limits.
Bandwidth:
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).
BGP or Border Gateway Protocol:
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 domains.
Bidirectional
Line Switched Ring:
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 architectures.
Bit:
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
Bridge:
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.
Broadband:
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 voice grade channel.
Burst
Mode:
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.
Capacity:
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-3's and STM-1's, that in the aggregate
are the equivalent of total system capacity.
Carrier:
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.
Channelization:
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
or a data conversation – a computer-to-computer session. This
process is accomplished through a multiplexer, such as dense
wavelength division multiplexers.
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.
Compression:
Algorithm that minimizes the redundancy in the signal to be
transmitted.
Cryptography:
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.
Dark
Wavelength:
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.
Digital:
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 transmission.
Digital
Transmission:
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 audio
transmission.
Doped
Fibers:
Various impurities may be added to silica-based fiber optic
strands as they are constructed to achieve specifically desired
transmission or physical properties. Erbium-Doped Optical
Fiber Amplifier (EDFA) optical amplifiers use a section of
optical fiber doped with the rare earth erbium and optically
pumped with a laser diode. It can amplify a range of wavelengths
at the same time surrounding a base wavelength of 1550 nm.
Praseodymium-doped fibers produce a signal gain of 30 dB in
1310 nm fibers.
DSI:
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).
DWDM
(Dense Wavelength Division Multiplexing):
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 preserved.
E-1:
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 64Kbps), versus the T-1, which carries signals
at 1.544 Mbps (24 channels at 64Kbps). E-1 and T-1 lines may
be interconnected for international use.
EDFA
(Erbium-Doped Fiber Amplifier):
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 medium.
Fault
Tolerance:
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 failure.
Fiber
Kilometers:
The
number of route kilometers installed multiplied by the number
of fiber strands along the path.
Fiber
Optics:
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.
Full
Duplex:
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
Level Data Link Control or HDLC:
A generic link layer protocol standard for point-to-point
and multi-point communications that is bit oriented and in
which control codes differ according to their bit positions
and patterns.
High
Performance Parallel Interface or 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 megabits a second over 32 twisted pair copper
wires (single HIPPI) and 1600 megabits a second over 64 pairs
(double HIPPI).
Internet:
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 simple E-Mail.
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, 198.204.112.1. 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.
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.
ISP:
Internet Service Provider.
ITU
(International Telecommunications Union): 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).
Lambda:
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.
Latency:
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.
Local
Loop:
The physical facility, leased from a LEC, which provides connectivity
between the customer's location and the carrier's point of
presence.
Low
Voltage Differential Signaling or LVDS:
A low noise, low power, low amplitude method for high-speed
(gigabits per second) data transmission over copper wire.
Mbps
(Megabit per second):
One Mbps corresponds to a data rate of 1,000,000 bits per
second.
Media
Distribution Centers or MDCs:
MDCs are part of GlobalCenter's digital distribution architecture
which bypasses the congested Internet infrastructure to provide
enhanced performance. GlobalCenter's standard MDC facilities
are equipped with state-of-the-art technology and provide
the highest levels of security and fault tolerance for our
customer's servers.
Media
Gateway Control protocol or 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.
Multicasting:
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 simultaneously.
Multilink
Point-to-Point Protocol or 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.
Multimedia:
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.
Multiplexing:
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).
Multipoint:
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 or 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.
Optical Fiber:
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.
PTTs
(Post, Telephone and Telegraph companies):
International telecommunications carriers which are generally
under the control of the government in a country that has
not yet privatized its telecommunication markets.
Packet:
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.
Packet
Switching:
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.
Pipelining:
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 that LATA. Polling Making continuous requests
for data from another device. For example, modems that support
polling can call another system and request data.
Protocols:
Computer rules that provide uniform specifications so that
computer hardware and operating systems can communicate.
Repeater:
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:
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 as standards.
Route
Kilometers:
The number of route kilometers installed.
Router:
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 system.
STM
(Synchronous TransferMode):
New term for traditional TDM switching to distinguish it from
ATM.
STM-1:
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.
Serial
Line Internet Protocol or 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.
Time
Division Multiplex or 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.
VoIP:
VoIP stands for "voice over IP," which is voice communications
transmitted over the Internet.
Wavelength:
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 or 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.
xDSL:
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 "ADSL").
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