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Technical Glossary
Index
ANSI | ATM | bandwidth
| bit | BRI | byte
| convergence | DS1 | DS3 | DSL | FDDI | Frame Relay | Gbps | GUI
| IP | IP telephony |ISDN | Kbps | Mbps
| MBps | MegaBit | MegaByte | OC-x | POTS
| PRI | SONET | T1
| T3 | telco | telephony
| VoIP
ANSI
Acronym for the American National Standards Institute.
Founded in 1918, ANSI is a voluntary organization composed of over 1,300 members
(including all the large computer companies) that creates standards for a
wide range of technical areas, from electrical specifications to
communications protocols, including the computer industry.
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ATM
ATM, (Asynchronous Transfer Mode) or "fast
packet," is a means of digital communications that is capable of very
high speeds; suitable for transmission of images or voice or video as well as
data
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Bandwidth
The carrying capacity of a given
information transmission circuit, system or network. A circuit or network
capable of carrying large amounts of information is said to have 'high
bandwidth' whereas a circuit or network capable of carrying only a small
amount of information is said to have 'low bandwidth.
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Bit
Short for binary digit, the smallest unit of information on a
machine. The term was first used in 1946 by John Tukey, a leading
statistician and adviser to five presidents. A single bit can hold only one
of two values: 0 or 1. More meaningful information is obtained by combining
consecutive bits into larger units. For example, a byte is composed of 8
consecutive bits.
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BRI
Short for Basic Rate Interface, the basic ISDN configuration,
which consists of two B-channels that can carry voice or data at rate of
64Kbps, and one D-channel, which carries call-control information. Another
type of ISDN configuration is called Primary-Rate Interface (PRI), which
consists of 23 B-channels (30 in Europe) and
one D-channel.
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Byte
Abbreviation for binary term, a unit of storage capable of
holding a single character. A byte is equal to 8 bits. Large amounts of memory
are indicated in terms of kilobytes (1,024 bytes), megabytes (1,048,576
bytes), and gigabytes (1,073,741,824 bytes).
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Convergence
The concept that modern information
technologies, currently based on very disparate technological designs and
systems, are becoming digital in nature. At present a person might receive
information by telephone, television, radio, newspaper and print. In the
future these different information delivery systems may be replaced by a
unified system based wholly on digital technology.
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DS1
A DS1 is a High Capacity Special Access Service that will provide you with
high-speed, dedicated, point-to-point facilities capable of transmitting
multiple streams of information. Also see T-1.
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DS3
A DS3 is similar to a DS1 with a bandwidth of 43 Mbps, a channelized DS3 has
the ability to carry 28 DS1s (at a cost lower than just ordering 28 DS1s).
Also see T-3.
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DSL
Refers collectively to all types of Digital Subscriber Lines,
the two main categories being ADSL and SDSL. Two other types of xDSL
technologies are High-data-rate DSL (HDSL) and Symmetric DSL (SDSL). xDSL is similar to ISDN however, xDSL
offers much higher speeds - up to 32 Mbps when receiving data (known as the
downstream rate), and from 32 Kbps to over 1 Mbps when sending data (known as
the upstream rate). ADSL
(Asymmetric DSL), 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 for downstream traffic and from 16 to 640 Kbps for upstream traffic.
SDSL (Symmetric DSL), a new technology that allows more data to be
sent over existing copper telephone lines (POTS). SDSL supports data rates up
to 3 Mbps. SDSL is called symmetric because it supports the same data rates
for upstream and downstream traffic. SDSL can operate simultaneously with
voice connections over the same wires.
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FDDI
Abbreviation of Fiber Distributed Data Interface,
a set of ANSI protocols for sending digital data over fiber optic cable. FDDI
networks are token-passing networks, and support data rates of up to 100 Mbps
(100 million bits) per second. FDDI networks are typically used as backbones
for wide-area networks.
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Frame Relay
A packet-switching protocol for connecting devices on a Wide Area Network
(WAN). Frame Relay networks in the U.S. support data transfer rates at
T-1 (1.544 Mbps) and T-3 (45 Mbps) speeds. In fact, you can think of Frame
Relay as a way of utilizing existing T-1 and T-3 lines owned by a service
provider. Most telephone companies now provide Frame Relay service for
customers who want connections at 56 Kbps to T-1 speeds.
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Gbps
Short for Gigabits per second, a data transfer
speed measurement for high-speed networks such as Gigabit Ethernet. When used
to describe data transfer rates, a gigabit equals 1,000,000,000 bits.
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GUI
(Graphical User Interface)
A technology for interacting with a
computer that involves pictorial (graphical and visual) representations of
information such as windows, icons and so on. Apple's MacOS and Microsoft's
Windows are the two most popular computer GUIs. Pronounced 'gooey.
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IP
(Internet Protocol)
IP specifies the format of packets and
the addressing scheme. Most networks combine IP with a higher-level protocol
called Transport Control Protocol (TCP), which establishes a virtual
connection between a destination and a source. IP by itself is something like
the postal system. It allows you to address a package and drop it in the
system, but there’s no direct link between you and the recipient. TCP/IP, on
the other hand, establishes a connection between two hosts so that they can
send messages back and forth for a period of time.
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IP Telephony
See definition of VoIP.
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ISDN
Integrated Services Digital Network, a set of
communications standards allowing a single wire or optical fiber to carry
voice, digital network services and video. ISDN is intended to eventually replace
the plain old telephone system. There are different kinds of ISDN connection
of varying bandwidth.
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Kbps
kilobits per second; 1,024 bits for technical
purposes, such as data storage. 1,000 for general purposes. Data transfer
rates are measured in kilobits per second, abbreviated as Kbps, and count a
kilo as 1,000 bits.
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Mbps
Short for megabits per second, a measure of data
transfer speed. Networks, for example, are generally measured in Mbps.
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MBps
Short for MegaBytes per second, a measure of data
transfer speed. Mass storage devices are generally measured in MBps.
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MegaBit
(1) When used to describe data storage, 1,024 kilobits.
(2) When used to describe data transfer rates, it refers to one million bits.
Networks are often measured in megabits per second, abbreviated as Mbps.
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MegaByte
(1) When used to describe data storage, 1,048,576 bytes. Megabyte is
frequently abbreviated as M or MB.
(2) When used to describe data transfer rates, as in MBps, it refers to one
million bytes.
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OC-x
Short for Optical Carrier, used to specify the speed of fiber
optic networks conforming to the SONET standard. The table shows the speeds
for common OC levels.
OC-1 = 51.84 Mbps
OC-3 = 155.52 Mbps
OC-12 = 622.08 Mbps
OC-24 = 1.244 Gbps
OC-48 = 2.488 Gbps
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POTS
Short for plain old telephone service, which
refers to the standard telephone service that most homes use. In contrast,
telephone services based on high-speed, digital communications lines, such as
ISDN and FDDI, are not POTS. The main distinctions between POTS and non-POTS
services are speed and bandwidth. POTS is generally restricted to about 52
Kbps (52,000 bits per second). The POTS network is also called the public
switched telephone network (PSTN).
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PRI
Primary Rate Interface, a type of ISDN service designed
for larger organizations. PRI includes 23 B-channels (30 in Europe)
and one D-Channel. In contrast, BRI (Basic Rate Interface), which is designed
for individuals and small businesses, contains just two B-channels and one
D-channel. PRI service is generally transmitted through a T-1 line.
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SONET
Short for Synchronous Optical Network, a standard for
connecting fiber-optic transmission systems. SONET was proposed by Bellcore in
the middle 1980s and is now an ANSI standard. SONET defines interface
standards at the physical layer of the OSI seven-layer model. The standard
defines a hierarchy of interface rates that allow data streams at different
rates to be multiplexed. SONET establishes Optical Carrier (OC) levels from
51.8 Mbps (about the same as a T-3 line) to 2.48 Gbps. Prior rate standards
used by different countries specified rates that were not compatible for
multiplexing. With the implementation of SONET, communication carriers
throughout the world can interconnect their existing digital carrier and
fiber optic systems.
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T-1
A dedicated phone connection supporting data rates of 1.544Mbits per second.
A T-1 line actually consists of 24 individual channels, each of which
supports 64Kbits per second. Each 64Kbit/second channel can be configured to
carry voice or data traffic. Most telephone companies allow you to buy just
some of these individual channels, known as fractional T-1 access. T-1 lines
are sometimes referred to as DS1 lines.
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Telco
Contraction of “telephone
company”. Provider of
telecommunications services.
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Telephony
Generally, voice-oriented communications
technology as a whole. Pronounced te·leph·o·ny (t -l f  -n )
emphasizing the second syllable, not the third
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T-3
A dedicated phone connection supporting data rates of about 43 Mbps. A T-3 line
actually consists of 672 individual channels, each of which supports 64 Kbps.
T-3 lines are sometimes referred to as DS3 lines. One T-3 has 28 times the
bandwidth of one T-1.
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VoIP (Voice over Internet Protocol)
Also called Internet or IP telephony.
VoIP is the two-way transmission of phone conversations over an IP network,
allowing audio to travel over the Internet, intranets, or private LANs (local
area networks) and WANs (wide area networks). A main
advantage of VoIP is that users can connect from anywhere and make phone
calls without incurring typical analog telephone charges, such as for
long-distance calls.
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