Notation Rules
Data Streaming/Storage
and the likes

2002-update, summary by J.B.Thyssen

 T1 American standard 1544 kbit/s
 E1 European standard 2048 kbit/s
 T2 American standard 6 Mbit/s (4 x T1, exotic)
 E2 European standard 8 Mbit/s (4 x E1, exotic)
 E3 European standard 34 Mbit/s (4 x E2)
 T3 American standard 45 Mbit/s (7 x T2, used a lot)
 OC-1 American standard 51 Mbit/s (SONET, verpakt 1 T3)
 E4 European standard 140 Mbit/s (4 x E3)
 OC-3 American standard 155 Mbit/s (SONET, 3 x OC-1)
 STM-1 European standard 155 Mbit/s (SDH snelheid = OC-3)
 STM-4 European standard 622 Mbit/s (4 x STM-1)
 STM-16 European standard 2488 Mbit/s (16 x STM-1; 2,5 Gbit/s)
 STM-64 European standard 9952 Mbit/s (16 x STM-1; 10 Gbit/s)

 Japanners kennen wel de T1 maar multiplexen in een andere hiërarchie
 naar 32 Mbit/s en 96 Mbit/s. Formeel zijn er geen American
 standards boven T3, in de praktijk zijn er veel proprietary
 transmissiesystemen gebouwd in de jaren tachtig tot 1,8 Gbit/s.
 In Europa zijn ook nog 565 Mbit/s (4 x E4) veelvuldig ingezet.

 SONET/SDH is midden jaren tachtig op de rails gezet
 om de wildgroei te temmen en voor de hogere snelheden
 wereldstandaarden te definiëren. In de praktijk is dat
 pas redelijk gelukt op snelheden van 155 Mbit/s en hoger
 en dan in hoofdzaak op de optische interfaces (die zijn identiek).

 De American SONET-standards volgen dezelfde hiërarchie als SDH,
 dus OC-12 = 622 Mbit/s, OC-48 = 2,5 Gbit/s, OC-192 = 10 Gbit/s

 STM-256 en/of OC-768 40 Gbit/s

 Optisch: DWDM golflengte-multiplexen
 Wordt geleverd in kanalen, per kanaal 2,5 Gbit/s of 10 Gbit/s
 16 kanalen 40 Gbit/s  (officile standard ITU)
 32 kanalen 80 Gbit/s  (Lucent Wavestar 80G)
 40 kanalen 100 Gbit/s (Ciena)
 96 kanalen 240 Gbit/s (Ciena)
 16 kanalen 160 Gbit/s
 40 kanalen 400 Gbit/s (Lucent Wavestar 400G, prototypes beschikbaar)
 128 kanalen 1,28 Tbit/s (Pirelli-TeraMux)
 160 kanalen 1,6 Tbit/s (OPTera/Nortel)



The top level of a hierarchical network. The main pipes along which
data is transferred. The "Internet backbone" is sometimes referred to, though it doesn't exist.


1. The amount of information or data that can be sent
over a network connection in a given period of time.
Bandwidth is usually stated in bits per second (bps),
kilobits per second (kbps), or megabits per second (mps).
2. The technical meaning is generalized in hacker slang.
Individuals are said to be "high bandwidth" if they are able
to process large volumes of information in short periods of time.


The speed of a modem. Specifically, the number of times per second
a communications channel changes the carrier signal it sends on the
phone line. A 2400-baud modem changes the signal 2400 times a second.

Baud is often confused with bits per second (bps).
They are technically different measurements!


Short for binary digit, the basic unit of computer storage.
All computer information is ultimately represented as bits.
Computer processing capability is evaluated by the number of bits
handled at once.
Personal computers utilize 8-, 16-, 32-, or 64-bit microprocessors.

Stands for binary digit. A bit is either on or off and is represented by "1" or "0". A collection of bits are put together to form a byte.


A bit is the smallest unit of data in a computer.
A bit has a single binary value, either 0 or 1.
Although computers usually provide instructions that can test
and manipulate bits, they generally are designed to store data
and execute instructions in bit multiples called bytes!
In most (!) computer systems, there are eight bits in a byte.
The value of a bit is usually stored as either above or below
a designated level of electrical charge in a single capacitor
within a memory device. 

bit rate

The speed of a digital transmission, measured in bits per second.

bps (bits per second)

The speed at which data bits are transmitted
over a communications medium, such as a transmission wire
or a modem. Common PC modem speeds are 28,800 and 14,400 bps.
Often expressed in thousands of bits (kilobits) per second.

Abbreviation for bits per second. A measurement of the number
of bits of information that can be sent over a network connection.


A group of 8 bits. Usually the smallest addressable unit of
information in a data memory storage unit. A single 8-bit byte
can describe 256 different binary numbers or values,
which is important in discussions of color palette,
pixel depth, and audio sample depth.
Usually each byte stores one character. 

A collection of bits to form a binary number.
The size of bytes varies from system to system.
On the original home computers, bytes were composed of 8 bits.
Now many computers operate with bytes that are 32 bits long. 

In most computer systems, a byte is a unit of information
that is eight bits long. A byte is the unit most computers use
to represent a character such as a letter, number, or typographic
symbol (for example, "g", "5", or "?"). A byte can also hold a string
of bits that need to be used in some larger unit for application
purposes (for example, the stream of bits that constitute
a visual image for a program that displays images). 


Plural of datum, a piece of information. Generally, information
of any type, but especially any information in a computer.

data rate

The amount of data or bits of information transmitted or moved
in a certain time period, usually expressed as bits or bytes
per second. In reference to .asf files, the amount of data
that must transmit in a given second for the whole file to be heard.
For a file to transmit completely and smoothly, its data rate
must be less than the bandwidth of its target network.


To transfer data from a larger "host" system to a smaller
"client" system's hard drive or other local storage device.


Ethernet is the most widely-installed local area network technology. 
Now specified in a standard, IEEE 802.3, Ethernet was originally
developed by Xerox and then developed further by Xerox, DEC, and Intel.
An Ethernet Local Area Network (LAN) typically uses coaxial cable
or special grades of twisted pair wires (TP, UTP mostly).
The previously most commonly installed Ethernet systems were called 10BASE-T
and provided transmission speeds up to 10 Mbps. Devices are connected to the cable and
compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.

Fast Ethernet 

Fast Ethernet is an upgraded standard for connecting computers
into a local area network (LAN). It works just like regular
Ethernet except that it can transfer data at a peak rate of 100 mbps.
Also referred to as 100BaseT, fast Ethernet was more expensive
and less common than its slower 10BaseT sibling.


Kilo-. Informally, 1,000. Technically, 1,024, so
64 K is actually 65,536.
Uppercase "K" is often used for kilobyte,
lowercase "k" for kilobit.

KB (kilobyte)

1,024 bytes. Approximately equivalent to
half a sheet of paper's worth of typing, double spaced.

Kb (kilobit)

1,024 bits. Also kb. 

Kbps (kilobits per second)

The common measurement of Internet bandwidth and
data transmission rates.
Refers to transmission speed of 1,024 bits per second. 

In the U.S., Kbps stands for thousands of bits per second
and is a measure of bandwidth (the amount of information
that can flow in a given time) on a data transmission medium
such as twisted-pair copper cable or coaxial cable.
On coaxial cable, bandwidth may also be in the
Mbps (millions of bits or megabits per second) range
and, on optical fiber, in the
Gbps (billions of bits or gigabits per second) range. 

Mbps (Megabits per second)

Equivalent to one million bits per second. 

Mbps stands for millions of bits per second and is a measure
of bandwidth (the total information flow over a given time)
on a data transmission medium such as twisted-pair copper cable,
coaxial cable, or optical fiber. Depending on the medium and the
transmission method, bandwidth may also be in the Kbps (thousands
of bits or kilobits per second) range or the Gbps (billions
of bits or gigabits per second) range

Megabyte (MB or MEG)

As a measure of computer processor storage and real and
virtual memory, a megabyte (abbreviated
MB) is 2 to the 20th power bytes, or
1,048,576 bytes in decimal notation. 
Not to be confused with Mb, which is used for Megabit!

modem (modulator, demodulator)

A device that you connect to your computer and to a phone line
to allow communication with other computers through the phone system.
Modems convert the computer's digital signals into analog waves
that can be transmitted over standard voice telephone lines.
Modem speeds are measured in bits per second (bps),
also sometimes expressed as kilobits (thousands of bits) per second.
In Dutch it's "de modem", not "het modem" as is often mistakenly used,
apparently they thought "the" for modem should be translated using the same
characters, and came to mistakenly write "het" instead of "de" for modem.


In 8-bit images or displays, only 256 different can be displayed
at any one time. This collection of 256 colors is called the palette.
In 8-bit environments, all screen elements must be painted with the
colors contained in the palette. The 256 color combination
is not fixedpalettes can and do change frequently.
But at any one time, only 256 colors can be used to describe
all the objects on the screen or image

pixel depth

The number of bits of color information per pixel.
On a computer monitor, each pixel may be represented
by a variable number of bits that are used to describe
the color of the pixel. Pixel depth determines how many
different colors are available. This table shows the relationship:

Pixel Depth Available Colors 
2-bit black ½ white
4-bit 16 colors 
8-bit 256 colors 
16-bit 65,356 colors 
24-bit 16,700,000+ colors 


1. The number of pixels in a file. When applied to digital video
or images, it refers to the three-dimensional measure of the frame
or image composition. Expressed as a series of three numbers, such
as 320 X 240 X 24, where the first number is the horizontal width in
pixels, the second number is the vertical height in pixels, and the
third number is the number of bits describing the color of each pixel
(pixel depth). 
1. The width and height of the video window or computer monitor display,
in pixels. Also screen resolution. 

sample depth

Bits per sample. The number of bits used to record a single sample
of audio, usually 8-bit (256 values) or 16-bit (65,536 values).
A higher sample depth results in a more accurate representation
of the original signal and higher-quality sound. Compare sample rate.

sample rate

The number of samples taken of a signal per unit time, usually
expressed as samples per second. The higher the sample rate,
the more digital sound data that is recorded, resulting in
higher-quality sound and a more accurate recording.
Typical sample rates are 8 kHz, 11 kHz, 22 kHz, and 44.1 kHz.
CD-quality audio is recorded at 44.1 kHz. Also sample frequency.
Compare sample depth. 


v. To transmit multimedia files which begin playing upon arrival
of the first packets, without needing to wait for all the data to arrive.
To send data in such a way as to simulate real-time delivery of
multimedia. The flow of streaming multimedia.
In NetShow, this stream is a common format (ASF) that can be rendered
by Microsoft Media Player. The data output by NetShow Server is a stream.
adj. streamed, streaming Files or multimedia that stream.
For example, an ASF is a streaming file containing streamed media.


A leased-line connection capable of carrying data at 1.544 Mbps,
T-1 is currently the fastest speed commonly used to connect networks
to the Internet. At maximum theoretical capacity, a T-1 line
could move a megabyte in less than 10 seconds.


A leased-line connection capable of carrying data at 44.736 Mbps,
T-3 is currently the fastest possible Internet connection.
Equivalent in bandwidth to 28 T1s. T3 is sometimes called
a 45-meg circuit.


The most common form of Ethernet is called 10BaseT,
which denotes a peak transmission speed of 10 mbps
using copper twisted-pair cable. Ethernet is a standard 
for connecting computers into a local area network (LAN).


Snelheid van datatransmissie gerekend in bytes per seconde,
huidige modems ondersteunen veelal 14k4, of 28k8, dus 14.400,
of 28.800 bits per seconde.


Representatie van 0 of 1 in de computer, kleinste rekeneenheid
voor gegevens op computers. 8 bits vormen samen 1 byte.

Bps (bytes per second)

Voor stroomsnelheden van datatransmissie wordt gerekend in bytes
per seconde aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.


Komt uit de reeks Byte, Kilobyte, Megabyte, Gigabyte.
Een Byte is acht bits voorafgegaan door een start bit
en beeindigd door een eindbit, de tussenliggende acht bits
worden gebruikt om karakters op te bouwen, of om andere gegevens
in op te slaan. Voor stroomsnelheden wordt gerekend
in bits per seconde aldus ontstaat de volgende reeks:
Bps, Kps, Mps, Gps.


Overdracht van data tussen verschillende computers.
Snelheid van communicatie wordt gemeten in bytes per seconde
en wordt ook wel baudrate genoemd.

Gb of Gigabyte

Komt uit de reeks Byte, Kilobyte, Megabyte, Gigabyte.
Een Byte is acht bits voorafgegaan door een start bit
en beeindigd door een eindbit, de tussenliggende acht bits
worden gebruikt om karakters op te bouwen, of om andere gegevens
in op te slaan. Voor stroomsnelheden wordt gerekend
in bits per seconde aldus ontstaat de volgende reeks:
Bps, Kps, Mps, Gps.

Gbs (Gigabytes per second)

Een Gb per seconde. Voor stroomsnelheden van datatransmissie,
wordt gerekend in veelvouden van bytes per seconde,
aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.

Kb of Kilobyte

Komt uit de reeks Byte, Kilobyte, Megabyte, Gigabyte.
Een Byte is acht bits voorafgegaan door een start bit
en beeindigd door een eindbit, de tussenliggende acht bits
worden gebruikt om karakters op te bouwen,
of om andere gegevens in op te slaan.
Voor stroomsnelheden wordt gerekend in bits per seconde
aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.

Kbs (Kilobyte per second)

Een Kb per seconde. Voor stroomsnelheden van datatransmissie,
wordt gerekend in veelvouden van bytes
per seconde aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.

Mb of Megabyte

Komt uit de reeks Byte, Kilobyte, Megabyte, Gigabyte.
Een Byte is acht bits voorafgegaan door een start bit
en beeindigd door een eindbit, de tussenliggende acht bits 
worden gebruikt om karakters op te bouwen, of om andere gegevens
in op te slaan. Voor stroomsnelheden wordt gerekend in bits per seconde
aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.

Een Kb per seconde. Voor stroomsnelheden van datatransmissie,
wordt gerekend in veelvouden van bytes per seconde
aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.

Mbs (Megabyte per second)

Een Kb per seconde. Voor stroomsnelheden van datatransmissie,
wordt gerekend in veelvouden van bytes per seconde
aldus ontstaat de volgende reeks: Bps, Kps, Mps, Gps.

ANSI - (American National Standard Institute). Voluntary U.S. industry association organized to develop standards.

ANSI X3T9 - Commonly referred to as FDDI. A local area network protocol that operates at 100Mbps.

Asynchronous - Having a variable time interval between successive data or information in the form of characters, operations, events. Transmission in which the data or information is individually synchronized or timed usually by start and stop bits (S/S).

ATM - Acronym for Asynchronous Transfer Mode, a high performance networking technology based on the switching of fixed length, 53 byte cells. ATM switching supports the switching of voice, video, and data; also supports isochronous communication.

Attenuation - A general term describing the loss of power between two points, measured in decibels per kilometer (dB/km) at a specified wavelength (nm).

Backbone Network - A main or high speed transmission facility or medium usually designed to connect lower speed channels or clusters of terminals. May describe common carrier main transmission path.

Bandwidth - A range of frequencies available for signaling; the differences between the highest and lowest frequencies of a band are expressed in (Hz).

BPV - Acronym for Bi-Polar Violation.

Bridge - A device used to connect two separate LANs or used to divide a large LAN into smaller LANs. Each LAN acts as its own LAN, but uses a bridge device to communicate from one LAN to another.

B-ISDN (Broadband ISDN) - A network standard from the CCITT and ANSI committee. It supports voice, data and video in the same network.

Bus - Path or channel, usually electrical, with one or more conductors, where all devices are able to receive all transmissions at the same time.

CCITT - Acronym for Consultative Committee, International Telephone and Telegraph. An international standards body responsible for setting international communications standards that allow interoperability among telephony and data communications equipment.

CD (DCD) - Acronym for Carrier Detect (Detect Carrier Detect).

CDDI - The use of unshielded or shielded twisted pair cable to transmit the FDDI signal.

CO (Central Office) - The local telephone company switch that terminates subscribers lines for switching and connecting to the public network.

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) - Access protocol for Ethernet.

Counter-Rotating Ring - Aka. Self-Healing Ring; has two physical transmission lines or rings with transmitting and receiving signals in each ring traveling in opposite directions. If the line or a device along the ring fails, the ring re-anneals by bypassing the device and or line and forms with the other ring to form a new single ring.

Crosstalk - The unwanted transfer of energy from the disturbing circuit to another called the disturbed circuit. Usually from an adjacent analog channel.

CSU - Acronym for Channel Service Unit, a device furnished as an integral part of a digital access line where a user wishes to supply the bipolar signals. It provides the network with protection against user side electrical anomalies such as surges, and provides the user with network clocking.

CTS - Acronym for Clear To Send.

DCE - Acronym for Data Communication Equipment, aka. Data Circuit-Terminating Equipment.

DCR - Acronym for Data Communication Ready.

Dispersion - The spreading of light pulses that takes place in multimode fiber optic transmission. Dispersion limits the potential transmission distance because the spread out light pulses reach the destination at different times making the signal unreadable.

DS1 - Digital Signal, Level 1 is the North American data rate used for T1 carriers. It operates at 1.544Mbps and supports 24 phone lines.

DS2 - Digital Signal, Level 2 is the North American data rate used for T2 carriers. It operates at 6.312 Mbps and supports four T1 lines or 96 phone calls

DS3 - Digital signal, Level 3 is the North American data rate used for T3 carriers. It operates at 44.736 Mbps and supports 28 T1 lines.

DSU - Acronym for Data Service Unit, a DCE used with digital communications circuits to provide digital data services interface. Located on the users premises, the DSU interfaces directly with the DTE, and provides loop equalization, remote and local test capabilities, and the logic and timing necessary to provide a standard EIA/TIA or CCITT interface. Converts signals between those used at the DTE's serial interface and bipolar signals used on the digital network. Also Network Terminal Unit (NTU).

DTE - Acronym for Data Terminating or Data Terminal Equipment.

DTR - Acronym for Data Terminal Ready.

E1 - The European standard for high speed, point to point transmission operating at 2.048 Mbps and defines 64 Kbps sub-channels.

EIA - Acronym for Electronic Industries Association. EIA, a standards body, has a set of standards which includes data communications and interface standards among others.

EMI - Acronym for Electro-Magnetic Interference.

Ethernet - Product name for one of the first popular LAN technologies, later standardized as IEEE 802.3.

FEP - Stands for Front End Processor. It is an IBM communication controller that routes traffic to and from cluster controllers.

Fiber Optic Cable - Thin filaments of glass or other transparent material sheathed in an insulator through which a light beam may be transmitted for long distances by means of multiple internal reflections. A waveguide used to transmit digital information.

FDDI - Acronym for Fiber Distributed Data Interface, is a shared medium, ring topology LAN that operates at 100 Mbps. It is ANSI standard X3T9.5, using fiber optic cable as the medium.

Flow Control - A method for a receiver to control the information flow from a transmitter. It eliminates data overflow at the receiver.

FPGA - Acronym for Field Programmable Gate Array.

Full Duplex - A communication method where both ends can transmit and receive simultaneously.

Half Duplex - A communication method where one end transmits while the other end receives, then reverses the process.

Hub - A device for local area networks (LANs) that is used to interconnect multiple devices over an internal bus.

Jitter - Aka. phase jitter, caused by power line harmonics and perceived in the form of minor phase

LAN - A local area network is a group of PCs connected over a common medium within a building.

MAC - (Medium Access Control) - A designated hardware address for each device on a LAN or MAN. This address is burnt into The network interface card (NIC) by its manufacturer.

MAN - A metropolitan area network is a group of PCs connected over a common medium within a campus environment or the same city.

Multi-Drop Line - Aka. Multipoint Line, a data link supporting multiple DTE connections, usually with one DTE controlling the link by polling the other DTEs for input and addressing output to the other DTEs. Utilizing frequency division or statistical MUX, a multipoint line can support multiple independent point-to-point channels.

Multimode fiber - An optical fiber that supports more than one propagating mode of light propagation.

Multiplexer - Aka. or Multiplexor or Mux,. A device using several communications channels at the same time, transmits and receives messages and controls communications lines, may be a microprocessor.

NA - Acronym for Numerical Aperture.

Node - A network-connected device, such as a server or PC.

OC1 - Optical Carrier Signal Level 1 refers to SONET data transmission at 51.840Mbps.

OC3 - Acronym for Optical Carrier 3, a transmission rate standard for fiber optic telephony or data communications circuits. OC3 operates at 155 Mbps speed and is part of the SONET hierarchy.

OC12 - Optical Carrier Signal Level 12 refers to SONET data transmission at 622.080Mbps.

Order Wire - Voice channel used to communicate between two locations.

OSI - (Open Data Interconnection Reference Model) - This is the International Standards Organization (ISO) model of how data communications systems can be interconnected. Communication is partitioned into seven function layers. Each layer builds on the services provided by those under it.

Packet - A grouping of data, usually consisting of data and an address header prior to being sent over a network.

PBX - Acronym for Private Branch Exchange, is a small private version of a phone company's larger central switching office.

PCM - Acronym for Pulse-Coded Modulation, a means of converting analog to digital form.

Point-of Presence (POP) - The physical access location within a specific location of the long distance or common carrier.

Polling - The method used for terminal to controller communications. The controller systematically asks for each terminal if it needs to transmit to the controller.

Protocol - A set of rules for data communication. All devices communicating together must adhere to the same rules.

RING - Path or channel; usually electrical, where devices along the path receive transmissions sequentially
from one device to the next along the ring.

Router - Similar to a bridge but provides more complex and flexible networking support. It usually also supports WANs.

RS-232 - An interface used between DTE and DCE employing serial binary data interchange, defined by EIA, aka. EIA-232. Similar to standard V.24 of CCITT.

RS-422 - Standard defined by EIA, aka. EIA-422. Deals with the electrical characteristics of balanced voltage digital interface circuits. Similar to standard V.11 of CCITT.

RS-423 - Standard defined by EIA, aka. EIA 423. Deals with electrical characteristics of unbalanced voltage digital interface circuits. Similar to standard V.10 of CCITT.

RS-449 - Standard defined by EIA, aka. EIA-449. Deals with general-purpose 37- and 9-position interface for data terminal equipment and data circuit-terminating equipment employing serial binary data interchange.

RS-485 - Standard defined by EIA, aka. EIA-485. Standard for electrical characteristics of generators and receivers for use in balanced multipoint systems.

RTS - Acronym for Request To Send.

SCADA - Acronym for Supervisory Control and Data Acquisition.

SNMP (Simple Network Management Protocol) - A standard management protocol used to provide a common means of managing network devices.

Single mode fiber - An optical fiber that supports only one mode of light propagation above the cutoff wavelength.

Synchronous Transmission - Having a constant time interval between successive bits of data or information.

SONET - Acronym for Synchronous Optical NETwork, is a hierarchical standard for a high speed (45 Mbps to 2.4 Gbps) transport network.

Star - Network in which all terminals are connected through a single point or node, such as a star coupler.

T1 - Transmission rate standard for telephony or data communications circuits. T1 operates at 1.544 Mbps speed. Usually this circuit is subdivided into many 64 Kb channels.

TCP/IP - Acronym for Transmission Control Protocol/Internet Protocol.

Time Division Multiplexing - A type of multiplexer that allocates a defined amount of backbone bandwidth for each connected device.

Time Slot - Unit of backbone bandwidth allocated for each port.

Token Ring - A LAN topology where a control packet or token is passed from station to station in sequential order. The stations wishing to access must wait for the token before transmitting data, in the token ring the next logical station is also the next physical station.

Virtual Path - A software-controlled point-to-point connection between two devices or segments.

Wide Area Network (WAN) - A computer network interconnected over distances beyond a city or metropolitan area.

802.3 - Commonly referred to as Ethernet. It is a local area network protocol that operates at 10Mbps.

802.5 - Commonly referred to as Token Ring. Operates at either 4 or 16Mbps.