Vocab Ch. 1-4 Flashcards
computer network
An interconnection of computers and computing equipment using either wires or radio waves and can share data and computing resources.
wireless
Computer networks that use radio waves and can involve broadcast radio, microwaves, or satellite transmissions.
personal area networks
(PANs) - Networks spanning several meters around an individual. Includes devices such as laptop computers, personal digital assistants, and wireless connections.
local area networks
(LANs) - Networks spanning a room, a floor within a building, a building, or a campus.
metropolitan area networks
(MANs) - Networks that serve an area up to roughly 50km. They are high-speed networks that interconnect businesses with other businesses and the Internet.
wide area networks
(WANs) - Large networks encompassing parts of states, multiple states, countries, the world.
data
Information that has been translated into a form more conductive to storage, transmission, and calculation.
data communications
The transfer of digital or analog data using digital or analog signals.
multiplexing
The transmission of multiple signals on one medium. For a medium to transmit multiple signals simultaneously, the signals must be altered so that they do not interfere with one another.
compression
Another technique that can maximize the amount of data sent over a medium. It involves squeezing data into a smaller package, thus reducing the amount of time (as well as storage space) needed to transmit the data.
convergence
The margin of voice and data networks.
network management
The design, installation, and support of a network and its hardware and software.
workstations
Personal computers/microcomputers (desktops, laptops, netbooks, handhelds, etc.) where users reside.
servers
The computers that store network software and shared or private files.
switches
The collection points for the wires that interconnect the workstations.
routers
The connecting devices between local area networks and wide area networks. It also performs security functions and must be properly programmed to accept or reject certain types of incoming and outgoing data packets.
nodes
The computing devices that allow workstations to connect to the network and that make the decisions about where to route a piece of data.
subnetwork
Also know as a cloud, consists of the nodes and transmission lines, collected into a cohesive unit.
TCP/IP
(Transmission Control Protocol/Internet Protocol) - The language computers use to send & received data on the Internet.
client/server system
A user at a microcomputer, or client machine, issues a request for some form of data or service. The request travels across the system to a server that contains a large repository of data and/or programs. The server fills the request and returns the results to the client, displaying the results on the client’s monitor.
computer terminal
A device that was essentially a keyboard and screen with no long-term storage capabilities and little, if any, processing power.
protocol
Set of rules used by communication devices.
convergence
When different network applications and the technologies that support them converge into a single technology capable of supporting various applications.
types of convergence
1) technological
2) protocol
3) industrial
technological convergence
When two different technologies, such as the use of computers and modems to transmit data over the telephone system. Voice transmission services converged with data transmission services.
protocol convergence
When two different protocols converge to become one protocol.
industrial convergence
Where separate companies converge to provide a better service.
network architecture
Or communications model, places the appropriate network pieces in layers. The layers define a model for the functions or services that need to be preformed.
Open Systems Interconnection
(OSI) - A theoretical networking model.
TCP/IP Layers OSI Layers
TCP/IP OSI
1) application 1) Application
2) transport 2)Presentation
3) network 3) Session
4) network access 4) Transport
5) physical 5) Network
6) Data Link
7) Physical
TCP/IP - application layer
The top layer, supports the network applications and might in some cases include additional services such as encryption or compression.
Hypertext Transfer Protocol
(HTTP) - Allows Web browsers and servers to send and receive World Wide Web pages
Simple Mail Transfer Protocol
(SMTP) - Allows users to send and receive electronic mail.
File Transfer Protocol
(FTP) - Transfers files from one computer system to another.
Telnet
Allow a remote user to log in to another computer system
Simple Network Management Protocol
(SNMP) - Allows the numerous elements within a computer network to be managed from a single point.
TCP/IP - transport layer
Commonly uses TCP to maintain and error-free end-to-end connection. Includes error control-information in case one packet from a sequence of packets does not arrive at the final destination, and packet sequencing info so that all the packets stay in the proper order. It is only used at the two end points.
TCP/IP - network layer
Sometimes called the Internet layer or IP layer, is used to transfer data within and between networks.
Internet Protocol
(IP) - The software that prepares a packet of data so that it can move from one network to another on the Internet or within a set of corporate networks. Generates the network addresses necessary for the system to recognize the nest intended receiver.
TCP/IP - network access layer
Often called the data link layer - Deals with passing packets through the Internet, then it gets the data from the user workstation to the Internet.
frame
A data packet in the network access layer that contains an identifier that signals the beginning and end of the frame, as well as spaces for control information and address information.
TCP/IP - physical layer
The layer in which the actual transmission of data occurs.
OSI - application layer
Top layer, contains the application using the network.
OSI - presentation layer
Performs a series of miscellaneous functions necessary for presenting the data package properly to the sender and receiver, including encryption and decryption.
OSI - session layer
Establishes the sessions between users. It can also provide token management.
token management
A service that controls which user’s computer talks during the current session by passing a software token back and forth.
synchronization points
Backup points used in case of errors of failures.
OSI - transport layer
It ensures that the data packet that arrives at the final destination is identical to the data packet that left the originating station.
OSI - network layer
Responsible for getting the data packets from router to router through the network.
OSI - data link layer
Responsible for taking data from the network layer and transforming it into a frame.
OSI - physical layer
The bottom layer - Handles the transmission of bits over a communications channel.
logical connection
A nonphysical connection between sender and receiver that allows an exchange of commands and responses.
physical connection
The only direct connection between sender and receiver. This is where the actual 1s and 0s are transmitted over wires or airwaves.
encapsulation
The addition of control information to a packet as it moves through the layers of TCP/IP or OSI.
Modulation
The process of sending data over a signal by varying either its amplitude, frequency, or phase.
digitization
Converting analog data to digital signals.
transmitter
The originating device.
receiver
The destination device.
data
Entities that convey meaning with a computer or system.
signals
Electric and electromagnetic impulses used to encode and transmit data.
analog data & analog signals
Represented as continuous waveforms that can be at an infinite number of points between some given minimum and maximum.
noise
Unwanted electrical or electromagnetic energy that degrades the quality of signals and data.
digital data & digital signals
Composed of a discrete or fixed number of values, rather than a continuous or infinite number of values. Digital data takes the form of binary 1s and 0s.
The three basic components of digital signals
1) amplitude
2) frequency
3) phase
amplitude
The height of the wave above (or below) a given reference point.
frequency
Represented in hertz (Hz). The number of times a signal makes a complete cycle within a given time frame.
period
The length, or time interval, of one cycle. (1/frequency)
spectrum
The range of frequencies that a signal spans from minimum to maximum.
bandwidth
The absolute value of the difference between the lowest and highest frequencies.
effective bandwidth
Less than the bandwidth, it is the absolute value of the difference between lowest and highest frequencies that give the best data transmission.
phase
The position of the waveform relative to a given moment in time, or relative to time zero.
phase change
Or phase shift - Involves jumping forward (or backward) in the waveform at a given moment of time.
attenuation
The loss of power, or loss of signal strength.
Decibel (DB)
A relative measure of signal loss or gain and is used to measure the logarithmic loss or gain of a signal
amplification
The opposite attenuation - the gain of power or gain of signal strength.
modulation
The process of sending data over a signal by varying either its amplitude, frequency, or phase.
nonreturn to zero-level
(NRZ-L) Digital coding transmits 1s as zero voltages and 0s as positive voltages.
Pros: Simple and inexpensive
Cons: Long sequences of zeros in the data produce a signal that does not change, making it difficult to determine where one bit ends and the next one begins. Needs a clock.
nonreturn to zero inverted
(NRZI) Has a voltage change at the beginning of a 1 and no voltage change at the beginning of a 0.
Pros: Looks for voltage change to determine 1 or 0.
Cons: Long sequences of zeros in the data produce a signal that does not change, making it difficult to determine where one bit ends and the next one begins. Needs a clock.
Manchester encoding scheme
To transmit a 1, the signal changes from low to high in the middle of the interval, and to transmit a 0, the signal changes from high to low in the middle of the interval.
Pros: Ensures each bit has some type of signal change. Therefor, referred to as self-clocking.
Cons: Roughly half the time, there will be two transitions during each bit.