communications and networks chp 8
transfer rate
the speed at which modems transmit data, typically measured in bits per second (bps).
Videoconferencing
provides a very-low-cost alternative to long-distance telephone calls using electronic voice and video delivery.
Mesh network
A topology requiring each node to have more than one connection to the other nodes so that if a path between two nodes is disrupted, data can be automatically rerouted around the failure using another path.
telephone lines
A transmission medium for both voice and data.
wireless access point
AKA base station, interprets incoming radio frequencies and routes communications to the appropriate devices.
Voiceband
AKA low bandwidth; used for standard telephone communication. Personal computers with telephone modems and dial-up service use this bandwidth. While effective for transmitting text documents, it is too slow for many types of transmission, including high-quality audio and video.
proxy server
All communications between the company's internal networks and the outside world pass through this server. decides whether it is safe to let a particular message or file pass into or out of the organization's network.
Fiber-optic service (FiOS)
An Internet connection service that is not yet widely available. Current providers of FiOS include Google and Verizon with speeds faster than cable or DSL connections.
cell towers
Antennae that support cellular communication.
dial-up services
Antiquated method of connecting to the Internet using telephones and telephone modems, which has been replaced with higher-speed connection services.
Twisted-pair cable
Cable consisting of pairs of copper wire that are twisted together.
Satellite connection services
Connection services that use satellites and the air to download or send data to users at a rate seven times faster than dial-up connections.
Wide area networks (WANs)
Countrywide and worldwide networks that use microwave relays and satellites to reach users over long distances.
Global positioning system (GPS)
Devices that use location information to determine the geographic location of your car, for example.
Texting
provides very efficient direct text communication between individuals using short electronic messages.
Packetization
Information sent or transmitted across the Internet usually travels through numerous interconnected networks.Before the message is sent, it is reformatted or broken down into small parts called packets
local area networks (LANs)
Network consisting of computers and other devices that are physically near each other, such as within the same building.
ADSL (asymmetric digital subscriber line)
One of the most widely used types of telephone high-speed connections (DSL).
PAN
Personal area network; connects digital devices such as PDAs
Modulation
Process of converting digital signals to analog signals.
Demodulation
Process performed by a modem in converting analog signals to digital signals.
DSL (digital subscriber line)
Provides high-speed connection using existing telephone lines.
modem
Short for modulator-demodulator. It is a communication device that translates the electronic signals from a computer into electronic signals that can travel over telephone lines.
analog signals
Signals that represent a range of frequencies, such as the human voice. They are a continuous electronic wave signal as opposed to a digital signal that is either on or off.
Cellular service providers
Supports voice and data transmission to wireless devices.
WiMax (Worldwide Interoperability for Microwave Access)
Technology that extends Wi-Fi networks to operate over greater distances.
Communication channels
are an essential element of every communication system. These channels actually carry the data from one computer to another.
hub
The center or central node for other nodes. This device can be a server or a connection point for cables from other nodes.
topology
The configuration of a network. The five principal network topologies are ring, bus, star, tree, and mesh.
cells
The space created by the intersection of a vertical column and a horizontal row within a worksheet in a program like Microsoft Excel.
(megabits) per second (Mbps)
The transfer rate of millions of bits per second.
IP address (Internet protocol address)
The unique numeric address of a computer on the Internet that facilitates the delivery of e-mail.
Satellite
This type of communication uses satellites orbiting about 22,000 miles above the earth as microwave relay stations.
Downlink
To receive data from a satellite.
Uplink
To send data to a satellite.
Ethernet cables
Twisted-pair cable commonly used in networks and to connect a variety of components to the system unit.
cable modem
Type of modem that uses coaxial cable to create high-speed computer connections.
Cellular
Type of wireless connection that uses multiple antennae (cell towers) to send and receive data within relatively small geographic regions (cells).
hotspot
Wireless access points that provide Internet access and are often available in public places such as coffee shops, libraries, bookstores, colleges, and universities.
computer network
a communication system that connects two or more computers so that they can exchange information and share resources.
Network administrator
a computer specialist responsible for efficient network operations and implementation of new networks.
Connectivity
a concept related to using computer networks to link people and resources.
network gateway
a device that allows one LAN to be linked to other LANs or to larger networks.
Coaxial cable
a high-frequency transmission cable, replaces the multiple wires of telephone lines with a single solid-copper core.
Bandwidth
a measurement of the width or capacity of the communication channel. Effectively, it means how much information can move across the communication channel in a given amount of time.
Router
a node that forwards or routes data packets from one network to their destination in another network.
Client
a node that requests and uses resources available from other nodes. Typically a user's personal computer
Server
a node that shares resources with other nodes.
extranet
a private network that connects more than one organization.
intranet
a private network within an organization that resembles the Internet.
Bluetooth
a short-range radio communication standard that transmits data over short distances of up to approximately 33 feet. widely used for wireless headsets, printer connections, and handheld devices.
Directory Server
a specialized server that manages resources, such as user accounts, for an entire network.
personal area network (PAN)
a type of wireless network that works within a very small area—your immediate surroundings.
Connection devices
act as an interface between the sending and receiving devices and the communication channel. They convert outgoing messages into packets that can travel across the communication channel.
wireless modem
also known as a WWAN (wireless wide area network) modem; Typically a small plug-in USB or ExpressCard device that provides very portable high-speed connectivity from virtually anywhere.
hierarchical network
another name for tree network
Host
any computer system connected to a network that provides access to its resources.
Node
any device that is connected to a network. It could be a computer, printer, or data storage device.
affect how data is transmitted
bandwidth and protocols
Electronic commerce
buying and selling goods electronically.
Switch
central node that coordinates the flow of data by sending messages directly between sender and receiver nodes.
Microwave
communication uses high-frequency radio waves.
firewall
consists of hardware and software that control access to a company's intranet and other internal networks.
Network operating systems (NOS)
control and coordinate the activities of all computers and other devices on a network. These activities include electronic communication and the sharing of information and resources.
domain name server (DNS)
converts text-based addresses to IP addresses.
Virtual private networks (VPN)
create a secure private connection between a remote user and an organization's internal network.create the equivalent of a dedicated line between a user's home or laptop computer and a company server.
Network architecture
describes how a network is arranged and how resources are coordinated and shared. It encompasses a variety of different network specifics, including network topologies and strategies.
Wireless connections
do not use a solid substance to connect sending and receiving devices. Rather, they move data through the air.
Star network
each device is connected directly to a central network switch. Whenever a node sends a message, it is routed to the switch, which then passes the message along to the intended recipient.
Tree network
each device is connected to a central node, either directly or through one or more other devices. The central node is connected to two or more subordinate nodes that in turn are connected to other subordinate nodes, and so forth, forming a treelike structure.
Bus network
each device is connected to a common cable called a bus or backbone and all communications travel along this bus.
Ring network
each device is connected to two other devices, forming a ring; When a message is sent, it is passed around the ring until it reaches the intended destination.
Communication Systems
electronic systems that transmit data from one location to another.
TCP/IP (transmission control protocol/Internet protocol)
essential features of this protocol involve (1) identifying sending and receiving devices Page 203 and (2) breaking information into small parts, or packets, for transmission across the Internet.
Network interface cards (NIC)
expansion cards located within the system unit that connect the computer to a network. Sometimes referred to as a LAN adapter.
Home
local area network for home and apartment use, typically wireless
LAN
local area network, located within close proximity
networks
may be citywide and even international, using both cable and wireless connections. Local area, metropolitan area, and wide area networks are distinguished by the size of the geographic area they serve.
MAN
metropolitan area network; typically spans cities with coverage up to 100 miles
peer-to-peer (P2P) network
nodes have equal authority and can act as both clients and servers. The most common way to share games, movies, and music over the Internet
Sending and receiving devices
often a computer or specialized communication device. They originate (send) as well as accept (receive) messages in the form of data, information, and/or instructions.
Cable service
provided by cable television companies using their existing television cables. These connections are usually faster than DSL.
Digital subscriber line (DSL) service
provided by telephone companies using existing telephone lines to provide high-speed connections.
provides a fast, efficient alternative to traditional mail by sending and receiving electronic documents.
digital signals
represent the presence or absence of an electronic pulse—the on/off binary signals
Data transmission specifications.
rules and procedures that coordinate the sending and receiving devices by precisely defining how the message will be sent across the communication channel.
Protocols
rules for exchanging data between computers
packets
sent separately over the Internet, possibly traveling different routes to one common destination.
Metropolitan area networks (MAN)
span distances up to 100 miles. These networks are frequently used as links between office buildings that are located throughout a city.
First-generation mobile telecommunications (1G)
started in the 1980s using analog radio signals to provide analog voice transmission service.
Second-generation mobile telecommunications (2G)
started in the 1990s using digital radio signals.
Third-generation mobile telecommunications (3G)
started in the 2000s and provided services capable of effective connectivity to the Internet, marking the beginning of smartphones.
Communication channel
the actual connecting or transmission medium that carries the message. This medium can be a physical wire or cable, or it can be wireless.
computer communications
the process of sharing data, programs, and information between two or more computers.
Fiber-optic cable
transmits data as pulses of light through tiny tubes of glass.
how many categories of communication channels
two
Client/server networks
use central servers to coordinate and supply services to other nodes on the network. The server provides access to resources such as web pages, databases, application software, and hardware.
Medium band
used in special leased lines to connect midrange computers and mainframes as well as to transmit data over long distances. This bandwidth is capable of very-high-speed data transfer.
Wi-Fi (wireless fidelity)
uses high-frequency radio signals to transmit data.
infrared
uses infrared light waves to communicate over short distances.
wireless LAN (WLAN)
uses radio frequencies to connect computers and other devices.
strategy
way of coordinating the sharing of information and resources.
WAN
wide area network for countrywide or worldwide coverage
Broadband
widely used for DSL, cable, and satellite connections to the Internet.
Baseband
widely used to connect individual computers that are located close to one another. Like broadband, it is able to support high-speed transmission. can only carry a single signal at a time.
hypertext transfer protocol secure
widely used to protect the transfer of sensitive information.
WLAN
wireless local area network; all communication passes through an access point
Intrusion detection systems (IDS)
work with firewalls to protect an organization's network. These systems use sophisticated statistical techniques to analyze all incoming and outgoing network traffic.