Chapter 8: Communications and Networks

communication applications

texting

email

videoconferencing 

electronic commerce 

texting

provides very efficient direct text communication between individuals using short electronic messages

email

provides a fast, efficient alternative to traditional mail by sending and receiving electronic documents 

videoconferncing 

provides an alternative to meeting in person using audio communications often with video to see the people you talk to 

electronic commerce

buying and selling goods electronically

connectivity

using computer networks to link people and resources

4 basic elements of communication systems 

sending and receiving devices 

connection devices 

data transmission specifications 

communication channel 

sending and receiving devices

often a computer or specialized communication device

originate and accept messages in form of data, information, and/or instructions

communication channels

carry data from one computer to another

cellular 

use multiple antennae/cell towers to send and receive data within relatively small geographic regions (cells)

bluetooth

short-range radio communication standard that transmits data over short distances of up to approx 33 ft

wifi wireless fidelity

high-frequency radio signals to transmit data

number of standards for wifi exist and each can send and receive data at a different speed

microwave 

uses high-frequency radio waves 

line of sight communication 

satellite communication

uses satellites as microwave relay stations

uplink

term relating to sending data to a satellite

downlink 

receiving data from a satellite 

global positioning system gps

use satellites information to uniquely determine geographic location of the device

infrared

use infrared light waves to communicate over short distances

line-of-sight communication

tv remote

twisted-pair cable 

pairs of copper wire that are twisted together 

landline telephone lines and ethernet cables 

coaxial cable

high-frequency transmission cable, single solid-copper core

over 80x transmission capacity of twisted pair

tv signals, computers

fiber-optic cable

transmits data as pulses of light through tiny tubes of glass

light, fast, more reliable

analog signals

continuous electronic waves 

telephone 

digital signals

represent presence or absence of an electronic pulse- binary

computers

modem - modulator-demodulator

communication device that translates electronic signals from a computer into electronic signals that can travel over telephone lines

modulation 

process of converting from digital to analog 

demodulation

process of converting from analog to digital

transfer rate

speed with which modems transmit data

3 types of modems 

DSL

cable

wireless 

DSL digital subscriber line

uses standard phone lines to create a high-speed connection directly to your phone company’s offices

cable modem

uses same coaxial cable as your tv

creates high-speed connections using system unit’s USB or ethernet port

wireless modem WWAN wireless wide area network modem 

almost all computers have it 

T1 lines

high-speed lines that support all digital communications, provide very high capacity, and are very expensive

T3/DS3 lines 

copper lines combined to form higher-capacity options 

optical carrier lines

provides support for very high speed, all-digital transmission for large corporations

dial-up services

antiquated method of connecting to the internet using telephones and telephone modems, which has been replaced with higher-speed connection services

cellular service providers 

support voice and data transmission to wireless devices uses cellular networks 

generations

1G- only analog signals for voice

2G- radio signals for cellular calls and texting

3G- data speeds and widespread use of internet on cell phones

4G- long term evolution LTE connections for internet speeds

5G- fast

digital subscriber line DSL service

service provided by telephone companies using existing phone lines to provide high-speed connections

ADSL asymmetric digital subscriber line 

one of the most widely used types of telephone high-speed connections (DSL)

cable service

provided by cable television companies using their existing television cables

fiber-optic service FiOS

faster speeds

requires upgraded technologies and infrastructure

satellite connection services 

use satellites to provide wireless connections 

bandwidth

measurement of width or capacity of communication channel

how much info can move across communication channel in a given amount of time

4 categories of bandwidth

voiceband/low bandwidth - landline telephone communication

medium band - special leased lines for midrange computers and mainframes

broadband - DSL, cable, satellite connections to internet

baseband - connect individual computers

protocols 

rules for exchanging data between computers 

TCP/IP transmission control protocol/internet protocol

identify sending and receiving devices

break information into small parts for transmission across internet

IP address

every computer on internet has one

packets 

before a message is sent on internet, it is broken down into small parts called packets 

computer network 

communication system that connects two or more computing devices so that they can exchange information and share resources 

node

any device connected to a network

client

node that requests and uses resources available from other nodes

server 

node that shares resources with other nodes 

directory server

specialized server that manages resources for an entire network

host

any computer system connected to a network that provides access to its resources

router 

node that forwards or routes data packets from one network to their destination in another network 

switch

central node that coordinates flow of data by sending messages directly between sender and receiver nodes

network interface cards NICs

expansion cards in system unit that connect computer to a network

network operating systems NOSs

control and coordinate activities of all computers and other devices on a network 

network administrator

computer specialist responsible for efficient network operations and implementation of new networks

local area networks 

networks with nodes in close proximity 

network gateway

device that allows one LAN to be linked to other LANS or to larger networks

home networks

allow different computers to share resources including internet

wireless LAN WLAN

uses radio frequencies to connect computers and other devices 

hotspots

wireless access points that provide internet access and are often available in public places such as coffee shops, libraries, etc

personal area network PAN

type of wireless network that works within a very small area

metropolitan area networks MANs

span distances up to 100 miles 

wide area networks WANs

countrywide and worldwide networks

network architecture

describes how a network is arranged and how resources are coordinated and shared

topology 

arrangement of a network 

bus network

topology where each device is connected to a bus/backbone

ring network

topology where each device is connected to two other devices, forming a ring

star network topology 

each device is connected directly to a central network switch 

tree network/hierarchical network

each device is connected to a central node, either directly or through one or more other devices

mesh network 

requires that each node have more than one connection to other nodes 

strategy

way of coordinating sharing of information and resources

client/server networks

use central servers to coordinate and supply services to other nodes on network

peer to peer P2P network 

nodes have equal authority and can act as both clients and servers 

intranet

private network that resembles internet

extranet

private network that connects more than one organization

firewall

hardware and software that control access to a company’s intranet and other internal networks

proxy server

computer that acts as a gateway or checkpoint in an organization’s firewall 

intrusion detection systems IDSs

work with firewalls to protect an organization’s network

virtual private networks VPNs

create a secure private connection between a remote user and an organization’s internal network