Chapter
9 - Communications and Networks
Communications
What is computer communications?
°
A process in
which one computer transfers data, instructions, and information to another
computer(s)
What is needed for successful
communications?
What
is the primary function of a communications device?
°
To convert or
format signals so they are suitable for the communications channel or a
receiving device
Sending and Receiving Devices
What is a sending and receiving
device?
°
Initiates or
accepts transmission of data, instructions, and information
What
are some specialized sending and receiving devices?
Uses of Communications Technologies
What are some uses of
communications technology?
°
Communications
technology use is all around you
What is voice mail?
°
Allows callers to
leave a voice message for the called party
°
Unlike answering
machines, voice mail converts an analog voice message into digital form
°
The message is
stored in a voice mailbox
°
A voice mailbox
is a storage location on a computer in the voice mail system
What is fax?
°
A document
transmitted and received over telephone lines
°
Can contain
handwritten or typed text, illustrations, photographs, or other graphics
°
You can send or
receive a fax using a stand-alone fax machine or a computer fax modem
What is e-mail (electronic mail)?
°
The exchange of
text messages and computer files transmitted via a communications network
°
To send and
receive e-mail messages, you use e-mail software installed on your computer
What is instant messaging (IM)?
°
A real-time
Internet communications service that notifies you when one or more people are
online and then allows you to exchange messages or files with them or join a
private chat room
What is a chat room?
°
Permits users to
converse in real time with each other via the computer while connected to the
Internet
°
Types of chat
rooms
•
Voice chats
•
Video chats
•
Radio chats
What is a newsgroup?
°
An area on the
Web where users conduct written discussions about a particular subject
°
Also called a
threaded discussion
°
The difference
between a chat room and a newsgroup is that a chat room is a live conversation,
and the newsgroup is not
What is Internet telephony?
°
Enables you to
talk to other people over the Internet
°
Uses the Internet
to connect a calling party and one or more called parties
°
You need Internet
telephone software
°
Speak into a a
computer microphone
°
Internet
telephone software and your computer’s sound card digitize and
compress your
conversation and then
transmit the digitized
audio
What is videoconferencing?
°
Involves using
video and computer technology to conduct a meeting between participants at two
or more geographically separate locations
°
Requires
computers with
microphones,
speakers, video
cameras, and
communications
devices and
software
What are other conferencing systems?
°
Web conference
•
Conferencing
system that uses the Internet, Web browsers, and Web servers to deliver this
service
°
Video telephone
call
•
Used by home
users to see
each other as
they talk on
the Internet
What is collaboration?
°
Working with
other users connected to a server
°
You can conduct
online meetings
•
Allows you to
share
documents
with others in
real time
°
You also can
collaborate via
e-mail
°
Microsoft’s
NetMeeting allows
collaboration
What is groupware?
°
A software
application that helps groups of people work together on projects and share
information over a network
°
A component of
workgroup computing
•
includes network
hardware and software that enables group members to work together
°
Most groupware
provides personal information manager (PIM) functions
What is a global positioning system (GPS)?
°
Consists of one
or more earth-based receivers that accept and analyze signals sent by
satellites in order to determine the receiver’s geographic location
What is Digital Angel™?
°
A computer chip
containing a GPS device
°
Worn as a
bracelet or woven into fabric that has an antenna that communicates with the
GPS satellite
°
Measures and
sends biological information to the satellite
Networks
What is a network?
°
A collection of
computers and devices connected by communications channels
°
Facilitates
communications among users and allows users to share resources with other users
What is a site license?
°
A legal agreement
that allows multiple users to run a software package simultaneously
°
License fee
usually is based on the number of users or the number of computers attached of
the network
What
is a local area network (LAN)?
°
A network that
connects computers and devices in a limited geographical area such as a home,
school computer laboratory, office building, or closely positioned group of
buildings
What is a node ?
°
Each computer or
device on a network
What is a network operating system?
°
The system
software that organizes and coordinates the activities on a local area network
°
Also called a
network OS or NOS
How do some popular operating
systems support networks ?
°
Many operating
systems have built-in network features
°
In other cases,
the network OS is a set of programs that works with another operating system(s)
What is a peer-to-peer LAN?
°
A simple,
inexpensive network that typically connects less than 10 computers together
°
Each computer on
a peer-to-peer network can share the hardware, data, or information located on
any other computer in the network
°
Each computer stores
files on its own storage devices
What is a client/server LAN?
°
A network in
which one or more computers act as a server and the other computers on the
network can request services from the server
What are servers and clients?
°
Server
• Controls access to the hardware and software on
the network
• Provides a centralized storage area for programs
• Dedicated servers perform a specific task
Company on the Cutting Edge
°
One of the
leading personal computer makers
°
Second-largest
computer seller
°
Initial success
came from marketing IBM clones,
look-alike computers
that performed like
the IBMs, but were
less costly
Networks
What is a wide area network (WAN)?
°
A network that
covers a large geographic area using a communications channel that combines
many types of media
°
Can be one large
network or can consist of two or more LANs connected together
°
The Internet is
the world’s largest WAN
What is an Internet use of
peer-to-peer (P2P)?
°
An Internet
network that enables users with the same networking software to connect to each
other’s hard disks and exchange files directly
°
Napster and
Gnutella are two examples of P2P
What is a metropolitan area network
(MAN)?
°
A backbone
network that connects local area networks in a metropolitan area such as a city
or town
°
Handles the bulk
of communications activity, or traffic, across that region
What is a network topology?
°
The
configuration, or physical arrangement, of the devices in a communications
network
°
Networks usually
use combinations of three topologies
What is a bus network?
°
Consists of a
single central cable, to which all computers and other devices connect
°
The bus is the
physical cable
°
The bus is also
called the backbone
°
Inexpensive and
easy to install
What is a ring network?
°
A cable forms a
closed ring, or loop, with all computers and devices arranged along the ring
°
Data travels from
device to device around the entire ring, in one direction
°
If a device
fails, all the devices before the failed device are unaffected, but those after
the failed device cannot function
What is a star network?
°
All of the
devices connect to a central computer
°
The central
computer is called the hub
°
All data that
transfers from one computer to another passes through the hub
What are network communications
technologies?
°
Specific
combinations of hardware and software that allow the different devices on
several types of networks to be able to communicate
Technology Trailblazer
Robert Metcalfe
°
The inventor of
Ethernet
°
Founder of 3Com
Corporation
°
Former publisher
and a current InfoWorld magazine columnist
°
He realizes the
need for computer professionals to communicate their ideas clearly when they
speak and write
Company on the Cutting Edge
°
Started in 1982
by Scott McNealy and three friends
°
Goal of building
engineering workstations in the network computer model
°
The
fastest-growing company in history based on revenue and the world’s second most
profitable company
°
Builds the
technology to power the Internet
Networks
What is Ethernet?
°
A LAN technology
that allows personal computers to contend for access to the network
°
Based on a bus
topology, but can be wired in a star pattern
°
The most popular
LAN because it is relatively inexpensive and easy to install and maintain
What is token ring?
°
A LAN technology
that controls access to the network by requiring that network devices share or
pass a special signal, called a token
°
A token is
similar to a ticket
°
The device with
the token
can transmit data over
the network
°
Only one token
exists
per network
°
Based on a ring
topology,
although it can use
a star topology
What is TCP/IP?
°
Short for
transmission control protocol/Internet protocol
°
A technology that
manages the transmission of data by breaking it up into packets
°
Commonly used for
Internet transmissions
What
is the Wireless Applications Protocol (WAP)?
°
Allows wireless
mobile devices to access the Internet and its services such as the Web and
e-mail
°
Uses a
client/server network
°
The wireless
device contains
the client software, which
connects to the Internet
service provider's
server
°
Devices that
support
WAP are called
WAP-enabled devices
What is an intranet?
°
An internal
network that uses Internet technologies
°
Generally makes
company information accessible to employees and facilitate working in groups
°
Typically also
includes a connection to the Internet
What is an extranet?
°
Allows customers
or suppliers to access part of a company’s intranet
What is a firewall?
°
A general term
that refers to hardware and/or software that restricts access to data and
information on a network
What is a home network?
°
Multiple
computers connected together in a home or home office
°
All computers in
the
house can
• connect to the
Internet at the
same time
• access files
and programs
on the other
computers in
the home
• share
peripherals
What are four types of home
networks?
What is an intelligent home network?
°
Extends the basic
home network to include features such as lighting control, thermostat
adjustment, and a security system
Communications Software
What is communications software?
°
Consists of
programs that help you establish a connection to another computer or network
°
Manages the
transmission of
data, instructions, and
information
°
For two computers
to
communicate, they must
have compatible
communications
software
°
Often, separate
communications programs
on your computer each serve
a different purpose
What is the Internet Connection Wizard?
°
A type of
communications software that helps you establish a connection to another
computer on the Internet using wizards, dialog boxes, and other on-screen
messages
How
do you access the Internet?
°
Enter a user name
and password into a communications software dialog box to connect to an ISP
What is file transfer protocol (FTP)?
°
An Internet
standard that allows you to upload and download files to and from a Web server,
called the FTP server
°
An anonymous FTP
site allows anyone to transfer files
°
Other sites
require a specific username and password to access the FTP server
The Telephone Network
What
is the public switched telephone network (PSTN)?
°
The worldwide
telephone system that handles voice-oriented telephone calls
What is a dial-up line?
°
A temporary
connection that uses one or more analog telephone lines for communications
°
Not permanent
°
A modem at the
sending end dials the telephone number of a modem at the receiving end
What is a dedicated line?
°
A connection that
always is established between two communications devices
°
The quality and
consistency of the connection is better than a dial-up line because dedicated
lines provide a constant connection
What is transfer rate?
°
The speed with
which a line carries data and information
°
The faster the
transfer rate, the faster you can send and receive data and information
°
Usually are
expressed as bits per second (bps)
What
are popular types of digital dedicated lines?
°
ISDN
°
DSL
°
T-carrier
°
ATM
What is an ISDN line?
°
Integrated
Services Digital Network
°
A set of
standards for digital transmission of data over standard copper telephone lines
°
Telephone line
can carry three or more signals at once, through the same line using a
technique called multiplexing
What is DSL?
°
Digital
subscriber line
°
Transmits at fast
speeds on existing standard copper telephone wiring
°
Some
installations can be used for both voice and data
°
Requires a
special network card or DSL modem
°
ADSL (asymmetric
digital subscriber line) supports faster transfer rates when receiving data
than when sending data
What is a T-carrier line?
°
Any of several
types of digital lines that carry multiple signals over a single communications
line
°
Uses a technique
called multiplexing so that multiple signals can share the telephone line
°
Provides
extremely fast data transfer rates
°
Usually only
affordable by medium to large companies
What is asynchronous transfer mode (ATM)?
°
A service that
carries voice, data, video, and multimedia at extremely high speeds
°
Predicted to
become the Internet standard for data transmission
Communications Devices
What is a communications device?
°
Any type of
hardware capable of transmitting data, instructions, and information between a
sending device and a receiving device
°
Sometimes the
device must convert the data, instructions, and information from analog to
digital signals or vice versa
What is a modem?
°
A communications
device that converts a computer's digital signals to analog signals before they
are transmitted over standard telephone lines
°
Sometimes called
a dial-up modem
What are internal and external modems?
°
external modem
•
a stand-alone
(separate) device
•
attaches to a
special serial
port on a computer
•
a standard
telephone cord
connects to a telephone outlet
°
Internal modem
•
A card that you
insert into an expansion slot on a computer's motherboard
•
A standard
telephone cord attaches between a port on the modem
and the telephone outlet
What is a digital modem?
°
One that sends
and receives data and information to and from a digital telephone line such as
ISDN or DSL
What is a cable modem?
°
A modem that
sends and receives data over the cable television (CATV) network
°
Currently much
faster than a
dial-up modem
or ISDN
°
Usually attaches
to a USB port or
a port on a
network interface
card
What is a network interface card (NIC)?
°
Also called a LAN
adapter
°
A card you insert
into an expansion slot of a personal computer or other device, enabling the
device to connect to a network
°
Works with a
particular network technology
°
Available for
desktop and mobile computers
What is a hub?
°
A device that
provides a central point for cables in a network
Communications Channel
What is a channel?
°
The
communications path between two devices
What is a typical communications channel?
What are characteristics of transmission
media?
Physical Transmission Media
What is physical transmission media?
°
Wire, cable, and
other tangible (touchable) materials used to send communications signals
What is twisted-pair cable?
°
Consists of one
or more twisted pair wires bundled together
°
Each twisted pair
wire consists of
two separate
insulated copper
wires
°
Twisted together
to reduce noise
°
Noise is an
electrical
disturbance that
can degrade
communications
What is coaxial cable?
°
Consists of a
single copper wire surrounded by at least three layers
°
Often called
coax
°
Often used
for cable
television
wiring
What is fiber-optic cable?
°
Contains a core
of dozens or hundreds of thin strands of glass or plastic
°
Uses light to
transmit signals
°
Each strand
is called an
optical fiber
•
Thin as
a human
hair
What
are the advantages and disadvantages of
fiber-optic cable?
Wireless Transmission Media
What is wireless transmission media?
°
Send
communications signals through the air or space
°
Used when it is
inconvenient, impractical, or impossible to install cables
What is broadcast radio?
°
A wireless
transmission medium that distributes radio signals through the air over long
distances such as between cities, regions, and countries and short distances
such as within an office or home
°
Slower and more
susceptible to noise than physical transmission media
What is Bluetooth™?
°
Uses short-range
radio waves to transmit data among Bluetooth™-enabled devices
°
Device contains
a small chip that
allows it to
communicate
with other
Bluetooth™-
enabled devices
What is an example of a wireless
local area network?
What is cellular radio?
°
A form of
broadcast radio that is used widely for mobile communications, specifically
wireless modems and cellular telephones
°
A cellular
telephone
is a telephone
device that uses
radio signals to
transmit voice and
digital data
messages
What
is Personal Communications Services (PCS)?
°
A set of
technologies used for completely digital cellular devices
°
Include handheld
computers, cellular telephones, pagers, and fax machines
°
Devices have
wireless modems allowing you Internet access and e-mail capabilities
What are microwaves?
°
Radio waves that
provide a high-speed signal transmission
°
Involves sending
signals from one microwave station to another
What is a microwave station?
°
An earth-based
reflective dish that contains the antenna, transceivers, and other equipment
necessary for microwave communications
°
Uses
line-of-sight transmission
•
Must transmit in
a straight line with no obstructions between microwave antennas
What is a communications satellite?
°
A space station
that receives microwave signals from an earth-based station, amplifies the
signals, and broadcasts the signals back over a wide area to any number of
earth-based stations
°
Transmission to a
satellite is an uplink
°
Transmission from
a
satellite to an
earth-based station
is a downlink
What is infrared (IR)?
°
A wireless
transmission media that sends signals using infrared light waves
°
Requires a
line-of-sight transmission
°
Many computers
and devices have an IrDA port that enables the transfer of data using infrared
light rays
Summary of Communications and Networks
°
Communications
°
Sending and
receiving devices
°
Uses of
communications technologies
°
Networks
°
Communications
software
°
The telephone
network
°
Communications
devices
°
Communications
channel
°
Physical
transmission media
°
Wireless
transmission media
Chapter
9 Complete