Internet Services and

cottonseedfearnotElectronics - Devices

Nov 7, 2013 (3 years and 5 months ago)

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Chapter 3

Internet Services and
Operating System

Network and Comutication

Communications

What is computer communications?


A process in which one computer transfers data, instructions,
and information to another computer(s)

A communications
system contains all
types of devices

(a)

personal
computers

(b)

notebook
computers

(c)

Web
-
enabled
cellular telephones

(d)

Web
-
enabled
handheld computers

(e)

WebTV


(f)

GPS receivers

a

a

d

c

b

e

a

a

f

c

Communications

sending device

Initiates an instruction to transmit
data, instructions, or information

communications device

Converts or formats the data, instructions, or
information from the sending device into
signals carried by a communications channel

communications channel

A path on which the signals travel

communications device

Receives the signals from the communications
channel and converts or formats them so the
receiving device can understand the signals

receiving device

Accepts the data, instructions, or information

What is needed for successful communications?

Communications

What is the primary function of a communications
device?

analog signal

A continuous
electrical wave

digital signal

Individual electrical
pulses that represent
the bits grouped
together into bytes


To convert or format signals so they are suitable for the
communications channel or a receiving device

mainframe computers

mid
-
range servers

desktop computers

notebook computers

Sending and Receiving Devices

What is a sending and receiving device?


Initiates or accepts transmission of data, instructions, and
information

Internet appliances and
Web
-
enabled devices

Sending and Receiving Devices

What are some specialized sending and receiving
devices?

p.9.3 Fig. 9
-
3

Next

Internet appliance

Also called a Web appliance

Computer with limited
functionality whose main
purpose is to connect to the
Internet from home

Web
-
enabled device

Handheld device that provides
access to the Internet and e
-
mail from any location

Internet
appliance

Web
-
enabled
cellular
telephone

Web
-
enabled
handheld computer

set
-
top
box

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

p.9.11

Next

share data and
information

facilitate
communications

share
hardware

share software

Networks

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

p.9.12 Fig. 9
-
9

Next

Networks

What is a node ?


Each computer or device on a network

p.9.12

Next

Often the nodes are
connected to the
LAN via cables

A wireless LAN
(WLAN) is a LAN
that uses no
physical wires

node

node

node

node

node

Networks

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

p.9.13 Fig. 9
-
11

Next

printer may be used by
all computers on
network

network operating
system and
application software
installed on each
computer

Networks

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


p.9.14 Fig. 9
-
12

Next

client

client

client

server

laser printer

Networks

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

p.9.14

Next

database server stores and
provides access to a database


network server

manages network traffic

print server manages
printers and print jobs

file server stores and
manages files


Clients


Other computers on the
network


Rely on the server for
resources


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

p.9.15 Fig. 9
-
13

Next

communications
satellite

Networks

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

p.9.16 Fig. 9
-
14

Next

Networks

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

p.9.14

Next

Networks

What is a network topology?


The configuration, or physical arrangement, of the devices in a
communications network


Networks usually use combinations of three topologies

p.9.16

Next

ring

star

bus

Networks

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

p.9.17 Fig. 9
-
15

Next

personal
computer

personal
computer

personal
computer

personal
computer

personal
computer

Networks

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

p.9.16 Fig. 9
-
16

Next

Networks

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

p.9.17 Fig. 9
-
17

Next

host
computer

printer

file server

personal computer

personal computer

personal computer

personal computer

Networks

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

p.9.18

Next

Ethernet

token ring

TCP/IP

WAP

original Ethernet standard

not very fast by today’s
standards, but works well for
small to medium networks


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

p.9.19

Next

Fast Ethernet

transmits data and
information at speeds up to 10
times faster than the original
standard

Gigabit Ethernet

provides an even higher speed of
transmission, with speeds up to
10 times faster than Fast Ethernet

Networks

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

p.9.19

Next

Networks

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

p.9.19

Next

packets

Data is divided into small
pieces called packets

routers

Devices that direct
packets along the fastest
available path

packet switching

Technique of breaking a
message into packets, sending
the packets, and then
reassembling the data

Networks

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

p.9.20

Next

Networks

p.9.20

Next

uses TCP/IP
technologies

has a Web server

supports multimedia
Web pages coded in
HTML

accessible via a
Web browser

users can post and update
information on the intranet
by creating and posting a
Web page


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 intranet?

Networks

What is an extranet?


Allows customers or
suppliers to access
part of a company’s
intranet

p.9.20 Fig. 9
-
18

Next

Networks

What is a firewall?


A general term that refers to hardware and/or software that
restricts access to data and information on a network

p.9.20 Fig. 9
-
19

Next

personal computer

personal computer

personal computer

personal computer

personal computer

personal computer

personal computer

printer

firewall

corporate
network

Internet

The Telephone Network

What is the public switched telephone network (PSTN)?


The worldwide telephone system that handles voice
-
oriented
telephone calls

p.9.25 Fig. 9
-
24

Next

satellite

most of the PSTN uses
digital technology

analog signal

analog signal

final link from local telephone
company to home or office

The Telephone Network

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

p.9.26 Fig. 9
-
26

Next

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

p.9.27

Next

dial
-
up modems

ISDN and DSL
modems

cable
modems

network
interface cards

Communications Devices

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


p.9.28

Next

mo
dulate

To change into
an analog signal

dem
odulate

To convert an
analog signal into a
digital signal

mo + dem

Communications Devices

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

p.9.28 Fig. 9
-
27

Next

DSL modem

Sends and receives
digital data and
information to a DSL line

Communications Devices

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


p.9.28

Next

ISDN modem

Also called an ISDN adapter

Sends and receives digital data
and information from your
computer to an ISDN line

Communications Devices

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

p.9.29 Fig. 9
-
28

Next

Communications Devices

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

p.9.29 Fig. 9
-
29

Next

NIC for desktop
computer

NIC for notebook
computer

Communications Devices

What is a hub?


A device that
provides a
central point
for cables in a
network

p.9.30 Fig. 9
-
30

Next

Bandwidth

Width of the
communications channel

The higher the bandwidth,
the more data and
information the channel can
transmit

Communications Channel

What is a channel?


The communications path between two devices

p.9.31

Next

Transmission media

Materials or techniques
capable of carrying one or
more signals

When you send data from your
computer to another device,
the signal carrying the data
most likely travels over a
variety of transmission media

Step 1: Sending device
requests information
using either a physical
transmission media or a
wireless transmission
media.

sending device

modem

ISP

microwave station

Step 2: When the
request leaves the ISP,
it travels over T1 lines,
microwave stations,
earth
-
based stations,
and communications
satellites until it
reaches the Internet
backbone.

mainframe computer

T1 lines

earth
-
based stations

communications satellite

T1 lines

Communications Channel

What is a typical communications channel?

p.9.31 Fig. 9
-
31

Next

Step 3: The request
travels over T3 lines
along the Internet
backbone.

T3 lines

mainframe computer

T3 lines

Internet
backbone

Step 4: The request
travels over T1 lines
until it reaches the
destination network
server.

T1 lines

destination
network server

Communications Channel

What are characteristics of transmission media?

p.9.32

Next

baseband versus broadband


Baseband media can
transmit only one signal at
a time


Broadband media can
transmit multiple signals
simultaneously

physical versus wireless


Physical transmission
media use wire, cable,
and other tangible
materials


Wireless transmission
media send
communications
signals though the air
or space

Physical Transmission Media

What is physical transmission media?


Wire, cable, and other tangible (touchable) materials used to
send communications signals

p.9.32 Fig. 9
-
32

Next

twisted pair cable

twisted pair cable

twisted pair wire

Physical Transmission Media

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

p.9.33 Fig. 9
-
33

Next

coaxial cable

plastic outer
coating

woven or
braided metal

insulating
material

copper wire

Physical Transmission Media

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

p.9.33 Fig. 9
-
34

Next

fiber
-
optic cable between
floors of a building

cable
contains
many optical
fibers

outer
covering
jacket

Physical Transmission Media

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

p.9.34 Fig. 9
-
35

Next

protective
coating

glass
cladding

optical
fiber core

Physical Transmission Media

What are the advantages and disadvantages of fiber
-
optic cable?

p.9.34

Next

Disadvantages


Costs more than wire


Can be difficult to install
and modify

Advantages


Able to carry significantly
more signals than wire


Faster data transmission


Less susceptible to noise
from other devices


Better security for signals
during transmission


Smaller size

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

p.9.34 Fig. 9
-
36

Next

transmitter

sends the
broadcast radio
signal

Wireless Transmission Media

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


p.9.35

Next

receiver

accepts the broadcast
radio signal

must have an antenna that
is located in the range of
the signal

transceiver

both sends and receives
signals from wireless
devices

Step 1: A customer
buys a movie ticket
over the Web and
downloads it to a
handheld computer.

Step 1

Step 2

Step 2: The
handheld computer
stores a “proof
-
of
-
purchase voucher.”

Step 3

Step 3: A Bluetooth™
-
enabled reader scans
the voucher.

Wireless 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

p.9.35 Fig. 9
-
37

Next

Step 4: The
customer is
admitted to the
movie theatre.

Step 4

Wireless Transmission Media

What is an
example of
a wireless
local area
network?

p.9.36 Fig. 9
-
38

Next

switch

access
point

Wireless Transmission Media

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

p.9.36 Fig. 9
-
39

Next

mobile telephone
switching office
(MTSO)

cell

cell

cell

cell

calling party
in auto

called
party

public switched
telephone
network

base station
(microwave
station)

Wireless Transmission Media

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

p.9.37

Next

Wireless Transmission Media

What are microwaves?


Radio waves that
provide a high
-
speed
signal transmission


Involves sending signals
from one microwave
station to another

p.9.38 Fig. 9
-
40

Next

Wireless Transmission Media

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

p.9.38 Fig. 9
-
40

Next

Wireless Transmission Media

What is a communications satellite?

p.9.38 Fig. 9
-
41

Next


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

Wireless Transmission Media

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

p.9.39 Fig. 9
-
42

Next

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