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Chapter 3

Connecting to the World

Copyright 2004 by Zongqing Zhou, PhD

Niagara University

3.1 Establishing a

Standard Connection


To connect to the Internet via
telephone line you will need four basic
things:


A computer


A modem


An internet Service Provider


A browser

Figure 3.1

Analog data

Modulator

Analog
transmission
(public telephone
network)

Analog
transmission
(public telephone
network)

Digital data

Digital data

Digital
transmitter

Modem

Digital
transmission
(Digital data lines
or local area
network)

Modem


Modem comes from


Modulator


Demodulator


A modem is an electronic device for
converting between digital data from a
computer or an audio signal suitable for
transmission over telephone lines.


The speed of data transmission is measured
in bits per second, kilobits per second or in
bauds.


Modem (cont.)


A modems most common speeds are


28,800


36,000


56,000


Modems


Internal


External

ISP and OSP


The gateways


ISP (Internet Service Provider)


OSP (Online Service Provider)

ISP and OSP


ISP


Once connected you are directly connected to the
Internet; it has no control over what you can access on
the Internet.


Most important factors when choosing an ISP:


Local phone number


Other features


Speed


Features


Pricing


Reliability


ISP and OSP


OSP


You are connected to the Internet through
OSP’s server


OSP tends to offer its own programs
which are screened and filtered through
your service provider
.


Figure 3.2


Computer



Modem


ISP


Internet

3.2 Alternative Connections


Broadband communications channels
-

high
-
speed internet access.


ISDN (Integrated Services Digital
Network)


A system of digital phone connections
allowing a single wire or optical fiber to
carry voice, digital network services,
and video. Intended to replace POTS
(plain old telephone system)

3.2 Alternative Connections


Cable modem


Most widely subscribed


Typically faster than DSL


Typically an external device


3.2 Alternative Connections


DSL (Digital Subscriber Line) *leading
method


Plugs into the existing LAN


Best available method of connection


Wireless


No physical connection


Mobility and adaptability



3.2 Alternative Connections


Bandwidth
-

the amount of data that can be
sent through a given communications circuit
per second.

Wireless Terms


WAP (Wireless Applications Protocol)
-

allowing device manufactures and service
providers to be bale to talk to each other, so
that digital content can be delivered to
consumers through the air regardless of
standard used.


WML (Wireless Markup Language)
-

language used to specify content and user
interface.


Wireless Terms


W
-
CDMA or I
-
Mode
-

allows one to view
256 color graphics and HTML on their
phones.


HDML (Handheld Device Markup
Language
)
-

uses its own gateway to provide
access to the wireless Web.


XML (External Markup Language)
-

markup symbols to describe the content of a
page or file.

3.3 Networking: LAN and WAN


LAN
-

local area network


A high speed data communication network
that connects computers and other terminals
within a geographically limited area, typically
within adjacent buildings or complexes.


It is different from PANs (personal area
networks) MANs (metropolitan area
networks), or WANs (wide area networks).


LANs are typically faster than WANs

3.3 Networking: LAN and WAN


Benefits of using networks


Allows sharing of resources like
printers


Easy and fast information sharing


Share software


Response to service request is faster
and better


3.3 Networking: LAN and WAN


Early LANs were vendor specific
and used different standards.


Today there are two common
wiring technologies for a LAN,
Ethernet and Token Ring.


3.3 Networking: LAN and WAN


Wireless technologies are starting to
evolve and are convenient for Mobile
computer users.


When using Ethernet the computers
are usually wired to a hub or to a
switch. This constitutes the physical
transport mechanism.

3.3 Networking: LAN and WAN


LANs can be interlinked by
connections to form a Wide area
network. A router is used to
make the connection between
LANs.


3.3 Networking: LAN and WAN


WAN
-

wide area network


Typically the same as a LAN but
covers more geographical area.


LAN Terms


Firewall
-

is a set of related software programs
that protect the resources of a LAN or a
private network from users from other
networks.


Four main LAN systems:


Ethernet


Token Ring


Arcnet System


FDDI

Figure 3.3

LAN
Internet

Computer

Computer

Computer

Computer

Computer

Firewall

Computer

Internet

Location of a firewall, which guards against unauthorized access to a LAN or Internet.

Figure 3.4

A bus
-
typology Ethernet LAN

Computer

Computer

Computer

Computer

Server

Bus

Figure 3.5

Ring

Computer

Computer

Computer

Computer

Computer

Server

A token ring LAN

Figure 3.6

A wireless LAN with two access points.

Antenna

Workstation

File server

Access point 1

Access point 2

Workstation

Wired Ethernet LAN