Chapter 2 Intro to computer network - UAH Personal Web Pages

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Chapter 2

Introduction to
Computer Network

What is a Computer
Network

(Network)?


Two or more computers



connected



Sharing/exchanging resources

(e.g., file,
printer,
Webpages
)



What is a Computer?



Data manipulation device



Hardware

components



Software

components


Hardware Components


Data Processing

components:


Central processing unit (CPU)

,
Main memory (RAM, ROM)




Data Storage

components :


Secondary memory/storage (hard disk, floppy disk, CD, DVD, tape)




Input

components :


Keyboard, Mouse



Output

components :


Monitor, Printer



Networking

components :


Network interface card (NIC)

,
Hub/switch/router, UTP CAT
5
e cable


Is it a computer network?

Software Components


Operating systems
(OS) software (e.g., Microsoft
Windows XP, Microsoft Windows Vista)




Document editor
(e.g., Microsoft Word, WordPerfect)



Spreadsheet
(e.g., Microsoft Excel)



Database

(e.g., Microsoft Access)



Networking software/programs
(e.g., TCP/IP, IPX/SPX,
NetBEUI, Apache, Internet Explorer, Mozilla Firefox)


Goal of Networking


To make sure a resource shared by a remote
system (
remote resource
) function like a
resource on a local system (
local resource
)



The user should
not

be able to distinguish
between remote resource and local resource
while he/she is using them


Local Computer, Local Resources, Remote Computer,
Remote Resources, Shared Resources


Local computer:


Being used by a user physically



Local resources:


Available in a local computer



Remote computer:


Not being used by a user physically,


Being accessed by a user over a network from the local computer



Remote resources:


Available in a remote computer

User

Local

Local

Local

Local Computer, Local Resources,

Remote Computer, Remote Resources, Shared Resources

Remote

Remote

Remote

Remote

Remote

Remote



Shared resources


Resources


Available in a computer


Accessible by another computer over a network



Controlled by
server


Accessible from
client

Local Computer, Local Resources, Remote Computer,
Remote Resources, Shared Resources

Sharing Resources:

The Concept of Client and Server



Server
:


Providing networking services



Client
:


Requesting and receiving the networking services

The Concept of Client and Server



What are examples of networking
services?



Sharing file


File

server (read the “No file sharing”
tech note on page 16)


Sharing printer


Printer

server


Sharing Webpage


Web server


Email transfer service


Email server


Online chatting service

The Concept of Client and Server

Print client
3

Print client 2

Print client 1

The Concept of Client and Server

Web client

The Concept of Client and Server

How to create a Server?


To set a computer to be a
server
,



Step
1
.
Connecting the computer to a
network



Step
2
.
Installing and running

a
server

program

in the computer


What is a server program?

How to create a Client?


To set a computer to be a
client
,



Step 1.
Connecting the computer to a
network



Step 2.

Installing and running

a
client
program


What is client program?

The Concept of Client and Server

Print client software

Print client software

Print client software

Print server software

The Concept of Client and Server

Web client

Web client
software

Web server
software

The Concept of Client and Server

Email client
software

Email client
software

Email server
software

Email server
software

How many clients? How many servers?


How many client programs can be run by a
computer?



How many server programs can be run by a
computer?



Can a computer run client and server
programs at the same time?

Client/Server Network Versus

Peer
-
to
-
Peer (P2P) Network



Client/Server Network:


There is (at least one) server
-
only computer



Peer
-
to
-
Peer Network:


ALL

computers are
BOTH

clients and servers (run
BOTH client and server)



What is Peer
-
to
-
Peer program?


http://en.wikipedia.org/wiki/Peer
-
to
-
peer

Client/Server Network Versus

Peer
-
to
-
Peer (P
2
P) Network

Client &
Server

Client &
Server

Client &
Server

Client

Client

Client

Server

How to share a resource?


Running the
server software



Using the server software
to specify the
shared resource


Defining a
network name
to the shared resource
(i.e., a name to “call” the resource from a client)


Defining a
permission

(i.e., a defined set of what
the user can/cannot do with the resource)

How to access a shared resource?


Running the
client software



Using the client software
to “call” the
resource

by using its network name



How do you know the network name?


Somebody tells you


By using a “search” engine


By using a “browser”

What Type of Computer can be set to
be a Server?


Micro
-
computer


Desktop computer


Laptop computer



Mini
-
computer


Mainframe computer



(server)



Super
-
computer



Higher storage capacity




Higher information processing speed




Larger size (physically)

Micro
-
computer (e.g., desktop computer) versus

Mini
-
computer (mainframe computer)


versus Super
-
computer

Micro
-
computer

Mini
-
computer

versus

Super
-
computer

versus

What Type of Computer is usually used as a
server in mid
-

to large
-
organizations?


Mini
-
computer/Mainframe/Server


Classes of Network based on
Size/Coverage


Personal Area Network

(PAN)



Within the reach of a single person (within a few feet around
a single person)



Local Area Network

(LAN)



Within a building
or
a single geographic area that belongs to
a single organization



Classes of Network based on
Size/Coverage


Metropolitan Area Network

(MAN)



In different locations within a single city/metropolitan area



Wide Area Network

(WAN)



In different cities/metropolitan areas, different states,
different countries



Classes of Network based on Accessibility


Private network


A network that is accessible by people belonging to a certain
organization only


Example: UAH network



Public network


A network that is accessible by public


Example: the Internet



Classes of Network based on
Size/Coverage


What is Virtual Private Network (VPN)? Which class (PAN,
LAN, MAN, WAN) does it belong to?



A VPN is a private network that
uses a public network
(usually the Internet) to connect remote sites or users
together privately (NOT everybody can join the network,
only people belonging to a certain organization only
)