3.2 The internet

morningbreadloafΔίκτυα και Επικοινωνίες

30 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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3.2
The internet


A worldwide system of computer networks


A network which users can (with permission) get
information from any other computer


The original aim of creating internet was to
create a network that would allow users of a
research computer at one university to be
able to "talk to" research computers at other
universities


Today the Internet is a public, cooperative,
and self
-
sustaining facility accessible to
hundreds of millions of people worldwide

3.2.1
Historical Background of
the Development of the Internet

1.
The birth of the Internet


Was created for military purposes by
ARPANET (Advanced Research Projects
Agency Network) in 1969


Transmission speed was slow (56kbps)


System was made up of research institutes
and universities inside the US connected
by a packet network


3.2.1
Historical Background of
the Development of the Internet

2.
Development of the basic technology


TCP/IP is the fundamental technologies and the
standard protocol on the Internet

3.
Development of networks(1980)


1983


no more military network,remain science
and research


1986


started as independent network


3.2.1
Historical Background of
the Development of the Internet

4.
The rapid grow of the Internet(1990s)


The birth of commercial networks


NII (National Information
Infrastructure) plan


Increasingly powerful computers


3.2.2
The Structure of the Internet

1.
A network of networks


Many small LANs and WANs joined together
to become a big network

2.
Different between the Internet and Personal
computer communication


Personal computer communication

networks are
runs by companies that have a host computer
and offer various services such as database


Internet has no mother organization, anyone can
receive services

3.2.2
The Structure of the Internet

3.
The Internet and TCP/IP


Have to employ this communication protocol to
access to internet


Not managed by any international organization


De facto standard protocol


Internet

ISP (Internet Service Provider)

Skyinet

Infocom

AAA


Pacific

CCC

Access Point

Access Point

ISDN

Internet

Leased Line Connection

ISP

Network in office

Network in office


High speed digital line



Kbps

6Mbps


Internet

ISP

Network in office

Home, Hotel etc

Network type

Dial
-
up Connection

Terminal type

Dial
-
up Connection

ISDN

Land Line




Land Line
(~
56Kbps


††

I卄N

††††


Kbps

128Kbps


Dial
-
up Connection

3.2.3
Internet Technology

1.
IP routing


Each computer connected to the network is
given an IP address(unique address)


IP routing is a technique that determines the
transmission route from the sender to the
destination

3.2.3
Internet Technology

2.
DNS (Domain Name System)


Readable name instead of IP (all numbers)


One
-
to
-
one coordination between a domain
name and the IP address


Tell you

which country



what kind of
organization



who


from the address

Root Domain

net

com

jp

uk

xxx

fujitsu

yyy

jp

pr

aaa

aaa.fujitsu.com

domain

Expression of Host name




svr1
.
aaa.fujitsu.com.


Host name
.
Domain name

svr1

FQDN

Domain

Domain aaa

Domain bbb

Mail Server

Mail Server

1

2

3

4

5

6


1.
Creation of an e
-
mail


2.
Sending the e
-
mail


3.
Analysis of the destination


4.
Sending the e
-
mail to Domain bbb by mail server


5.
Acceptance of the e
-
mail and keep in the mail server


6.
Get the e
-
mail

Internet

E
-
mail

5.5.1

電子メールアドレス

e
-
mail address


User Identification


Consist of user name and domain name

User name

Domain name

Separation

Notation



u獥s n慭敀eom慩a 乡Ne

攮e.



h楲o
@
fu橩j獵⹣.m⹰h

WWW

Client

Browser

HTML data

Media data

WWW

Server

HTML

data

Media data

WWW

Server

Requirement


啒U


Da瑡 send

Da瑡 send

Requirement


啒U


WWW

5.6.1

URL

Notation



Protocol://Server name
/
Directory path/File name

URL;


Syntax for access to the information on the Internet

e.g.



http://www.fujitsu.com.ph/about/index.html

Mechanism for Delivery of HTML Documents

http://www.flm.co.jp/flm/flm.html

directory

flm

http://www.flm.co.jp/flm/

www.flm.co.jp

WWW

client

WWW

server

http://www.flm.co.jp/

Document
root


htdocs

HTML file

(default document)

index.html

Image file

image.gif

HTML file

(default document)

index.html

HTML file

flm.html

WWW

server

WWW

client


CGI scripts

Processing

programs

database

browser

Request for HTML file/image file by URL


Call CGI scripts by URL

Send HTML file/image file

Send processed

HTML document

WWW service


HTML

contents

WWW Server Features

Host name : mars

IP address: 202.248.79.66

flm.co.jp domain

When DNS is not used

When DNS is used

mars

IN

A

202.248.79.66

www

IN

A

202.248.79.68

To 202.248.79.66

To mars.flm.co.jp

connection

connection

What is DNS











FTP

Client

Control process

User

Interface











Port #21

Port #20

Command

Reply

Data transfer

FTP

Server

File

File

I/O

I/O

User

Require

Result

Transfer process

FTP

3.2.6
Search Engine


An information retrieval tool


Search Engine

1.
Directory type

: www.yahoo.com

2.
Robot type



program that automatically
search WWW : www.google.com


Search Methods

1.
Keyword search



Based on keyword

2.
Directory search



Narrow search object to
fields

3.2.7
Internet Related Knowledge

1.
Quality of Service



indicate the quality of service

2.
xDSL (x Digital Subscriber Line)



High speed
transmission

3.
Best Effort Service



Low charges and no guarantee
of service

4.
CGI (Common Gateway Interface)



Interface
between WWW server and programs

5.
VoIP (Voice over IP)



Voice data transmission
technology employing the IP protocol

xDSL

ISP

Home

Digital data

Telephone

Unused frequency

Telephone cable

DSL

Digi瑡l 卵bscriber Line

瑥chnology is used.

Broad band service 瑯 use 瑥lephone line ⡭e瑡llic cable)


DSL

service

Uses DSL(Digital Subscriber Line) Technology.

Analog line

100
M

30M


20M


10M


5M

2M

1M

500k

200k

100k


300


1
Km 2Km 3Km 4Km 5Km 6Km

ADSL

HDSL

VDSL

Symmetric

Asymmetric

xDSL service

ADSL
;

Different frequency is used on up
-
stream and down
-
stream

Internet

phone

Splitter

Splitter

ADSL MODEM

Home

ISP

Telephone cable

VoIP service

PBX

PBX

VoIP

Router


LAN

Voice

WAN


VoIP

Router



DNS



WWW



Mail

Internet

Public server

Barrier segment

Local segment

router

Firewall

Access

denied

Access

allowed

Access

allowed

What is a Firewall

Upper

level

Lower

level

Application level

TCP/IP level

<
Firewall>

Internet

Internal network

Firewall Technologies

(Packet Filtering)

Internet

Public server

Internal server

Barrier segment

x

Local segment

Proxy

router

Overview of Proxy Server

Proxy server

x

Accept

requests

blocked

Internal client


( browser)

Firewall

(1)

(2)

(4)

(3)

(5)


External server


( WWW server)

Proxy Server Features


External server

( Internet )

IP address
:
172.20.1.4

Proxy server

IP address
:
172.20.1.3

http protocol

ftp protocol

x

x

Filtering by
protocol

Access
control via
IP address

Internet

Internal
network

Access Control and Filtering

Proxy server

Internal client

Fujitsu WWW server


(external server)

Internal client

Request for
Fujitsu
homepage


data
caching

(6)
Request for
Fujitsu homepage

(7)
Retrieving
cache data

(1)

(2)

(4)

(3)

(5)

Fujitsu homepage

F L M homepage










Cache Feature