Introduction to Web Technology

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5 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Introduction to Web Technology


Internet and Web Application Development

SWE
444

Dr. Ahmed
Youssef

2

Internet

It

is

a

network

of

networks

connected

and

communicating

using

TCP/IP

communication

protocol



Computer Networks


Ahmed
Youssef
:: SWE444: Internet and Web Application Development

3

Brief History of the Internet


1968

-

DARPA

(Defense

Advanced

Research

Projects

Agency)

contracts

with

BBN

(Bolt,

Beranek

&

Newman)

to

create

ARPAnet


1970

-

First

five

nodes
:



UCLA


Stanford


UC

Santa

Barbara


U

of

Utah,

and



BBN


1974

-

TCP

specification

by

Vint

Cerf


1984



On

January

1
,

the

Internet

with

its

1000

hosts

converts

to

using

TCP/IP

for

its

messaging

A Brief Summary of the

Evolution of the Internet

???

Assignment

Intranet & Extranets


Intranet


A

private

network

contained

within

an

organization

or

business

used

to

share

information

and

resources

among

coworkers
.


Extranet


A

private

network

that

securely

shares

part

of

an

organization’s

information

or

operations

with

external

partners

Intranet & Extranets

7

Ahmed Youssef:: SWE444:
Internet and Web Application Development

8

Intranet & Extranets

Components of Web


Web Page and Web Site


Web Browsers and Web Servers


Uniform Resource Locator(URL)


HTML


HTTP


Internet Protocol

9

Web Page vs Website


A

web

page

is

a

part

of

a

complete

web

site
.

It

is

a

document

or

information

resource

that

is

suitable

for

the

World

Wide

Web

and

it

can

be

accessed

through

a

web

browser
.



Websites

can

consist

of

few

web

pages

or

many

hundreds

of

web

pages
.


Ahmed
Youssef
:: SWE444:
Internet and Web Application Development

10

Web Browser


It's a software


It

lets

you

visit

webpages

and

use

web

applications

Types:


Internet Explorer


Mozilla Firefox


Netscape Navigator


Google Chrome


Opera




Web

servers


The

term

web

server

can

refer

to

either

the

hardware

(computer)

or

the

software

(computer

application)

that

helps

to

deliver

web

content

that

can

be

accessed

through

the

Internet
.


The

web

server

hosts

pages,

programs,

and

multimedia

files

and

serves

them

using

HTTP,

a

protocol

designed

to

send

files

to

web

browsers

and

other

protocols
.

12

Accessing a web site

Client computer
Server computer
Internet
connection
Web browser
Web server
Database server
HTML

HyperText

Markup Language


HTML is a coding language used to create
hypertext/hypermedia documents known as
web pages.


Hypertext documents
are documents that can
contain links to other hypertext documents.


Ahmed
Youssef
:: SWE
444
:
Internet and Web Application Development

14

15

HTTP


Hypertext Transfer Protocol


Provides

a

standard

for

Web

browsers

and

servers

to

communicate
.



Set

of

rules

for

transferring

files

(text,

graphic

images,

sound,

video,

and

other

multimedia

files)

on

the

World

Wide

Web
.

Ahmed
Youssef
:: SWE
444
:
Internet and Web Application Development

16

Hypertext Transport Protocol
(HTTP)


Protocol

for

HTML

retrieval

of

and

other

documents

from

website

throughout

the

Internet
.


HTTP

is

based

on

the

request
-
response

communication

model
:


Client

sends

a

request


Server

sends

a

response

Client Server

Server

Client

Client

Client

Request

Response

Client/Server Computing

File Server

Client PC

Client/Server Processing with Request
-
Response Cycle

Client Program

Server Program

Request Message

Response Message

Web
-
Enabled Application

E
-
Mail Server

Client PC

Client is Browser

Server Program

HTTP Request Message

HTTP Response Message

Web
-
enabled applications:

Form of client server processing

that uses browsers as clients
.

20

Internet Protocols

What

is

a

protocol?




A

set

of

rules

governing

the

exchange

of

data

between

two

or

more

hosts
.



The

Internet

Protocol

(IP)

is

the

method

or

protocol

by

which

data

is

sent

from

one

computer

to

another

on

the

Internet
.


Internet Protocol address

(
IP address
)


It

is

a

usually

numerical

label

assigned

to

each

device

participating

in

a

computer

network

that

uses

the

Internet

Protocol

for

communication
.


IP address
:


32
-
bit number (in
IPv
4
)


Written as four dot
-
separated bytes,



e.g.
212.138.86.31
(www.uoh.edu.sa)

22

Transmission Control Protocol
(TCP)


TCP enables two

hosts

to establish a connection
and exchange streams of data.


Provides guarantee that packets delivered


Provide two
-
way (full duplex) communication

23

TCP

Source

Destination

Can I talk to you?

OK. Can I talk to you?

OK.

Here’s a packet.

Got it.

Here’s a packet.

Here’s a resent packet.

Got it.

Establish

connection.

{

{

{

Send packet

with

acknowledgment.

Resend packet if

no (or delayed)

acknowledgment.

24

URL is a standard way to specify the location of a resource

URLs are the unique addresses of Internet Resources.

A URL is divided into four parts.


Transfer protocols


Server name


Directory path


File name


Uniform Resource Locator

General URL syntax


<scheme>:<scheme
-
dependent
-
information>


Scheme examples:


http


(Hyper Text Transfer Protocol)


ftp


(File Transfer Protocol)


news


(News protocol
)


scheme://Server name/path/filename



Example

http://www.uoh.edu.sa/a.khedr/swe
444
.html


Transfer Protocol:

Server name:



Directory Path:

File name:

Ahmed Youssef:: SWE
444
:
Internet and Web Application Development

26

Domain Name Service (
DNS
)


DNS is the “phone book” for the Internet


Map between host names and IP addresses


Host names


Labels separated by dots, e.g.,
www.example.org


Final label is
top
-
level domain


Generic: .com, .org, etc.


Country
-
code: .us, .
sa
, .
eg
, etc.

http://en.wikipedia.org/wiki/List_of_Internet_top
-
level_domains

27

Types of Web Sites


Static
:


It

contains

a

fixed

amount

of

pages

and

the

information

is

presented

in

HTML
.



Dynamic
:


the

content

changes

every

time

the

page

loads
.

This

change

in

content

will

directly

be

related

to

the

latest

updated

information

present

on

the

database

.

Ahmed Youssef:: SWE
444
:
Internet and Web Application Development

28

Accessing static web pages


“Static”



the

contents

don’t

change

(unless

they’re

edited)
.


Web

pages

(text

files)

and

other

needed

files

(e
.
g
.

images)

are

stored

as

files

on

the

web

server

and

are

retrieved

as

needed

in

response

to

HTTP

requests

Client
Server
Browser
Web server
HTML file
HTTP request
HTTP response
Types of web sites based on content


Information


Search Engines


Educational


Forums


Company


Online shops





Ahmed Youssef:: SWE
444
:
Internet and Web Application Development

30

The World Wide Web (WWW)


The

World

Wide

Web

consists

of

all

the

public

Web

sites

connected

to

the

Internet

worldwide


The Web consists of three distinct technologies


H
yper
T
ext
M
ark
-
up
L
anguage

(
HTML
)


H
yper
T
ext
T
ransport
P
rotocol

(
HTTP
)


U
niform
R
esource
L
ocators

(
URLs
)

Difference Between Internet and Web?


World Wide Web

is the
Multimedia

portion of
the
Internet


Images, video, sound, animation, etc.


Technically the Web is the portion of the
Internet that contains Web Servers, and Web
Sites.


33

Client Caching


A cache is a local copy of information gets
from some other source

34

Client Caching

Browser

Web

Server

1
. HTTP request for image

2
. HTTP response containing image

Client

Server

Cache

3
. Store image

35

Client Caching

Browser

Web

Server

Client

Server

Cache

I need that

image

again…


HTTP request for image

HTTP response containing image

This…

36

Client Caching

Browser

Web

Server

Client

Server

Cache

I need that

image

again…

Get

image

… or this

37

Client Caching


Cache advantages


(Much) faster than HTTP request/response


Less network traffic


Less load on server


Cache disadvantage


Cached copy of resource may be invalid
(inconsistent with remote version)

38

Secure Servers


Since HTTP messages typically travel over a
public network, private information (such as
credit card numbers) should be encrypted to
prevent eavesdropping


https URL scheme tells browser to use
encryption


Common encryption standards:


Secure Socket Layer (SSL)


Transport Layer Security (
TLS
)

39

Secure Servers

Browser

Web

Server

I’d like to talk securely to you (over port
443
)

Here’s my certificate and encryption data

Here’s an encrypted HTTP request

Here’s an encrypted HTTP response

Here’s an encrypted HTTP request

Here’s an encrypted HTTP response

TLS/

SSL

TLS/

SSL

HTTP

Requests

HTTP

Responses

HTTP

Requests

HTTP

Responses