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Unit-1 Introduction WWW. Prepared by: Prof. Harish I Rathod Computer engineering department Gujarat power engineering & Research institute. WEB APPLICATION DEVELOPMENT (170705). History of WWW. The WWW (W3) is the part of history of the internet .

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unit 1 introduction www

Unit-1 Introduction WWW

Prepared by:

Prof. Harish I Rathod

Computer engineering department

Gujarat power engineering & Research institute

WEB APPLICATION DEVELOPMENT (170705)

history of www
History of WWW
  • The WWW(W3) is the part of history of the internet.
  • Invented by Tim-Berner-Lee in 1980,
  • For the purpose of, how computers could store information with random link.
  • In 1989 he proposed the idea of a global hypertext space,
  • In which any network-accessible information could be referred to by a single “Universal Document Identifier (UDI)”.

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history of www1
History of WWW
  • This idea was expanded in 1990 with a program called “World Wide Web (WWW)”.
  • Then after development led to:
  • Browser,
  • Web server,
  • Hyper Text Markup Language (HTML),
  • Hyper Text Transfer Protocol (HTTP).

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the internet and the www
The INTERNET and The WWW
  • The internet works by defining an address for each resource attached to it.
  • This address is known asInternet Protocol (IP) address.
  • Without IP address,no link could be formed between computers, resource or system.
  • Example of an IP address is : 153.162.131.236.
  • The number break down to a country, to a specific domain, to a machine itself.

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the internet and the www1
The INTERNET and The WWW
  • Generally we don’t use numbers to find resources and machine.
  • We use name like xyz.co.in.
  • Each name have an associated number.
  • When name entered into a Web Browser,
  • The computer will use a special system called Domain Name System (DNS) to lookup the associated number, to get in contact with desired server.

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the internet and the www2
The INTERNET and The WWW
  • The Basic Idea behind IP addressing.

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the internet and the www3
The INTERNET and The WWW
  • The basics of the actual communication take place.
  • Any communication occurs on the internet uses the TCP/IP (Transport Control Protocol/Internet Protocol) suite.
  • It is a set of communication protocol for dialogue (interchange or discussion) between computers and devices.
  • This protocol implement a stack,
  • At each layer solve a problems relating to the transmission of data and providing a service to the higher layers.

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the internet and the www4
The INTERNET and The WWW
  • Higher layersare logically closer to the user and relay on lower layers.
  • Operating System Interconnection (OSI) model.
  • OSI model was theoretical and produced at an earlier stage in the evolution of network.
  • The Internet model or TCP/IP model produced as practical solution.

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the internet and the www5
The INTERNET and The WWW
  • OSI Model.

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the internet and the www6
The INTERNET and The WWW
  • Internet Layered (TCP/IP) Model.

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the internet and the www7
The INTERNET and The WWW

Physical layer:

  • Deal with physical characteristics of communication such as,
  • Which kind of medium use for communication (e.g. wires, fiber optic, or radio links).
  • And other related detail such as,
  • Connectors, channels, modulation, signal strengths,
  • level synchronization,
  • Timing and distance.

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the internet and the www8
The INTERNET and The WWW

Data Link layer:

  • Specifies how packets of information are transported over the physical layer.
  • For example:
  • How it is framed or set out with special start and stop bit pattern.

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the internet and the www9
The INTERNET and The WWW

Network layer:

  • Concern with how the packets are transferred over and between network.

Transport layer:

  • Deal with solving problems like reliability,
  • For example:
  • Determine whether the data transferred correct or not.

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the internet and the www10
The INTERNET and The WWW

Application layer:

  • Program use to communicate across a network with other program.
  • Data is passed from the program in an application format and encoded into some standard protocol.

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the internet and the www11
The INTERNET and The WWW

Checkpoint:

  • Initial was need for information exchange between systems.
  • Networks require common convention (agreement or bond) for dialogue or discussion (protocol).
  • Each resource in a network needs a unique identifier (IP address).
  • An IP address can be associated with a name using DNS.
  • A stack of protocols exist, providing services and communication between the various levels in a system.

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protocols and programs
Protocols And Programs
  • Few aspects (features or part) to be considered to enable communication between parties:
  • Where the communication take place (a specific port, a kind of interface for communication over a network)
  • How it take place.
  • The rules and conventions involved.

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protocols and programs1
Protocols And Programs
  • There are many ways of communicating between machines and device.
  • A few contexts in which we may usually wish to transfer information between systems and the mechanisms available for the task.
  • File,
  • Email, Instant Messaging,
  • Remote Machine Access and Web Pages.

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protocols and programs2
Protocols And Programs

File:

  • If we want to send a file from one machine to another, how would we do it?
  • Possible solution:
  • Simply email it and pick up the mail on other machine.
  • Problem: What it there is no client email or the file is simply too large?

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protocols and programs3
Protocols And Programs

File:

  • We can use a disk or memory of some kind,
  • Another way is,
  • We can use File Transfer Protocol (FTP) to load a file either directly on a machine, or to a server.
  • For example we want to transfer a file called myIndex.doc using FTP.

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protocols and programs4
Protocols And Programs

File:

>ftp mysuperserver.co.uk

Connected to mysuperserver.co.uk

220 FTP Server ready

Name : abc

Password:

ftp>put myIndex.doc

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protocols and programs5
Protocols And Programs

File:

  • Commonly used commands are:
  • ftp – start an ftp session
  • ls – list files
  • get – download a file from the server
  • put – upload a file to the server
  • mkdir – make a directory on server

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protocols and programs6
Protocols And Programs

File:

  • cd – change to a new directory on the server
  • close – close the connection
  • open – open a new connection
  • bin – binary mode transfer
  • asc – ASCII text mode transfer

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protocols and programs7
Protocols And Programs

Email:

  • Email exitedas long as 1965.
  • Extended to work on networksbetween many computers.
  • How modern Email works?
  • User, writing their message using a mail client program (or Mail User Agent MUA),
  • Then use Simple Mail Transfer Protocol (SMTP) to send the message to the local Mail Transfer Agent (MTA).

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protocols and programs8
Protocols And Programs

Email:

  • MTA usually exist on the user’s ISP.
  • The MTA deciphers the email address of the recipient (who the email is to!).
  • Form of email address is myname@myaddress
  • Where,
  • myname = local part and
  • myaddress = domain name.

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protocols and programs9
Protocols And Programs

Email:

  • MTA uses the DNS to find the appropriate mail exchange serveraccepting message from that domain.
  • Once the mail server is found, the message is sent on using SMTP,
  • And from there it is placed using the local name(myname) to find the correct mail box.

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protocols and programs10
Protocols And Programs

Email:

  • To pick up the mail,
  • A user’s client retrieves it from the mail box via his MUAusing Post Office Protocol (POP3).

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protocols and programs11
Protocols And Programs

Instant Messaging:

  • It’s possible to use an Instant Messaging (IM) service to talk a friend on another computer.
  • How does this work?
  • It can be possible with Internet Relay Chat (IRC).
  • It is designed for group communication in channels and also allow one to one communication.
  • IRC is an open protocol that uses TCP.

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protocols and programs12
Protocols And Programs

Remote Machine Access:

  • If we need to access a machine from a distance to run a program or retrieve some data, there are a few ways to do this.
  • One way is through Telnet,
  • Which allows us:
  • To open a connection on a remote machine and
  • Issue a command.

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protocols and programs13
Protocols And Programs

Remote Machine Access:

  • The important thing is:
  • The other end of the connection must be process as a server.
  • Telnet uses port 23.
  • Providing less security.
  • Does not providing encrypt to any communication, so password is open for every one.
  • Also possible to hijack.

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protocols and programs14
Protocols And Programs

Remote Machine Access:

  • Due to lack authentication between the parties:
  • it is impossible to know whether parties are involved or not.
  • A better remote access id SSH (Secure Shell),

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protocols and programs15
Protocols And Programs

Remote Machine Access:

  • A SSH session run like:

Raptor – Computer :~ ralphmoseley$ sshralph@192.168.1.4

Password : [type password]

aphid#ls

aphid#logout

Connection to 192.168.1.4 closed

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protocols and programs16
Protocols And Programs

Web Pages:

  • The main protocol use for a communication between browser and a web server is HTTP.
  • It is designed to enable document to be transferred but can be used with other types of data too.
  • For Web document the HTTP protocol works by sending command over a TCP connection.

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protocols and programs17
Protocols And Programs

Web Pages:

  • To understand the how information passed from machine to machine,
  • we need to know how such system can connect to each other.
  • Generally, for the Web, client-server model is use.

Client

(browser)

Server

Hppt://www.mysports.com/index.html

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protocols and programs18
Protocols And Programs

Web Pages:

  • The first stage is the user typing a URL in the browser address window.

192.168.18.32

Port 80

Client

(browser)

Server

Hppt://www.mysports.com/index.html

192.168.18.32

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protocols and programs19
Protocols And Programs

Web Pages:

  • In the next stage the URL is converted to an IP address,
  • IP address is use to make a connection via port 80,
  • The port 80 is use for HTTP and Web.

GET index.html

Client

(browser)

Server

HTTP/1.1

Hppt://www.mysports.com/index.html

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protocols and programs20
Protocols And Programs

Web Pages:

  • Once the connection is established,
  • The client application extracts the file name that is required from the URL and send the request down the established connection.

HTTP/1.1 200 OK

Client

(browser)

Server

[Content of document]

Hppt://www.mysports.com/index.html

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protocols and programs21
Protocols And Programs

Web Pages:

  • The HTTP message is sent saying that the page was found, followed by the page itself.
  • When the page has been sent the connection is dropped.

HTTP/1.1 200 OK

Client

(browser)

Server

[Content of document]

Hppt://www.mysports.com/index.html

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protocols and programs22
Protocols And Programs

Web Pages:

  • The HTTP message is sent saying that the page was found, followed by the page itself.
  • When the page has been sent the connection is dropped.
  • The following HTTP command may originate from a browser to request a Web page from a server:

GET/index.html HTTP/1.0

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protocols and programs23
Protocols And Programs

Web Pages:

  • This Command is text-based command. Has several fields.

Request

Line

Optimal HTTP Header

“\r\n”

Optimal Data

Additional Information such as browser being used, media types accepted

User data (e.g. contents of completed form)

Type of request (e.g. GET)

Delimiter

Carriage return

Line feed

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protocols and programs24
Protocols And Programs

Web Pages:

  • Types of error code:
  • 404 = Not found.
  • 401 = Unauthorized.
  • 500 = Internal server error.
  • 501 = Not implemented.

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secure connections
Secure Connections
  • Most of the protocol are not secure.
  • They use plain text to transfer data, it could be viewed or tempered with at some stage.
  • There are some protocols that make it more secure to send and receive data.
  • Which include:
  • Special version of FTP as SFTP/FTPS and
  • HTTP as HTTPS.

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secure connections1
Secure Connections
  • SSH and various virtual network toolsallows a user to create a secure tunnel through the host machine.
  • SSH allows communication in a secure manner over port 22, with encryption,
  • Which minimizing the risk of tempering.
  • SSH allows the user to log in and execute commands on a remote computer.

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secure connections2
Secure Connections
  • To transfer files using FTP there exist a version that uses a secure method of communication.
  • SFTP – Secure (Shell) File Transfer Protocol.
  • FTPS – which utilize Secure Socket Layer(SSL)/Transport Layer Security.

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secure connections3
Secure Connections
  • Various protocol and associated port;

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secure connections4
Secure Connections

Checkpoint:

  • SFTP and FTPS can be used in place of FTP.
  • SSH can be used in place of Telnet.
  • The SSH TCPport is 22.

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self study
Self Study
  • Application and Development Tools.
  • The Web Browser.

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