Unit-1 Introduction WWW

1. Unit-1 Introduction WWW Prepared by: Prof. Harish I Rathod Computer engineering department Gujarat power engineering & Research institute WEB APPLICATION DEVELOPMENT (170705)

2. 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)”. GPERI – WAD - UNIT-1

3. 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). GPERI – WAD - UNIT-1

4. 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. GPERI – WAD - UNIT-1

5. 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. GPERI – WAD - UNIT-1

6. The INTERNET and The WWW • The Basic Idea behind IP addressing. GPERI – WAD - UNIT-1

7. 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. GPERI – WAD - UNIT-1

8. 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. GPERI – WAD - UNIT-1

9. The INTERNET and The WWW • OSI Model. GPERI – WAD - UNIT-1

10. The INTERNET and The WWW • Internet Layered (TCP/IP) Model. GPERI – WAD - UNIT-1

11. 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. GPERI – WAD - UNIT-1

12. 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. GPERI – WAD - UNIT-1

13. 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. GPERI – WAD - UNIT-1

14. 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. GPERI – WAD - UNIT-1

15. 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. GPERI – WAD - UNIT-1

16. 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. GPERI – WAD - UNIT-1

17. 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. GPERI – WAD - UNIT-1

18. 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? GPERI – WAD - UNIT-1

19. 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. GPERI – WAD - UNIT-1

20. Protocols And Programs File: >ftp mysuperserver.co.uk Connected to mysuperserver.co.uk 220 FTP Server ready Name : abc Password: ftp>put myIndex.doc GPERI – WAD - UNIT-1

21. 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 GPERI – WAD - UNIT-1

22. 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 GPERI – WAD - UNIT-1

23. 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). GPERI – WAD - UNIT-1

24. 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. GPERI – WAD - UNIT-1

25. 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. GPERI – WAD - UNIT-1

26. 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). GPERI – WAD - UNIT-1

27. 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. GPERI – WAD - UNIT-1

28. 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. GPERI – WAD - UNIT-1

29. 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. GPERI – WAD - UNIT-1

30. 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), GPERI – WAD - UNIT-1

31. 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 GPERI – WAD - UNIT-1

32. 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. GPERI – WAD - UNIT-1

33. 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 GPERI – WAD - UNIT-1

34. 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 GPERI – WAD - UNIT-1

35. 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 GPERI – WAD - UNIT-1

36. 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 GPERI – WAD - UNIT-1

37. 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 GPERI – WAD - UNIT-1

38. 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 GPERI – WAD - UNIT-1

39. 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 GPERI – WAD - UNIT-1

40. Protocols And Programs Web Pages: • Types of error code: • 404 = Not found. • 401 = Unauthorized. • 500 = Internal server error. • 501 = Not implemented. GPERI – WAD - UNIT-1

41. 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. GPERI – WAD - UNIT-1

42. 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. GPERI – WAD - UNIT-1

43. 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. GPERI – WAD - UNIT-1

44. Secure Connections • Various protocol and associated port; GPERI – WAD - UNIT-1

45. 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. GPERI – WAD - UNIT-1

46. Self Study • Application and Development Tools. • The Web Browser. GPERI – WAD - UNIT-1