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Introduction to Web Technology

Introduction to Web Technology. SWE 444 . Internet and Web Application Development. Dr. Ahmed Youssef. Internet. It is a network of networks connected and communicating using TCP/IP communication protocol. Computer Networks. Brief History of the Internet.

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Introduction to Web Technology

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  1. Introduction to Web Technology SWE 444 Internet and Web Application Development Dr. Ahmed Youssef

  2. Internet It is a network of networks connected and communicating using TCP/IP communication protocol

  3. Computer Networks Ahmed Youssef:: SWE444: Internet and Web Application Development

  4. 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

  5. A Brief Summary of the Evolution of the Internet ??? Assignment

  6. 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

  7. Intranet & Extranets

  8. Intranet & Extranets Ahmed Youssef:: SWE444: Internet and Web Application Development

  9. Components of Web • Web Page and Web Site • Web Browsers and Web Servers • Uniform Resource Locator(URL) • HTML • HTTP • Internet Protocol

  10. 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

  11. It's a software It lets you visit webpages and use web applications Types: Internet Explorer Mozilla Firefox Netscape Navigator Google Chrome Opera … Web Browser

  12. 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.

  13. Accessing a web site

  14. HTMLHyperText 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:: SWE444: 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:: SWE444: Internet and Web Application Development 15

  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 16

  17. Client Server Server Request Response Client Client Client

  18. Client Program Server Program Client PC Client/Server Computing Client/Server Processing with Request-Response Cycle Request Message Response Message File Server

  19. Client is Browser Server Program Web-Enabled Application HTTP Request Message HTTP Response Message Web-enabled applications: Form of client server processing that uses browsers as clients. Client PC E-Mail Server

  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.

  21. 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 IPv4) • 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? Establish connection. OK. Can I talk to you? OK. { Here’s a packet. Send packet with acknowledgment. Got it. { Here’s a packet. Resend packet if no (or delayed) acknowledgment. Here’s a resent packet. Got it.

  24. Uniform Resource Locator 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 24

  25. 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

  26. Example http://www.uoh.edu.sa/a.khedr/swe444.html Transfer Protocol: Server name: Directory Path: File name: Ahmed Youssef:: SWE444: Internet and Web Application Development 26

  27. 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

  28. 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:: SWE444: Internet and Web Application Development

  29. 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

  30. Types of web sites based on content • Information • Search Engines • Educational • Forums • Company • Online shops • … Ahmed Youssef:: SWE444: Internet and Web Application Development

  31. 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 • Hyper Text Mark-up Language (HTML) • Hyper Text Transport Protocol (HTTP) • Uniform Resource Locators (URLs)

  32. 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 Server Client Browser Web Server 1. HTTP request for image 2. HTTP response containing image 3. Store image Cache

  35. Client Caching Server Client Browser Web Server This… HTTP request for image HTTP response containing image I need that image again… Cache

  36. Client Caching Server Client Browser Web Server I need that image again… Getimage … or this Cache

  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 I’d like to talk securely to you (over port 443) Browser TLS/SSL TLS/SSL Web Server HTTP Requests Here’s my certificate and encryption data HTTP Requests Here’s an encrypted HTTP request Here’s an encrypted HTTP response Here’s an encrypted HTTP request HTTP Responses HTTP Responses Here’s an encrypted HTTP response

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