Information and Communication Technology Fundamentals

1. Information and Communication Technology Fundamentals Credits Hours: 2+1 Instructor: Ayesha BintSaleem

2. NETWORKS - III

3. Presentation Credits • “Introduction to Computer” by Peter Norton • “Using Information Technology” by Williams and Sawyer • “Introduction to Information Technology” by V. Rajaraman

4. The Internet’s History • 1969 – ARPANET • Developed by the Department of Defense • Connected universities and defense bases • 1973 – ARPANET connects to Europe

5. ARPANET 1973

6. The Internet’s History • Mid-1980s – NSFNet • Network between supercomputers • Internet was the link to ARPANET • No commercial traffic allowed • 1990s • ARPANET shut down • NSFNet abandoned • Commercial networks take over

7. Today and the Future • Thousands of networks • Hundreds of millions of users • Huge co-operative community with no central ownership • Anybody can access it

8. The Internet’s Major Services

9. 1. E-mail • Stands for electronic mail • One of the “killer application” for the internet • Use E-mail client • E.g. outlook express • Web based email service

10. E-mail (contd) • E-mail addresses • ayesha.saleem@niit.edu.pk • Unique id • Email server • Or email service provide e.g hotmail.com

11. E-mail (contd) • Mail Server • When you send an email, message is stored on email server, until the recipient can retrieve it • Many mail server use Post Office Protocol (POP) • Also called POP servers • Internet Message Access Protocol (IMAP) • Used by local clients to retrieve email from email servers

12. E-mail (contd) • Mail Server • Simple Mail Transfer Protocol (SMTP) • Used by mail servers to send/receive messages

13. E-mail (contd) • E-mail features • Audio, Video, Images can be sent as attachment • Reply, Reply All, Forward, Delete, CC, BCC • Listserv • Lists of e-mail addresses • Each address gets the e-mail

14. Spam: Unwanted Junk E-Mail Delete without opening the message Never reply to a spam message!

15. 2. Information Browsing • “To retrieve and display specified information stored in one or more computers connected to a computer network” • Implies interactivity

16. Menu Based Browsing • Earliest browsers were menu based • Gopher • Menu is presented • User selects a menu item • Gopher software will search table to find out where the required information is stored • May be on another computer • Retrieve information and display • Look up process hidden from user

17. Hypertext Based Browsing • A system in which documents scattered across many Internet sites are directly linked, so that a word, phrase or an image in one document becomes a connection to a document in a different place • User clicks a word/image • Document is retrieved

18. Hypertext Based Browsing (contd) • Hypertext systems provide an easy way to manage large collections of data scattered world wide • Documents can be interconnected • Facilitates non-linear reading

19. World Wide Web • Billions of documents, stored in different places, linked together in some manner • “Web” of interconnected information • Collection of documents and links spread all over globe • “World wide web” • Developed in 1993 by Tim-Berners Lee

20. How the web works? • HyperText Transfer Protocol (HTTP) • Special protocol used by web to supports hypertext documents • HyperText Markup Language (HTML) • Hypertext documents are encoded in HTML • A notation to mark keywords in documents • Allows author to embed hypertext links

21. How the web works? (contd) • Uniform Resource Locator (URL) • Method of naming documents or places on the Websites • String of characters that identifies • the type of document, • the computer the document is on, • the directories and subdirectories the document is in, and • the name of the document.

22. How the web works? (contd) • Uniform Resource Locator (URL) (contd) http://www.nps.gov/abli/index.htm • Protocol : http • Domain name: www.nps.gov • Directory name: abli • File name: index.htm

23. How the web works? (contd) • Hypertext Browser • Marc Anderson developed Mosaic web browser • Some popular browsers today are • Internet Explorer • Firefox • Netscape communicator (successor to Mosaic) • URLs can be typed in a browser

24. How the web works? (contd) • Web pages and Websites • A hypertext document is called a web page • Collection of related web pages is a website • A Web page is a document on the World Wide Web on a Website that can include text, pictures, sound, and video

25. How the web works? (contd) • Helper Applications • Many websites feature multimedia content • Browsers alone cannot display every type of content • Multimedia files requires special applications in order to be played in real time • Also called plug-in applications

26. How the web works? (contd) • Helper Applications (contd) • Plug-ins support several types of content including audio and video streaming • Content is sent in a continuous stream (still in packets) from web server to browser • Plug-in receives first portion and buffers it • First portion is played while next portion is buffered

27. Streaming Audio

28. Some Common Plug-ins

29. Searching the World Wide Web • The Web is unorganized • Directories • Categorize the Internet • Search engines • Find sites by keyword

30. Searching the World Wide Web • Resource Directories • Directory separates subjects in categories • Typically employ human experts

31. Resource Directory

32. Searching the World Wide Web • Search Engine • Search using keywords • E.g. Google.com • Offer advanced options as well • Do not use humans to index documents • Automated programs called “web crawlers” • browse world wide web in a systematic manner • Pick keywords • Create index

33. Searching the World Wide Web • Meta Search Engine • Uses multiple search engines simultaneously to lookup your keyword • Searhenginewatch.com • News about different search engines

34. Other Internet Features • File Transfer Protocol (FTP) • Allows you to access any computer connected to the internet and download files • FTP Site is a collection of files housed on an FTP Server ftp://ftp.xcollege/admission-rules • Remote server, ftp.xcollege, will prompt for a login id and password • Public FTP archives accept “anonymous” as user id

35. Other Internet Features • Telnet • Logging on to a remote computer and using its facilities • telnet: <domain name of computer> or IP address • Login ID and Password

36. Other Internet Features • Internet Relay Chat (IRC) • Real time communication system • Multi-users with many channels (rooms) • Channels are dedicated to a topic • All users can read the comments

37. Other Internet Features • Instant messaging (IM) • Private, real-time communication • Message sent only to listed users • Buddy lists contain IM names

38. Other Internet Services • Peer-to-peer (P2P) services • User computers are connected together • No centralized organization • Users can communicate directly • Users can share files

39. Other Internet Services • Internet Radio • Audio from radio station is stored in high speed disk memory of server • Person wishing to listen to broadcast logs on to the server and listens to it by downloading it using internet • Intermittent reception due to packet switching • Start with delay

40. Other Internet Services • Internet Telephony • Normal telephony is circuit switched • Expensive • Talk over packets • Low cost • Quality may not be the best • Voice over IP (VoIP)

41. Other Internet Services • Video Conferencing • Voice + Video over Internet • Different standards exist