Introduction to Computing

Transcription

1 Introduction to Computing Engr. Abdul-Rahman Mahmood MS, PMP, MCP, QMR(ISO9001:2000) alphapeeler.sf.net/pubkeys/pkey.htm pk.linkedin.com/in/armahmood abdulmahmood-sss alphasecure mahmood_cubix VC++, VB, ASP

2 The Internet and the World Wide Web

3 In the beginning : Russians launch Sputnik. Eisenhower saw the need for the Advanced Research Projects Agency (ARPA) ARPA becomes a technological think-tank for American defence Several years later, ARPA starts looking into computer communication and networking 1962: ARPA appoints J. Licklider and L. Roberts to head its computer research program

4 In the beginning... ARPA 1962: ARPA appoints J. Licklider and L. Roberts to head its computer research program Focus on computer communication for military purposes Problem: Data traffic is bursty!

5 Packet Switching Data traffic is bursty intervals of activity followed by periods of inactivity. E.g. Think of a web browsing session Circuit switched networks would be inefficient Image Source: CEFRIEL, Milan

6 Packet Switching 1961: Leonard Kleinrock uses queuing theory, proposes packet switched networks More bandwidth efficient Robust not reliant on single route Image Source: Leonard Kleinrock's homepage,

7 ARPANET 1967: Lawrence Roberts of ARPA publishes plan for the first computer network system the ARPANET Packet switches were needed. Called Interface Message Processors (IMP), the contract was awarded to BBN Oct 1969: IMPs installed in UCLA Interface Message Processor Image Source:

8 Internetting principles Decentralized control Stateless routers Autonomy - networks should be independent, require no modification to participate in the Internet Best Effort Service Model - Packets would be routed through the fastest available route

9 The Internet s History 1969 ARPANET Developed by the Department of Defense Connected universities and defense bases 1973 ARPANET connects to Europe 2A-9

10 ARPANET A-10

11 1980s Time of tremendous growth Networks for linking universities together BITNET and ftp (Northeast) CSNET linking universities without access to ARPANET NSFNET: provide access to NSF supercomputing resources 1983: TCP/IP replaces NCP as universal host protocol on Jan 1. By the end of the 80s, there were 100,000 hosts

12 1990s...commercialization! NSFNET began to serve as backbone, linking regional networks in US and networks abroad ARPANET was decommissioned NSFNET was decommissioned in 1995, most Internet backbone traffic carried by commercial ISPs Increased commercialization, advent of WWW, all lead to explosion of growth

13 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 2A-13

14 1990s...commercialization! NSFNET began to serve as backbone, linking regional networks in US and networks abroad ARPANET was decommissioned NSFNET was decommissioned in 1995, most Internet backbone traffic carried by commercial ISPs Increased commercialization, advent of WWW, all lead to explosion of growth

15 Today and the Future 100,000 new web sites per month More than 50% of U.S. households online Access is available throughout the U.S. Eventually access will be global 2A-15

16 U.S. Internet Growth 2A-16

17 The Internet s Major Services The World Wide Web (WWW) 2A-17 Developed in 1993 by Tim-Berners Lee Required a browser to read documents The World Wide Web is a system of Internet servers that supportspecially formatted documents. The documents are formatted in a markup language called HTML (HyperText Markup Language) that supports links to other documents, as well as graphics, audio, and video files. This means you can jump from one document to another simply by clicking on hot spots. Not all Internet servers are part of the World Wide Web. Electronic mail ( ) Instantaneous transmission of documents

18 The Internet s Major Services News Often called newsgroups Electronic discussions on several topics File Transfer Protocol (FTP) Sends and receives files 2A-18

19 The Internet s Major Services Chat Public real time conversation Instant messaging Private real time conversation Peer-to-peer services Allows sharing of files among users Napster and Kazaa are examples Illegal to share copyrighted material 2A-19

20 Accessing The Internet Internet Service Provider (ISP) Company that provides Internet access Dialup Connects to Internet through phone line Modem connects to the phone line Slow connection 2A-20

21 Accessing The Internet High-speed access Connect through a special line 2 25 times faster than dialup DSL, Cable, T1 are common 2A-21

22 HTTP vs HTML HTML: hypertext markup language Definitions of tags that are added to Web documents to control their appearance HTTP: hypertext transfer protocol The rules governing the conversation between a Web client and a Web server Both were invented at the same time by the same person

23 The World Wide Web The Web An infrastructure of information combined and the network software used to access it Web page A document that contains or references various kinds of data Links A connection between one web page and another What are the links used for? 23

24 The World Wide Web Website A collection of related web pages Web browser A software tool that retrieves and displays eb pages Web server A computer set up to respond to requests for web pages 24

25 The World Wide Web Uniform Resource Locator (URL) A standard way of specifying the location of a Web page, containing the hostname, "/", and a file What is the relationship between the Internet and the Web? 25

26 The World Wide Web Why is the expression "visiting a website" confusing? 26

27 Search Engines Search Engine A website that helps you find other websites Can you name at least two? How do they work? 27

28 Weblogs Blog or Weblog An online journal or newsletter that is frequently updated and intended for public consumption Do you have a blog? Do you read blogs? 28

29 Cookies Cookie A small text file that a web server stores on your local computer s hard disk A cookie contains information about your visit to the site Cookies can be used to determine number of unique visitors to the site to customize the site for future visits to implement shopping carts that can be maintained from visit to visit Cookies are not dangerous 29

30 Understanding The Internet Browsers Read and translate the HTML Display web content Uniform Resource Locator (URL) Address of a web page 2A-30

31 Understanding The Internet Helper applications Plug-ins Enhance a browser s functionality Streaming audio and video Sends the file in small chunks Chunks downloaded while others play 2A-31

32 Streaming Audio 2A-32

33 Using a Browser And The WWW Browser starts on the home page Navigating the web Enter a URL in the browser Click a link Links are typically blue underlined words Image maps are picture links When finished, close the browser 2A-33

34 Searching the Web The Web is unorganized Directories Categorize the Internet Search engines Find sites by keyword 2A-34

35 Searching the Web Site searches Large sites have an internal search Metasearch sites Search several web sites at once Sponsored links Sites pay for better search results 2A-35

36 Search Techniques Quote the exact phrase Use the keyword AND Use the keyword NEAR Avoid common words Use the site s advanced tools 2A-36