Introduction to the Internet & Web PDF

CHAPTER 1: INTRODUCTION TO THE INTERNET AND THE WEB FBI 101 Web Development WHAT IS THE INTERNET?  The Internet is the world’s largest computer network which interconnects millions of businesses, government agencies, educational institutions, and individuals networks in one cohesiv...

CHAPTER 1: INTRODUCTION TO THE INTERNET AND THE WEB FBI 101 Web Development WHAT IS THE INTERNET?  The Internet is the world’s largest computer network which interconnects millions of businesses, government agencies, educational institutions, and individuals networks in one cohesive unit.  Through the Internet, society have access to global information and instant communications anytime and anywhere. HISTORY OF THE INTERNET  Developed by US academic institutions and funded as a research network by US defense agencies.  The initial network was built in 1969 under the name ARPANET (Advanced Research Projects Agency Network) with just 4 computers linked together.  In the early 1970s it was recognized that there was a need to develop a standard Internet protocol for connecting together the diverse technologies that were being experimented with. This protocol is now known as Internet Protocol (IP) and is still in use.  Evolution of the Internet 4 1986 NSF connects NSFnet to 1969 ARPANET and ARPANET becomes 1996 becomes known as the Internet2 is functional Internet founded 1984 1995 NSFNet Today More ARPANET has terminates its than 550 more than network on million hosts 1,000 the Internet connect to the individual and resumes Internet computers status as linked as research hosts network Pages 75 - 76 HISTORY OF THE INTERNET  The data packets of IP are datagrams which are analogous in concept to a postal letter or a telegram. In IP each packet of data is independent of all other packets just as each postal letter is independent.  A problem with the IP datagram protocol is that it can lose data in transit over the Internet or deliver it in a different order from the order sent - both of which are unacceptable to most applications. Circuit Switch  Used for phone call  Electronic signals pass through several switches before a connection is established. And during a call, no other network traffic can use those switches.  Example of circuit-switching: You pick up your land phone and dial your friend. At that point, the Telco provider creates a dedicated circuit for that session and connects you to your friend's telephone. No matter how long you keep the line open with your friend, the circuit will remain, and packets flowing between both telephones will always follow the same path. This is an example of a circuit-switched network. Packet Switch  Packet-switched networks move data in separate, small blocks(packets) based on the destination address in each packet.  When received, packets are reassembled in the proper sequence to make up the message.  Example of packet-switching: In the second example, you switch on your PC and connect to your favourite site that offers a number of applications you can download from, so you begin downloading one application at a time. Each packet has to find its own route to the destination, i.e., your computer. Each packet finds its way using the information it carries, such as the source and destination IP address. If network congestion occurs, the routers responsible for routing packets between networks will automatically select different paths to ensure data is transferred as required. Circuit-switched v. Packet-switched Networks 1-8 HISTORY OF THE INTERNET  A second standard protocol was developed in the 1970s called Transmission Control Protocol (TCP). TCP establishes a logical connection from source to destination over which a numbered sequence of packets may flow.  Cerf and Kahn design TCP/IP protocol (Dividing messages in to packets at the sending computer and reassembling the packets at the receiving computer) What is the Internet?  Benefits:  Communicating  Accessing & Sharing Information  Shopping  Banking & Investment  Entertainment and leisure The Internet  Internet service provider (ISP) is an organization, such as a cable company or a telephone company, that supplies connections to the Internet for a monthly fee. What is computer network?  Is a collection of computers and devices connected together, via communications devices and transmission media, allowing computers to share resources. Computer networks PC Mobile network server Global ISP wireless laptop cellular Home network handheld Regional ISP access points Institutional network wired links router Classification of Networks Area of coverage:  Local Area Network (LAN) – limited geographical area – e.g home, lab, office  Metropolitan Area Network (MAN) – connect LANs in metropolitan area – e.g city, town  Wide Area Network (WAN) – covers large geographical area – e.g city, country, world (the internet is the largest WAN) Classification of networks Architecture of networks  Client-server A server is any computer that accepts requests from other computers that are connected to it and share some or all of it resources (files, printers, programs) with those computers. The clients are other computers or devices on the network that rely on the server for its resources. Architecture of networks  Peer-to-peer ▪ Each computer,called a peer, has equal responsibilities and capabilities, sharing hardware (such as a printer), data, or information with other computers on the peer- to-peer network. Each computer stores files on its own storage devices. Thus, each computer on the network contains both the server operating system and application software.  Architecture of networks Client / Server Peer-to-Peer Network: Communication Devices  Dial-up Modems: A dial-up modem is a communications device that can convert digital signals to analog signals and analog signals to digital signals, so that data can travel along an analog telephone line. (e.g. fax machine is connecting to dial-up modems)  Cable Modems: sometimes called a broadband modem, is a digital modem that sends and receives digital data over the cable television. Network: Communication Devices  ISDN and DSL Modems: An ISDN modem sends digital data and information from a computer to an ISDN line and receives digital data and information from an ISDN line. A DSL modem sends digital data and information from a computer to a DSL line and receives digital data and information from a DSL line.  Wireless Modem  Network cards  Wireless Access Points  Routers Wireless Access Point & Router Network: Transmission Media Physical:  Twisted-Pair Cable: The wires are twisted together to reduce noise. (e.g. LAN cable)  Coaxial Cable (e.g. Cable television (CATV) network wiring)  Fiber-Optic Cable Wireless:  Infrared  Broadcast Radio (e.g. Bluetooth, UWB, Wi-Fi, and WiMAX, communications technologies)  Cellular Radio (e.g. wireless modems and cell phones) Network: Transmission Media  Microwaves: Microwave transmission, often called fixed wireless, involves sending signals from one microwave station to another using line-of-sight transmission. Normally used in wide- open areas such as deserts or lakes, between buildings in a close geographic area, or to communicate with a satellite. Network: Transmission Media  Communication Satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations. How to identify devices in the Internet?  Internet Protocol address (IP address)  Domain names  Host machines.domain names  ucsi.edu.my  Mid 80’s a collection of different protocols with its own user interface proliferate i.e. telnet, FTP, Usenet, mailto  User has to learn to use it  SOLUTION: WWW  Other Internet Services 26  FTP (File Transfer Protocol) is an Internet standard that permits file uploading and downloading with other computers on the Internet  Many operating systems include FTP capabilities  An FTP server is a computer that allows users to upload and/or download files using FTP Click to view Web Link, click Chapter 2, Click Web Link from left navigation, then click FTP below Chapter 2 Page 107  Evolution of the Internet 27  An IP address is a number that uniquely identifies each computer or device connected to the Internet  A domain name is the text version of an IP address  Top-level domain (TLD)  A DNS server translates the domain name into its associated IP address Pages 79 – 80 Figure 2-4 Doman Name http://www.nps.gov/grsm/planyourvisit/wildlifeview.html Ptotocol Domain Name Path Webpage Name World Wide Web (WWW)  Also call the Web, and it is one of the most popular service on the Internet.  Contains billions of worldwide collection of electronic documents called web pages.  A web page can contain text, graphics, audio, and video, and as built-in connections, or links, to other web documents.  A website is a related collection of web pages (e.g.: UCSI website). World Wide Web (WWW)  The most common protocol is the hypertext transfer protocol, HTTP which provides a standard form of communication between web browsers and web servers.  A Web server is a computer that delivers requested Web pages to your computer. ❑ Hypertext is text displayed on a computer with references to other text that reader can immediately access. ❑ Hypermedia is a nonlinear medium of information that includes graphics, audio, video, plain text and hyperlinks.. Web 2.0  Web 2.0 describes World Wide Web sites that use technology beyond the static pages of earlier Web sites. A Web 2.0 site may allow users to interact and collaborate with each other in a social media dialogue as creators of user-generated content in a virtual community.  Web 2.0 sites allow users to do more than just retrieve information. Instead of merely 'reading', a user is invited to 'write' as well, or contribute to the content available to everyone in a user friendly way.  Example of web 2.0: Cloud computing, social networking sites, blogs, wikis, folksonomies, video sharing sites, hosted services, Web applications, and mashups. Web 3.0  The most important features are the Semantic Web and personalization.  The Semantic Web is a collaborative movement led by international standards body the World Wide Web Consortium (W3C). The standard promotes common data formats on the World Wide Web.  The Semantic Web is regarded as an integrator across different content, information applications and systems.  The collection, structuring and recovery of linked data are enabled by technologies that provide a formal description of concepts, terms, and relationships within a given knowledge domain. Web Browser  Programs running on client machines  Request for documents using URL  The World Wide Web 34 Page 81 Figure 2-6  The World Wide Web 35  There are thirteen types of Web sites Portal News Informational Business/Marketing Blog Wiki Online Social Educational Network Pages 88 – 91 Figure 2-15  The World Wide Web 36 Entertainment Advocacy Web Application Content Personal Aggregator Pages 91 – 92 Figure 2-15 Web Server  A computer that provide web pages to requesting browser.  Delivers the content using the HTTP, over the WWW.  URL (Uniform Resource Locator)  A unique address for a web page.  Used to identify web pages on the internet.  URL Format  scheme:object-address A communication protocol Fully qualified domain name/path to document  how://where/what  :///