Lecture 3
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The document provides an overview of the internet and its key components. It discusses how the internet originated from the ARPANET project in 1968 and evolved to become a global system of interconnected computer networks using TCP/IP. The key elements that enable the internet are described, including protocols like TCP and IP, packets, routers, domain names, HTML, email and the World Wide Web. Common internet services like file transfer, communication tools, information retrieval and e-commerce are also summarized. Connection types, firewalls and other networking concepts are briefly covered as well.
Lecture 3
- 2. Internet
- 3. What is Internet? 15-Jul-17 3 The internet or Internet is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link devices worldwide. A computer network is any set of computers or devices connected to each other with the ability to exchange data. Internet were planted in 1968 when US Department of defense sponsored a project name ARPANET (Advance Research Projects Network). Internet is a global network of networks which either uses the TCP/IP protocol or are able to interact with TCP/IP networks via gateways and provides users with electronic mail messaging, remote login, file transfer, network news the www etc. The internet offers access to data, graphics, sound, software, text and people through a variety of services and tools for communication and data exchange.
- 5. Computer Network Layered Architecture 15-Jul-17 5
- 6. Types of Computer Networks 15-Jul-17 6 Local Area Network (LAN): A small network constrained to a small geographic area like a home, office, or group of buildings e.g. a school. Wide Area Network (WAN ): A larger network that covers a large geographic area. WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations. Metropolitan Area Network (MAN): A network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN. Wireless Local Area Network (WLAN): A type of local area network (LAN). Personal area network (PAN): A computer network organized around an individual person within a single building. Storage area network (SAN) Virtual private network (VPN )
- 7. Intranet vs. Extranet 15-Jul-17 7 Intranets and Extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. Intranet: A local or restricted communications network, especially a private network created using World Wide Web. It may consist of many interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet includes connections through one or more gateway computers to the outside Internet. Gateway: A gateway is a network node (router) that connects two networks using different protocols together. Extranet: An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities.
- 8. World Wide Web 15-Jul-17 8 The World Wide Web is by far the most exciting and diverse part of the Internet. The World Wide Web (commonly shortened to the Web ) is a system of interlinked hypertext documents accessed via the Internet. World Wide Web was created in 1989 by Sir Tim Berners-Lee, working at CERN in Geneva, Switzerland. WWW is a set of programs standards and protocols that allow the multimedia and hypertext files to create, display and linked on the internet. From the late 1960 to early 1990 the internet was a communications and research tool used almost exclusively for academic and military purpose This changed radically with the introduction of the World Wide WEB.
- 9. HTML 15-Jul-17 9 HTML (Hypertext Markup Language) is the language used by the web pages in the World Wide Web. "Hypertext" refers to links that connect webpages to one another, either within a single website or between websites. HTML markup includes special "elements" such as <head>, <title>, <body>, <header>, <footer>, <article>, <section>, <p>, <div>, <span>, <img>, and many others.
- 10. Key Components of The Internet 15-Jul-17 10 TCP: Transmission control protocol (TCP) was first introduced in 1974. TCP messages were messages that were encapsulated, and then de-capsulated, kind of like how a letter is placed in an envelope. It focused on the reliability of networks to make sure that the messages and information being transferred would arrive safely. Modem: Connects your computer to an Internet service provider. IP Address: Used to identify computers. Packets: Information being transmitted through the Internet is broken up into small packets. Routers: Routers are the devices that transfer packets from one computer to another. They ensure that the packets reach their destination quickly and efficiently. Domain Names: Domain names refer to specific computers or organizations on the Internet. They specify the location of websites such .au->(Australia), .ca->(Canada) etc. WWW HTML E-mail
- 11. Internet Services 15-Jul-17 11 Internet Services Communication Services Information Retrieval Services Web Services Word Wide Web
- 12. Communication Services 15-Jul-17 12 E-mail: Used to send electronic message over the internet. Telnet: Used to log on to a remote computer that is attached to internet. Newsgroup: Offers a forum for people to discuss topics of common interests. Internet Relay Chat (IRC): Allows the people from all over the world to communicate in real time. Mailing Lists: Used to organize group of internet users to share common information through e-mail. Internet Telephony (VoIP): Allows the internet users to talk across internet to any PC equipped to receive the call. Instant Messaging: Offers real time chat between individuals and group of people. Example: Yahoo messenger, MSN messenger, Hangout etc.
- 13. Information Retrieval Services 15-Jul-17 13 File Transfer Protocol (FTP): Enable the users to transfer files. Archie: It’s updated database of public FTP sites and their content. It helps to search a file by its name. Gopher: Used to search, retrieve, and display documents on remote sites.
- 14. Web Services 15-Jul-17 14 Web services allow exchange of information between applications on the web. Using web services, applications can easily interact with each other.
- 15. File Transfer Protocol (FTP) 15-Jul-17 15 File Transfer Protocol (FTP) is a standard Internet protocol for transmitting files between computers on the Internet over TCP/IP connections. FTP was originally defined in 1971, prior to the definition of TCP and IP, and has been redefined many times. A good example of how FTP is used today is by web developers, who will connect to their web server using FTP and send updated versions of their web pages to the server. Although many FTP servers require logins, many FTP servers also allow anonymous FTP login, which only require a username and e-mail with no password. FTP is insecure. Username and password are sent to the server they're both sent as plaintext and could be intercepted and read.
- 16. File Transfer Protocol (FTP) 15-Jul-17 16
- 17. E-Mail 15-Jul-17 17 Email (electronic mail) lets you type and send a message to anyone, anywhere in the world who has an Internet connection and an email account. Just like a regular letter, except it’s electronic. There are two parts to an e-mail message: Header, Body. Header: The header of an e-mail message contains the name and the e-mail address of the recipient of the message, as well as the message’s subject. If you are sending the message to more than one person, the header will contain the names and addresses of all the people you are sending it to. Body : The body of an e-mail message is the message itself. A typical e-mail address might look like : abc@gmail.com CC (Carbon Copy): To send a copy to a second person but don't want to address them directly, click here and write their Email address, they will receive their carbon copy at the same time as the recipient.
- 19. E-Commerce 15-Jul-17 19 E-commerce (electronic commerce or EC) is the buying and selling of goods and services, or the transmitting of funds or data, over an electronic network, primarily the internet. The beginnings of e-commerce can be traced to the 1960s, when businesses started using Electronic Data Interchange (EDI) to share business documents with other companies. E-commerce is conducted using a variety of applications, such as email, online catalogs and shopping carts, File Transfer Protocol, and web services. More companies now try to entice consumers directly online, using tools such as digital coupons, social media marketing and targeted advertisements. The benefits of e-commerce include its around-the-clock availability, the speed of access, the wide availability of goods and services for the consumer, easy accessibility, and international reach. Examples: eBay, amazon, flipkart etc.
- 21. Electronic Meeting Systems 15-Jul-17 21 Group meeting software platform that provides electronic features that facilitates participation, problem-solving and decision-making. The unique features of EMS systems overcome the limitations of traditional face-to-face meetings such as lack of participation, criticism and domination of the proceedings by a few members. Types: Audio Conferencing Video Conferencing Computer Conferencing
- 24. Internet Connection Type 15-Jul-17 24 Dial-up: Dial-up access is a form of Internet access via telephone line. The client uses a modem connected to a computer and a telephone line, to dial an Internet service provider's (ISP) node to establish a modem-to-modem link, which is then routed to the Internet. DSL ( Digital subscriber line): DSL, which stands for Digital Subscriber Line, uses existing 2- wire copper telephone line connected to one’s home so service is delivered at the same time as landline telephone service. Customers can still place calls while surfing the Internet. Broadband wireless access: Wireless Broadband is a technology that provides high-speed wireless internet and data network access over a wide area. Satellite: In certain areas where broadband connection is not yet offered, a satellite Internet option may be available. Similar to wireless access, satellite connection utilizes a modem. ISDN: Integrated Services Digital Network allows users to send data, voice and video content over digital telephone lines or standard telephone wires. The installation of an ISDN adapter is required at both ends of the transmission—on the part of the user as well as the Internet access provider. Cable modem: A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure.
- 25. Firewall 15-Jul-17 25 A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. The term firewall originally referred to a wall intended to confine a fire or potential fire within a building. Firewall technology emerged in the late 1980s when the Internet was a fairly new technology in terms of its global use and connectivity