Internet*

Internet*Internet is the network of networks i.e. global network which make WWW (world wide web)

The InternetThe internetA network of networksThe internet transmits data from one computer (called a host) to anotherInternet networksLinked networks that work much the same way -- they pass data around in packets, each of which carries the addresses of its sender and receiver

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A network of networks, joining many government, university and private computers together and providing an infrastructure for the use of E-mail, bulletin boards, file archives, hypertext documents, databases and other computational resources

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History1968 - DARPA (Defense Advanced Research Projects Agency) contracts with BBN (Bolt, Beranek & Newman) to create ARPAnet1970 - First five nodes: UCLAStanfordUC Santa BarbaraU of Utah, and BBN1974 - TCP specification by Vint Cerf1984 On January 1, the Internet with its 1000 hosts converts en masse to using TCP/IP for its messaging

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Development of the Internet*1956USSR launches Sputnik, 1st satellite; USA Department of Defense (DOD) forms Advanced Research Projects Agency (ARPA)1962Packet-switched network concept1969DOD starts ARPANET for networking research1974Protocol for packet internetworking Transmission Control Program (TCP)1981BITNET (Because Its Time Network) provided widespread email access. Minitel is deployed across France by French Telecom

1982Internet Protocol (IP) established TCP/IP1984Domain Name Server (DNS) introduced and number of host is 1,0001986NSFNET created a high speed backbone (56Kbps) to interconnect supercomputer centers1987Number of hosts breaks 10,000

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*1989Number of hosts breaks 100,000 and NSFNET is upgraded to T1 line (1.544 Mbps)Commercial email carrier (Compuserve) connects to the Internet1990ARPANET ceases to exist; MCI mail connects to the Internet1991WAIS released by Thinking Machines Corporation to aid information searchGopher released by U of Minnesota

*1992WWW released by CERN (a physics research institute in Switzerland)Number of hosts breaks 1,000,000NSFNET upgraded to T3 line (44.736 Mbps)1993WWW annual growth rate 341,634%Whitehouse goes online president@whitehouse.gov United Nations & World Bank go on-line. US National Infrastructure Act championed by Al Gore.Mosaic developed by National Supercomputer Center

*1994NetscapeCommunities become wired to the Internet For example, Blacksburg, VA - bus & movie schedules on-line, town meetings, etc.US Senate and House go on-lineMass marketing frenzy on the InternetUSA sales at cybermalls grows to $200 million versus $50 billion in catalog sales & $1.5 trillion in total USA retail sales.1995*.com sites exceed *.edu sites1996Electronic commerce gets going seriously1998The government uses the Internet for public dissemination of information (or political assassination ) by publishing Starrs report on the Internet.

History*The Internet grew out of an experiment in the 1960s by the U.S. Department of Defense. The DoD wanted to create a computer network that would continue to function in the event of a disaster, such as a nuclear war. If part of the network was damaged or destroyed, the rest of the system still had to work. That network was ARPANET, (Advanced Research Projects Agency Network) which linked U.S. scientific and academic researchers. It was the forerunner of today's Internet.

The Creation of the InternetThe creation of the Internet solved the following challenges:Basically inventing digital networking as we know itSurvivability of an infrastructure to send / receive high-speed electronic messagesReliability of computer messaging

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Internet Growth Trends1977: 111 hosts on Internet1981: 213 hosts1983: 562 hosts1984: 1,000 hosts1986: 5,000 hosts1987: 10,000 hosts1989: 100,000 hosts1992: 1,000,000 hosts2001: 150 175 million hosts2002: over 200 million hostsBy 2010, about 80% of the planet will be on the Internet

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How the Internet WorksTransport control protocol (TCP)A protocol that operates at the transport layer and is used in combination with IP by most Internet applicationsBackboneAn Internet high-speed, long distance communications links (like a bus; wire that connects nodes)Uniform resource locator (URL)An assigned address on the Internet for each computerE.g., http://www.yorku.ca/

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Three Ways to Access the Internet*

Access to the InternetLAN serversLocal servers can provide access to the Internet through normal connections (e.g., Ethernet)Serial line internet protocol (SLIP) and Point-to-point protocol (PPP)Communications protocol software that transmits packets over telephone lines, allowing dial-up access to the InternetConnection via an on-line serviceExamples are America Online and Microsoft Network. These services usually require sign-up procedures

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*Net structure

The Web physically consists of your personal computer, web browser software, a connection to an Internet service provider, computers called servers that host digital data, and routers and switches to direct the flow of information.

*Web BrowserA web browser is the software program you use to access the World Wide Web, the graphical portion of the Internet. The first browser, called NCSA Mosaic, was developed at the National Center for Supercomputing Applications in the early 1990s. The easy-to-use point-and-click interface helped popularize the Web. Microsoft Internet Explorer and Netscape Navigator are the two most popular ones.

*Navigating the WebThe Web is known as a client-server system. Your computer is the client; the remote computers that store electronic files are the servers. To visit the website, enter the address or URL of the website in your web browser. Browser requests the web page from the web server that hosts the requested site. The server sends the data over the Internet to your computer. Your web browser interprets the data, displaying it on your computer screen.

*Navigating the WebThe "glue" that holds the Web together is called hypertext and hyperlinks. This feature allows electronic files on the Web to be linked so you can jump easily between them.Web pages are written in a computer language called Hypertext Markup Language or HTML.

*Web Addresses

World Wide Web is a network of electronic files stored on millions of computers all around the world. Hypertext links these resources together. Uniform Resource Locators or URLs are the addresses used to locate the files. Every URL is unique and identifies one specific file.example:http://www.du.ac.inThe home page of Delhi University.

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*Domain NamesEvery computer that hosts data on the Internet has a unique numerical address. For example, the numerical address for the White House is 198.137.240.100. But since few people want to remember long strings of numbers, the Domain Name System (DNS) was invented. DNS, a critical part of the Internet's technical infrastructure, correlates a numerical address to a word. To access the White House website, you could type its number into the address box of your web browser. But most people prefer to use "www.whitehouse.gov." In this case, the domain name is whitehouse.gov.

*The Structure of a Domain NameA domain name has two or more parts separated by dots and consists of some form of an organization's name and a three letter or more suffix. For example, the domain name for IBM is "ibm.com"; the United Nations is "un.org." The domain name suffix is known as a generic top-level domain (gTLD). It describes the type of organization.

Domain Affiliations*

DomainAffiliationsartscultural and entertainment activitiescombusiness organizationsedueducational sitesfirmbusinesses and firmsgovgovernment sitesinfoinformation service providersmilmilitary sitesnomindividuals netnetworking organizationsorgorganizationsrecrecreational activitiesstorebusinesses offering goods for purchasewebentities related to World Wide Web activitiesnetnetworking organizations

*Bookmarks and FavoritesBookmarks and Favorites save Web addresses so you can return to them quickly. To save a web page, go to the Bookmarks or Favorites menu or click on its icon and select Add. When you click on the icon again, the title of the page you recorded will appear at the bottom of the list. To access the page, just double-click on the title.

*TCP/IPTCP/IP ensures that messages are properly routed from sender to receiver and that these messages arrive intact.

UDP User datagram protocolWith UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths. UDP is sometimes called the Universal Datagram Protocol.

*The Internet architecture is based on the standard TCP/IP protocol, designed to connect any two networks which may be very different in internal hardware, software, and technical design. Once two networks are interconnected, communication with TCP/IP is enabled end-to-end so that any node on the Internet has the ability to communicate with any other no matter where they are.An IP address is a 32 bit long identifier that encodes a network number (or network prefix) and a host number192.168.11.2

Network AddressHost Address

Dotted Decimal notationIP addresses are written in a so-called dotted decimal notationEach byte is identified by a decimal number in the range[0..255]:Example

100000001001000010001001100011111st byte2nd byte3rd byte4th byte128.143.137.144*

*Packet SwitchingTCP = TRANSMISSION CONTROL PROTOCOL(Breaks messages into packetsand reassembles them)IP = INTERNET PROTOCOL(Moves packets aroundthe Internet)SOURCE: J. DECEMBER

*Protocolprotocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receiptIt is a set of rules and regulation.

HUBA common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

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PacketsA piece of a message transmitted over a packet-switching network. One of the key features of a packet is that it contains the destination address in addition to the data. In IP networks, packets are often called datagrams. *

Router A router is a networking device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers.

Cisco 1800 Router*

Nortel ERS 8600*

Search engineIndex..Web CrawlingBefore a search engine can tell you where a file or document is, it must be found. To find information on the hundreds of millions of Web pages that exist, a search engine employs special software robots, called spiders, to build lists of the words found on Web sites. When a spider is building its lists, the process is called Web crawling. (There are some disadvantages to calling part of the Internet the World Wide Web -- a large set of arachnid-centric names for tools is one of them.) In order to build and maintain a useful list of words, a search engine's spiders have to look at a lot of pages. *

Intorduction M.I.S.Intorduction M.I.S.*By: Dr. Y. Peter ChiuBy: Dr. Y. Peter ChiuIntorduction M.I.S.Intorduction M.I.S.*By: Dr. Y. Peter ChiuBy: Dr. Y. Peter ChiuIntorduction M.I.S.Intorduction M.I.S.*By: Dr. Y. Peter ChiuBy: Dr. Y. Peter ChiuIntorduction M.I.S.Intorduction M.I.S.*By: Dr. Y. Peter ChiuBy: Dr. Y. Peter Chiu