The Internet, Intranets, and Extranets Chapter 7 The Internet, Intranets, and Extranets

The Internet The internet Internet networks A network of networks The internet transmits data from one computer (called a host) to another Internet networks Linked networks that work much the same way -- they pass data around in packets, each of which carries the addresses of its sender and receiver Schematic

Internet ‘Discussion’ (1) A global network connecting millions of computers. As of 1999, the Internet has more than 200 million users worldwide, and that number is growing rapidly. More than 100 countries are linked into exchanges of data, news and opinions. Unlike online services, which are centrally controlled, the Internet is decentralized by design. Each Internet computer, called a host, is independent. Its operators can choose which Internet services to use and which local services to make available to the global Internet community. Remarkably, this anarchy by design works exceedingly

Internet ‘Discussion’ (2) well. There are a variety of ways to access the Internet. Most online services, such as America Online, offer access to some Internet services. It is also possible to gain access through a commercial Internet Service Provider (ISP). Note: York University’s CCS (Computer and Communications Services) is an ISP.

How the Internet Works Transport control protocol (TCP) A protocol that operates at the transport layer and is used in combination with IP by most Internet applications Backbone An 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 computer E.g., http://www.yorku.ca/

Domain Affiliations Domain Affiliations arts cultural and entertainment activities com business organizations edu educational sites firm businesses and firms gov government sites info information service providers mil military sites nom individuals net networking organizations org organizations rec recreational activities store businesses offering goods for purchase web entities related to World Wide Web activities

Access to the Internet LAN servers Local 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 Internet Connection via an on-line service Examples are America Online and Microsoft Network. These services usually require sign-up procedures

Three Ways to Access the Internet Schematic

Internet Service Providers Internet service provider (ISP) Any company that provides individuals or companies with access to the Internet Thousands of providers including large communications companies Need an account with the ISP and software that links with TCP/IP

ISP Examples Internet Service Provider Web Address AT&T WorldNet Service www.att.com Digex, Inc. www.digex.net GTE Internetworking www.gte.net IBM Internet Connection www.ibm.net MCI Internet www.mci2000.com NetCom On-Line Communication Services www.netcom.com PSINet, Inc. www.psinet.com Sprint Internet Services www.sprint.net Uunet Technologies, Inc. www.us.uu.net

Internet Services E-mail Telnet FTP Usenet and newsgroups Chat rooms Internet phone Internet videoconferencing Content streaming

Selected Usenet Groups alt.fan.addams.family alt.life.itself alt.pets alt.fan.bevis-n-butthead alt.autos.camaro alt.fan.leonardo-dicaprio alt.cloning alt.history alt.fan.u2 alt.music.blues alt.sports.baseball.cinci-red alt.music.zz-top alt.politics.socialism alt.sports.college.sec alt.sports.soccer.european.uk

Internet Services Internet telephony Also called voice-over-IP (VOIP) Technology that enables network managers to route phone calls and fax transmissions over the same network they use for data

VOIP ‘Discussion’ Internet telephony is a category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls. For users who have free, or fixed-price, Internet access, Internet telephony software essentially provides free telephone calls anywhere in the world. To date, however, Internet telephony does not offer the same quality of telephone service as direct telephone connections. There are many Internet telephony applications available. Some, like CoolTalk and NetMeeting, come bundled with popular Web browsers. Others are stand-alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products.

Content Streaming Content streaming A method for transferring multimedia files over the Internet so that the data stream of voice and pictures plays continuously, without a break, or very few of them It also enables users to browse large files in real time

The World Wide Web World Wide Web A collection of tens of thousands of independently-owned computers that work together as one in an Internet service

WWW Terminology Home page Hypermedia Hypertext markup language (HTML) The cover page for a Web site that has graphics, titles, coloured text, etc. Hypermedia Tools that connect the data on Web pages, allowing users to access topics in whatever order they wish Hypertext markup language (HTML) The standard page description language for Web pages

Some Interesting Web Sites Says who? Library of Congress http://lcweb.loc.gov PointCast http://www.pointcast.com In-Box Direct http://www.netscape.com Online Career Center http://occ.com New York Times http://www.nytimes.com Project Gutenberg http://www.gutenberg.org Sportsline USA http://www.sportsline.com White House http://www.whitehouse.gov MIT Lab for Computer Science http://www.lcs.mit.edu The Wall Street Journal http://www.wsj.com

WWW Terminology Web browser Web page Applet Software that creates a unique hypermedia-based menu on your computer screen and provides a graphical interface to the Web Web page A screen of information sent to a requesting user and presented through a browser Applet A small program embedded in Web pages

HTML “The” language of WWW pages Need we say more!!!

Search Engines Search engines A search tool for the Web (like card catalogs in libraries) E.g., Altavista http://www.altavista.digital.com Excite http://www.excite.com Galaxy http://www.einet.net Hotbot http://www.hotbot.com Infoseek http://www.infoseek.com Lycos http://www.lycos.com Webcrawler http://www.webcrawler.com Yahoo! http://www.yahoo.com

Java Java An object-oriented programming language Developed by Sun Microsystems Based on C++ Allows small programs -- applets -- to be embedded within an HTML document

Applets Applets are small java programs that are downloaded from the server to the local machine

Push Technology Push technology E.g., Technology that enables users to automatically receive information over the Internet rather than searching for it using a browser Also called Webcasting E.g., PointCast InterMind

Webcasting ‘Discussion’ Using the Internet, and the World Wide Web in particular, to broadcast information. Unlike typical surfing, which relies on a pull method of transferring Web pages, webcasting uses push technologies.

Push ‘Discussion’ (1) In client/server applications, to send data to a client without the client requesting it. The World Wide Web is based on a pull technology where the client browser must request a Web page before it is sent. Broadcast media, on the other hand, are push technologies because they send information out regardless of whether anyone is tuned in. Increasingly, companies are using the Internet to deliver information push-style. One of the most successful examples of this is PointCast, which delivers customized news to users' desktops.

Push ‘Discussion’ (2) Probably the oldest and most widely used push technology is e-mail. This is a push technology because you receive mail whether you ask for it or not -- that is, the sender pushes the message to the receiver.

Business Use of the Web Uses: Applications, E-mail, Product Display, Catalogs, Order placement Products people are likely to buy on the Web Software 77% Books 67% CDs 64% Computer hardware 63% Airline tickets 61% Magazine subscriptions 53% Concert/theater tickets 48% Flowers 45%

Intranets and Extranets An internal corporate network built using Internet and World Wide Web standards and products that allows employees of an organization to gain access to corporate information Extranet A network based on Web technologies that links selected resources of the intranet of a company with its customers, suppliers, or other business partners

Intranet ‘Discussion’ A network based on TCP/IP protocols (an internet) belonging to an organization, usually a corporation, accessible only by the organization's members, employees, or others with authorization. An intranet's Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access. Like the Internet itself, intranets are used to share information. Secure intranets are now the fastest-growing segment of the Internet because they are much less expensive to build and manage than private networks based on proprietary protocols.

Extranet ‘Discussion’ A new buzzword that refers to an intranet that is partially accessible to authorized outsiders. Whereas an intranet resides behind a firewall and is accessible only to people who are members of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view. Extranets are becoming a very popular means for business partners to exchange information.

Firewall Firewall… A device that sits between your internal network and the outside Internet and limits access into and out of your network based on your organization’s access policy

Virtual Private Network (VPN) A secure connection between two points across the Internet Tunneling The process by which VPNs transfer information by encapsulating traffic in IP packets and sending the packets over the Internet Schematic

VPN ‘Discussion’ Short for virtual private network, a network that is constructed by using public wires to connect nodes. For example, there are a number of systems that enable you to create networks using the Internet as the medium for transporting data. These systems use encryption and other security mechanisms to ensure that only authorized users can access the network and that the data cannot be intercepted.

Tunneling ‘Discussion’ A technology that enables one network to send its data via another network's connections. Tunneling works by encapsulating a network protocol within packets carried by the second network. For example, Microsoft's PPTP technology enables organizations to use the Internet to transmit data across a virtual private network (VPN). It does this by embedding its own network protocol within the TCP/IP packets carried by the Internet. (Note: PPTP = point-to-point tunneling protocol) Tunneling is also called encapsulation.

Internet Issues Management issues Service bottlenecks No centralized governing body for the Internet Service bottlenecks Phenomenal growth has left a service void Providers underestimating computing power needed Reconciling router addresses needed to transverse the network

Privacy & Security Cryptography Encryption Digital Signature The process of converting a message into a secret code and changing the encoded message back to regular text Encryption The original conversion of a message into a secret code Digital Signature An encryption technique used for online financial transactions

Encryption software running on sending computer Have a nice day… Encryption software running on sending computer E%$&:”}{|… Decryption software running on Receiving computer Have a nice day…

Firewalls Firewalls Assured pipeline A method of preventing unauthorized access between a company’s computers and the Internet (looks at the header of a packet) Assured pipeline An Internet security method that looks at the entire request for data and then determines whether the request is valid

Firewall ‘Discussion’ (1) 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. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

Firewall ‘Discussion’ (2) There are several types of firewall techniques: Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing. Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation. Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking. Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

Firewall ‘Discussion’ (3) In practice, many firewalls use two or more of these techniques in concert. A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.

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