|
Describe how hardware, protocols, and software work together to create the Internet Compare and contrast the types of communication tools available on the Internet
|
| Sana | 24.12.2019 | | Hajmi | 54.32 Kb. | | #4718 |
Chapter 4: The Internet
and World Wide Web Succeeding with Technology: 2005 Update Edition Objectives Describe how hardware, protocols, and software work together to create the Internet Compare and contrast the types of communication tools available on the Internet Explain the underlying structure of the Web and the technologies that support it Define the categories of information and services that the Web provides and the ways in which the Web supports research 1880s – 1950s – Telegraph, telephone Global, public network – nearly all voice or coded voice Through 1980s Data communication used the telephone network Rent your own dedicated circuit, point A to point B “Switch-based” – to save costs, telephone companies developed switching systems to re-use wire circuits Today (2005) More players – telephone systems, cable TV systems, satellite communication systems, “roll your own” (e.g. “dark fiber”) Roles are reversing and merging other networks are now carrying telephone (e.g. cable, Internet) telephone is carrying Internet data, video (e.g. cell phones) A Brief History of the Internet 1960s – AlohaNet – first radio packet switching data network. Used to link Hawaiian islands. 1969 - ARPA commissioned ARPANET for research into networking 1980s – commercial communication satellites, TCP/IP, expansion of ARPANET to Internet 1990s – explosion of cellular phones, Internet, and cable broadband services 2000s – competitition/integration/consolidation of communication technologies
How Does the Internet Work? Packet-switching – data broken up into packets, header of each contains address, sequencing information each packet travels independently across the network, may arrive out of sequence receiving end re-assembles packets into original data Internet backbone High-speed communication lines to which regional ISPs connect Internet service providers (ISP) Provide users with access to the Internet
Protocols Are At Each Layer Advantages of Layers Divides up responsibilities Reduces duplication of function Faster processing, lower maintenance cost Disadvantages More complex, takes more time to make major changes – e.g. IPv6
Internet Layers Hardware layer Receives data from physical media, hands it off to Transport layer MAC (Media Access Control) address, Hardcoded into each network interface card (NIC) E.g. 00-C0-4F-04-67-21 – each manuf. Is assigned a unique range Internet Layers Transport layer Breaks messages into packets, adds MAC address and sequence to each, re-assembles at the other end, checks if message is correct and complete TCP – Transport Communication Protocol – acknowledges receipt, checks if message is complete UDP – User Datagram Protocol aka “Unreliable Data Protocol” – no acknowledgment, leaves checking to the other layers - faster, better when data reliability is not as important as speed – e.g. VoIP Relies on broadcasting to send its messages – “anybody this applies to, pick up…” therefore NOT good for more than a few hundred devices without… Internet Protocols Internet Layer – handles communication between networks Forwards packets whichever way seems most efficient according to a ROUTING TABLE Keeps track of traffic according to IP ADDRESS E.g. 169.226.x.x is within the albany.edu “domain” (Router) Forwards anything not addressed to 169.226 to the Internet Receives data from physical media, hands it off to Transport layer, including MAC address from the Ethernet card Summary of Internet Addressing
Application layer addressing, depends upon the application Email – rdg28@albany.edu File transfer – rdg28@itsunix.albany.edu/public_html/isp611 Telephone - 518-452-1407 Host address – www.albany.edu
Transport layer addressing MAC address – hardcoded in the NIC card e.g. 01-24-57-9a-bd-f2 Internet layer addressing IP address – e.g. 169.226.x.x
Physical layer addressing MAC or device number or channel (e.g. wireless) Application Layer, Protocols Email Bitnet (pre-Internet) – store and forward whole email messages from one mainframe to the next via telephone lines SMTP – Simple Mail Transfer Protocol MAPI – protocol for attachments to email POP – enable automatic download to PC IMAP – keep mail on a server, access from anywhere Character-based login – TELNET File transfer – FTP
To Each Application, Its Protocols Instant messaging aka “Chat” – IRC, AOL IM, ICQ IM, Yahoo IM, Windows IM Network news – NNTP, Usenet Audio/Video streaming – RealPlayer, Windows Media Player Telephone – VoIP (voice over IP) Time Keeping – NTP And on, and on…- managed by IETF
Internet Applications We Take For Granted Domain Name Service – DNS E.g. minerva.albany.edu -> 169.226.1.120 Network management – Ping, TraceRT, SNMP (Simple Network Management) Time Keeping – NTP And on, and on…- managed by IETF
Myth: Internet = Web NOT!!! Proof? Nothing up to this point has to to do with the Web Everything up to this point has to do with the Internet Applications up to this point do not HAVE to be done via the web, for example: Gopher WAIS Windows client/server programs – e.g. Eudora email However, most applications use web standards and protocols are due to the economies of standard software already developed Web Technology World Wide Web Developed by Tim Berners-Lee in early 1990s Client/server set of Internet applications Linking documents from diverse sources requires A defined system for linking the documents Protocols that allow different computers to communicate Tools to assist in creating the documents and the links between them Web Technology (Continued) Hypertext Transfer Protocol (HTTP) Used to control communication between Web clients and servers Web browser Used to request Web pages from Web servers Web server Stores and delivers Web pages and other Web services URL Indicates where a particular Web page resides on the Internet
Web Markup Languages Hypertext Markup Language (HTML) Used to specify the formatting of a Web page HTML tag Command that tells a Web browser how to display items on a page XML A markup language for de-signing data classification Web Markup Languages (Continued) XML Web content Implemented using several files Another that provides the actual data A third that defines the format of the presentation of the data in a Web browser
Cookies Small text files stored on, and retrieved from, your computer Used to Store information about who you are and what your interests are Privacy advocates Criticize cookies as gathering too much information about visitors Web browsers Allow you to disable cookies Search Engines, Subject Directories, and Portals Information overload The inability to find the information you need due to an overabundance of unrelated information Search engine Tool for finding information on the Web Meta search engine Allows you to run keyword searches on several search engines at once Search Engines, Subject Directories, and Portals (Continued) Subject directory Sites collected and organized by human beings Web portals Web pages that serve as entry points to the Web
Classified under one of the following categories Communication and collaboration News Education and training E-commerce Travel Banking, finance, and investing Web Applications (Continued) Communication and Collaboration Web is used as communication link for homes and offices News Allows public to research issues Webcasting takes advantage of streaming video technology and highspeed Internet connections City newspapers and major news agencies are accessible over the Web Education and Training Educational institutions of all types and sizes Use the Web to enhance classroom education Educational support products (Blackboard and WebCT) Provide an integrated Web environment Distance education Conducting classes over the Web with no physical class meetings Travel The Web Has had a profound affect on the way we plan and prepare for trips Mapquest Assists travelers in finding their way around town and between towns Travel Web sites Assist travelers in finding the best deals on flights, hotels, car rentals, vacation packages, and cruises
Employment and Careers Select a career Discover who the players are in your chosen career Learn about the companies that interest you Network with others in the field View job listings at general employment Web sites Multimedia and Entertainment Internet radio Digitally delivered to your computer over the Internet Streamed music You can select songs and create your own play lists Tethered downloads Actual music files are downloaded to your computer Portable downloads Transfer the music files to your computer Multimedia and Entertainment (Continued) Movie industry Also making the move to Internet distribution Games Multiplayer games support Genre of multiplayer online games Action Board Card Flight Simulation
Research on the Web Curiosity research Looking up information at the moment a thought or question strikes us Responsible for most of the world’s great inventions Assigned research Selecting and Refining a Topic Generally done through many stages of refinement
Sources of Information Library and online databases Primary source of deep, trustworthy, authoritative information Libraries Resources are professionally analyzed and categorized Knowledgeable researchers/librarians are available to assist with your project
Sources of Information (Continued) Online research databases Visitors can search for information in journals, magazines, and newspaper articles Information database services Offer the best in quality and convenience LexisNexis Academic Universe One of the most popular private databases Citing Sources Plagiarism Representing someone else’s writing as your own Copyrighted material (intellectual property) Protected by law Cannot be copied and presented as your own work Citation How you formally recognize the source of a quotation What’s New in Internet and Web Technology? Internet phone Internet phone companies provide all the same services as standard phone companies, but the advantages include low monthly fees, no added cost for extra phone services, and little or no federal taxes. Blogs and instant messaging go to work Blog is short for Web log, and is a type of Web bulletin board facility that allows participants to post messages. Businesses are using blogs for enhanced company communication. What’s New in Internet and Web Technology? E-voting E-voting is met with concerns of hacking, compromised privacy, and vote alteration. What’s New in Internet and Web Technology? The Mystery of Nigritude Ultramarine and A9 Summary Internet Largest publicly owned network of networks Types of Internet-based communications Synchronous or asynchronous Text-based, voice-based, or video-based Forms of text communications include E-mail Discussion boards Instant messaging Summary (Continued) The Web Makes use of the Internet’s client/server technology Uses Hypertext Transfer Protocol (HTTP) Provides communication and collaboration platforms One of the first places people turn to when looking for employment
|
|
Bosh sahifa
Aloqalar
Bosh sahifa
Describe how hardware, protocols, and software work together to create the Internet Compare and contrast the types of communication tools available on the Internet
|
