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The Internet

The Internet. COSC-100 (Elements of Computer Science) Prof. Juola. Basic Concepts. Networks -- computers communicating with each other Enables sharing of hardware, software, and data

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The Internet

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  1. The Internet COSC-100 (Elements of Computer Science) Prof. Juola

  2. Basic Concepts • Networks -- computers communicating with each other • Enables sharing of hardware, software, and data • Network card (peripheral) connects to other computers, possibly through series of intermediaries (routers, etc.)

  3. Technical issues • Binary data (1/0) encoded as sound for “modem” • Alternatively, use cable modem, DSL, wireless, etc. • Several problems • Many computers, one peripheral • Many programs, one computer • What do ones and zeros mean, anyway

  4. Finding the target • Most computers are hooked to “routers” • Routers are like telephone switches and direct the bits around. • Computers have several “addresses • Mine : • MAC address • IP address (165.190.169.24) • Name (shannon.mathcomp.duq.edu)

  5. Finding programs • Data is delivered to computers in “packets”, addressed by IP address and “port” • “Port” controls what program actually gets the data. • Examples • SSH is port 22 • Mail is port 25 • Web is port 80

  6. Protocols • Meaning established by protocols; each side of the conversation has a script Knock Knock Who’s there? Theseus Theseus who? Theseus a simple example of a protocol

  7. Client/Server Computing • Server provides “service” to the universe at large (e.g. http server, mail server) • “Client” programs can connect and request service. • Sample clients • Web browsers (IE, Netscape, Mozilla) • Mail clients (Eudora, Pine) • Games (MMORPGs, Quake, Doom)

  8. Sample protocol (http) • Hyper Text Transfer Protocol • Client program reads address bar • Looks up machine name • Requests file from server machine • May re-request if data times out or if other data (e.g. animations, pictures) needed

  9. Networking advantages • Shared resources. One db, many users • Convenient communications • Less intrusive than telephone • Allows time-shifting • Better access (see on-line libraries)

  10. Problems • Reliability • Security • Privacy • Humanity

  11. Email Problems • Machine failures • Overwhelming • Unsolicited (spam) • Privacy threat • Forgery • Can be (often is) ignored • Dehumanizing

  12. Protecting yourself • Protect your privacy (identity theft, password theft) • Cross-check what you see on-line • Limit time on-line • Avoid information overload • Most importantly, be aware

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