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Chapter 3

Chapter 3. Fluency with Information Technology 4 th edition by Lawrence Snyder (slides by Deborah Woodall : woodall@mc.edu). Network Defined. computer network Two or more computer systems that can communicate with each other over some communications media.

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Chapter 3

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  1. Chapter 3 Fluency with Information Technology 4th edition by Lawrence Snyder (slides by Deborah Woodall : woodall@mc.edu)

  2. Network Defined computer network Two or more computer systems that can communicate with each other over some communications media. communications mediamay be classified as wired - telephone lines, coax, fiber optic wireless - microwave, satellite

  3. Far and Near • LAN – Local Area Network • WAN – Wide Area Network • The Internet – A global network of Wide Area Networks

  4. Classifying Communication Communication can be classified as either… • asynchronous – sending and receiving occur at separate times • synchronous – sending and receiving occur at the same time

  5. Classifying Communication Also Communication can be classified as either… • broadcast – one sender, many receivers • multicast – one sender, many selected receivers • point-to-point – one sender, one receiver

  6. Communication Classifications • In one way or another the Internet offers all of these forms of communication. • The Internet is truly a universal communications medium.

  7. The Client/Server Structure • Most encounters on the Internet reflect the client/server structure. • client: (e.g. your browser) requests a service (like a Web page) • server: (e.g. Web Server) provides a service (like sending a Web page)

  8. The Client/Server Structure • A client and a server have one or more BRIEF relationships. • An advantage: The server can handle many clients in a short period of time.

  9. IP Addresses • Every transmitted message on the Internet requires a destination address • IP address – the address of a computer connected to the Internet

  10. IP Addresses • Each IP address is a series of 4 numbers separated by dots, e.g. 234. 18. 45. 1 • Each of the 4 numbers takes up one byte of memory, so an IP address is a 4 byte address.

  11. IP Addresses The IP address from the previous slide would look like this when stored in RAM 234. 18. 45. 1 11101010 00010010 00101101 00000001

  12. IP Addresses • How many numbers will fit into one byte?

  13. IP Addresses • What would be the range of one of the numbers in an IP address?

  14. IP Addresses Why is each of the following an invalid IP address? 34.678.32.90 -89.53.244.32 34.23.67.89.145

  15. IP Addresses • And finally, how many IP addresses are possible using the current scheme? 232 >4.3 billion • There is an upgrade being planned for IPv4 called IPv6 – a 16 byte IP addressing scheme - e.g. 69DC:77AC:FF66:A1A2:BCDF:77AC:FF66:3459

  16. IP Addresses • Your PC has an IP address when connected to the Internet • temporary if connected by modem • permanent (or temporary) if connected to a LAN • Computers deal with numbers but humans don’t do very well remembering numbers.

  17. Domain Names • A domain is a related group of networked computers. • A domain name is a symbolic name for a 4-byte IP address, and thus a particular computer on the Internet.

  18. Domain Names • An example: www.mc.edu www is a specific computer in the mc domain of the edudomain • A domain name reveals a hierarchy.

  19. Domain Names

  20. Domain Names • Original top-level domains • .edu • .org • .net • .mil • .gov • .com • Newer top-level domains • .biz (businesses) • .info (information) • .museum (museums) • .name (individuals) • .pro (credentialed professionals) • country codes

  21. Domain Names The purpose of a top level domain name is to indicate • Function, or • Location

  22. The Domain Name System • We like www.jvim.com • Computers like 198.160.140.235 • Where does your browser get the IP Address for a domain name? DNS Servers

  23. TCP/IP • Once the address of the computer is found, how is the message actually sent over the Internet? TCP/IP • TCP/IP protocol specifies that the message is broken into pieces and each piece goes into a packet.

  24. TCP/IP • Each packet contains • A piece of the message being sent • The destination address for the packet • The source address of the packet • A collating number • Each packet is independent.

  25. Ethernet • How is a message sent over a LAN? Ethernet Protocol • Ethernet also uses packets. • Ethernet is a true broadcast medium.

  26. Connecting to the Internet How are computers connected to the Internet? • Connect to an Internet Service Provider (ISP) e.g. bellsouth.net, comcast.com, earthlink.net • 56K dial-up modem • DSL • Cable modem • Satellite • Cell phone • Connect through a campus or enterprise network.

  27. The World Wide Web • The WWW is not the same as the Internet. • The WWW is a subset of the Internet. • The WWW is made up of Web servers and their files (Web pages and associated files). • Web pages are NOT stored as bytes of pixel data but as a description of the page. • The WWW is organized hierarchically.

  28. http://www.mc.edu/campus/clubs/acm/members.html http:// • stands for Hypertext Transfer Protocol • tells the computer how to handle the file • indicates this is a Web page

  29. http://www.mc.edu/campus/clubs/acm/members.html www.mc.edu • the domain name • represents the IP address of the server (a computer) • specifies a hierarchy from specific to general (www is a computer in the mc domain of the edu domain) • not case sensitive

  30. http://www.mc.edu/campus/clubs/acm/members.html campus/clubs/acm/members.html • the path name telling which page and where it is on the server • specifies a hierarchy from general to specific (in the campus folder is a clubs folder containing an acm folder containing a Web page file called members.html) • may be case sensitive

  31. Wrap Up • mc.edu vs. www.mc.edu • http://www.mc.edu/faculty/woodall

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