Ch. 3 FIT5, CIS 110 13F

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Ch. 3 FIT5, CIS 110 13F

  1. 1. Chapter 3 The Basics of Networking Friday, October 18, 13
  2. 2. General Communication • Synchronous communication: – (eg) wired telephone network => circuit-switched network • Asynchronous communication: – (eg) email; the internet => packet-switched network Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  3. 3. Internet’s Communication Properties • point-to-point, asynchronous communication • fast enough to mimic synchronous communication (e.g., VOIP) • Multicasting is possible (chat rooms, radio, tv) Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  4. 4. Internet Schematic Diagram Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  5. 5. Client/Server Structure • Most Internet applications are client/server interaction – click a hyperlink: your computer connects to server – page returned => connection ends – Next connection is brand new => Stateless protocol No memory of prior connection Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  6. 6. Basic Client/Server Interaction Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  7. 7. Many Brief Relationships • server can handle many clients at a time • server is busy only for as long as it takes to perform your request • Google: 5,134,000,000 searches/day (2012) Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  8. 8. Client/Server Relationships Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  9. 9. Internet Protocol (IP) Address • Each computer on the Internet has a unique IP address – four numbers separated by dots: 128.223.223.85 => “dotted quad” – each number is 0–255 (one byte / 8bits each) => “octet” Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  10. 10. IP Addresses Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  11. 11. IPv4 Address Exhaustion – each of the four numbers is • in the range 0–255 • requires one byte (8 bits) of memory => “octet” – IP address is 4x8= 32 bits long => IP addresses in short supply. Why? 2^32 = 4.3 billion, a finite number (ask Google the exact value) Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  12. 12. IPv6: 128 bit addresses – IPv6 addresses will have 16, 8-bit, fields 2^128 = 10^38 – 10^28 times as many addresses as IPv4 – new switching hardware/software is required to handle IPv6 Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  13. 13. Domain Names – symbolic names (human-readable) vs. IP addresses – based on hierarchy of domains – domain: related group of networked computers – (eg) pages.uoregon.edu Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  14. 14. Domain Names • Domain name hiearchy reads right-to-left ix.cs.uoregon.edu – top-level domain: edu – subdomain uoregon – next subdomain cs – server is ix Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  15. 15. The .edu Domain Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  16. 16. DNS Servers • Domain Name System (DNS): translates domain names into IP address • Every Internet host knows the IP address of its nearest DNS name server • How the DNS Works (youtube, 00:02:25) http://bit.ly/ab4s50 Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  17. 17. DNS Servers • your computer asks a DNS name server to translate a name to an IP address • If the address is not stored on the DNS name server), the server asks an authoritative name server • 13 root name servers keep the complete list of all authoritative name servers Tagged A..M here: www.root-servers.org Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  18. 18. DNS Root Servers • 13 root name servers (A..M) scattered around the world • Plus 243 mirror sites => DNS is the world’s largest distributed database Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  19. 19. TCP/IP • TCP/IP Postcard Analogy – The Internet is like sending a novel to your publisher using postcards – Packet Switching Flash Demo – Packet Layer in OSI Network Model Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  20. 20. TCP/IP • packets routed around failed nodes – ensures delivery of entire message – large scale, built-in redundancy – crucial to reliability • packet switching => rapid store-&-forward design • node receives a packet, stores it • determines best route to destination • sends it to next node Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  21. 21. TCP/IP: The Language of the Internet – analogy: “postcards” = IP packets – travel different routes / arrive out of order – can be lost IP: stamps packet w/address & packet number TCP: re-arranges, requests retransmission – network can optimize packet paths, but.. – prone to chaos Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  22. 22. Ethernet • Ethernet uses a physical channel – wire, cable, or optical fiber – media layer / physical layer • Key point: Each packet seen by all computers on the local network => store-&-forward design Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  23. 23. Ethernet Analogy Party Protocol • How an Ethernet network works: – two people start speaking at same time => collision • Collision Resolution policy – wait random amt of time – try again Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  24. 24. Ethernet Analogy • How an Ethernet network works: – Party Protocol – two people start speaking at same time => collision • Collision Resolution – wait random amt of time – try again Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  25. 25. Figure 3.9. Media Layer Robert Metalfe’s original drawing of the Ethernet-computers “tap” onto the wire labeled “The Ether” Slide 3Friday, October 18, 13
  26. 26. The World Wide Web (http) • client/server protocol • requests: URL (a.k.a. URI) • client & server both “speak” HTTP Jeopardy Category: Application Layer Q: The World Wide Web A: What is, an Internet Application? Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  27. 27. File Systems: How to Organize your Folders • Folders on the server are called Directories • Directory Hierarchy – folders can contain folders as well as files => the file system, or directory hierarchy • Think of any hierarchy as a tree – folders are branches – files are the leaves – root directory is at the top of the hierachy Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  28. 28. Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  29. 29. File System Pathnames • Files are identified by the path from the root diretory to the file: – (eg) /fluency/part1/chapter3/file-structure/ directory-hierarchy/figure-3-13.pdf • Note: do not use spaces or special characters in a Unix pathname Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  30. 30. Pathnames & URIs • Part of a web page file’s pathname is used in the URI: URL: pages.uoregon.edu/susanq/110/ Unix pathname on server: /home7/susanq/public_html/110/ URL: pages.uoregon.edu/susanq/110/p2/index.html Unix pathname on server: /home7/susanq/public_html/110/p2/index.html Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  31. 31. Web Directories: The Default Document • When a URL ends in a slash: => browser automatically looks in that folder for a file called index.html or default.html => default document => supresses directory listing in browser Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  32. 32. Organize your Folders • Why have a hierarchy? – organize your thinking & work – directories/folders cost nothing – work on the server and your computer => highly recommended Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13
  33. 33. Ch. 3: Assessment Learning Outcomes - Know the following Copyright © 2013 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Friday, October 18, 13

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