1.  If not your UW e-mail address, be sure to include your name (or even your UW netID) in the message  Sign your e-mails with your name (and preferably in English)  Also e-mail your TA to ensure we reply promptly 2012-04-02Katherine Deibel, Fluency in Information Technology1

2.  Now posted on the website  You can attend any TA’s office hours  My hours are  after class on Fridays  by appointment  when I’m in my office with the door open 2012-04-02Katherine Deibel, Fluency in Information Technology2

3. Fluency with Information Technology 2012-04-02Katherine Deibel, Fluency in Information Technology 3 Katherine Deibel INFO100 and CSE100 Katherine Deibel

4.  Computers are useful alone, but are better when connected (networked)  Access more information and software than is stored locally  Help users to communicate, exchange information…changing ideas about social interaction  Perform other services—printing, Web, email, texting, mobile, etc. 2012-04-02Katherine Deibel, Fluency in Information Technology4

5.  Different networks depending on distance between computers:  Local area network (LAN) ▪ Small area: room or building ▪ Either wired or wireless  Wide area networks (WAN) ▪ Large area: more than 1 km ▪ Fiber-optic, copper transmission lines, satellite 2012-04-02Katherine Deibel, Fluency in Information Technology5

6. 2012-04-02Katherine Deibel, Fluency in Information Technology6 Network TypeDifferentiating Factors Peer-to-Peer No computer running server software Server-Based NetworksComputer running server software manages network traffic Local Area Network (LAN)Limited geographical area Wide Area Network (WAN)Across town or across the globe Third-party service provider More bandwidth = more expense Connects to LANs with a router Campus NetworkBuildings in close proximity Metropolitan Area Network (MAN) Clusters of buildings in close proximity separated from other clusters Third-party service provider

7.  To communicate computers need to know how to set up the data to be sent and interpret the data received  Example protocols  EtherNet—for physical connection in a LAN  TCP/IP: transmission control protocol / internet protocol (Internet)  HTTP: hypertext transfer protocol (Web) 2012-04-02Katherine Deibel, Fluency in Information Technology7

8.  EtherNet is a popular LAN protocol ▪ Recall, it’s a “party” protocol 2012-04-02Katherine Deibel, Fluency in Information Technology8 Connection to campus network infrastructure PC Ether Net Cable Typical MGH or OUGL Lab

9.  The campus subnetworks interconnect computers of the UW domain which connects to Internet via a gateway 2012-04-02Katherine Deibel, Fluency in Information Technology9 All communication by TCP/IP Homer Dante Student CS MGH Gateway washington.edu Internet

10.  Transfer Control Protocol / Internet Protocol  The primary protocol for data transmission on the Internet  Video: Warriors of the Net  http://www.youtube.com/watch?v=PBWhzz_Gn10 http://www.youtube.com/watch?v=PBWhzz_Gn10  Linked to on the Calendar page 2012-04-02Katherine Deibel, Fluency in Information Technology10

11.  Again, a video: History of the Internet http://vimeo.com/2696386 http://vimeo.com/2696386  The basic story:  Computer systems at multiple locations  Desire to share data and eliminate duplicate work  Two major design challenges 2012-04-02Katherine Deibel, Fluency in Information Technology11

12.  Diversity of systems in place 2012-04-02Katherine Deibel, Fluency in Information Technology12 Site C: Uses carrier pigeons Site B: Morse Code Site A: Pig Latin Not feasible to rebuild every site with the same type of connectivity

13.  Diversity of systems in place Solution: Accept the diversity 2012-04-02Katherine Deibel, Fluency in Information Technology13 Site C: Uses carrier pigeons Site B: Morse Code Site A: Pig Latin

14.  Within a local network, any protocol is allowed  To send messages outside a local network, it must be converted into the IP protocol 2012-04-02Katherine Deibel, Fluency in Information Technology14

15. 2012-04-02Katherine Deibel, Fluency in Information Technology15 A Pig Latin Network A convert Pig Latin into IP Packets and sends out on Internet IP B Network B converts IP into Morse Code Morse Code IP

16. 2012-04-02Katherine Deibel, Fluency in Information Technology16 Turtle Cobra Crocodile Squirrel Echidna Mole Reptiles Mammals DNA

17. 2012-04-02Katherine Deibel, Fluency in Information Technology17 AOL Comcast ClearWire UW UBC UM ISPs University Networks IP connects them all

18. 2012-04-02Katherine Deibel, Fluency in Information Technology18 ? ? ? ? ? ? ? ? ? Talk with your neighbor for a minute and come up with other examples of hourglass analogies.

19.  Diversity of systems in place  Maintain communication in times of disasters, breakdowns, etc. 2012-04-02Katherine Deibel, Fluency in Information Technology19

20.  Diversity of systems in place  Maintain communication in times of disasters, breakdowns, etc. Solution: Postcard analogy 2012-04-02Katherine Deibel, Fluency in Information Technology20

21.  Break messages into parts  Send each message separately  Delivery:  Each card moves forward to a server that knows how to get to the destination  Cards can take multiple paths  Cards arrive out of order 2012-04-02Katherine Deibel, Fluency in Information Technology21

22. 2012-04-02Katherine Deibel, Fluency in Information Technology22 You can find such “trace route” sites through Google tracert 128.227.205.2

23.  People give computers domain names  Hierarchical scheme  Domains begin with a “dot” and get “larger” going right ▪.edu All educational computers, a TLD ▪.washington.edu All computers at UW ▪ dante.washington.edu A UW computer ▪.ischool.washington.edu iSchool computers ▪.cs.washington.edu CSE computers ▪ june.cs.washington.edu A CSE computer 2012-04-02Katherine Deibel, Fluency in Information Technology23

24.  Computers are named by IP address, four numbers in the range 0-255 ▪ cse.washington.edu: 128.95.1.4 ▪ ischool.washington.edu: 128.208.100.150  Remembering IP addresses would be brutal for humans, so we use domains  Computers find the IP address for a domain name from the Domain Name System—an IP address-book computer 2012-04-02Katherine Deibel, Fluency in Information Technology24

25. .edu.com.mil.gov.org.net domains are “top level domains” for the US  Recently, new TLD names added  Each country has a top level domain name: ▪.ca (Canada) ▪.es (Spain) ▪.de (Germany) ▪.au (Australia) ▪.at (Austria) ▪.us (US) 2012-04-02Katherine Deibel, Fluency in Information Technology25

26.  View the Internet in two ways:  Humans see a hierarchy of domains relating computers—logical network  Computers see groups of four number IP addresses—physical network  Both are ideal for the “user's” needs  The Domain Name System (DNS) relates the logical network to the physical network by translating domains to IP addresses 2012-04-02Katherine Deibel, Fluency in Information Technology26

27.  Many people misuse the terms “Internet” and “World Wide Web”  Let’s get them right 2012-04-02Katherine Deibel, Fluency in Information Technology27 Internet: All of the wires, fibers, switches, routers etc. connecting named computers Internet: All of the wires, fibers, switches, routers etc. connecting named computers World Wide Web: That part of the Internet that stores and serves Web pages—web servers, client computers World Wide Web: That part of the Internet that stores and serves Web pages—web servers, client computers

28.  The terms "internet" and "Internet" refer to different things  "Internet" is the complete collection of internetworked computers  "internet" refers to any collection of networked computers  Most of the time, you probably mean the "Internet" 2012-04-02Katherine Deibel, Fluency in Information Technology28

29.  Networking is changing the world  Internet: named computers using TCP/IP  WWW: servers providing Web pages  Principles ▪ Logical network of domain names ▪ Physical network of IP addresses ▪ Protocols rule: LAN, TCP/IP, http... ▪ Domain Name System connects the two ▪ Client/Server, fleeting relationship on WWW 2012-04-02Katherine Deibel, Fluency in Information Technology29

30.  Net neutrality  SOPA  Digital divide  Government control of Internet access  Web 2.0  VPNs  Wireless pirating  Etc. 2012-04-02Katherine Deibel, Fluency in Information Technology30 These topics could be interesting fodder for GoPost discussions

31.  Check the calendar for due dates  Read Chapters 5 & 6  Continue GoPosting 2012-04-02Katherine Deibel, Fluency in Information Technology31