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COS 125

COS 125. Day 3. Agenda. Questions from last Class?? Today’s topics Connecting to the Internet Assignment #1 is due on Feb 5 Quiz #1 on Feb 12 Chap 1-26 20 M/C, 4 short essays, One extra credit Question 60 Min, open book, open notes. Connecting to the Internet.

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COS 125

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  1. COS 125 Day 3

  2. Agenda • Questions from last Class?? • Today’s topics • Connecting to the Internet • Assignment #1 is due on Feb 5 • Quiz #1 on Feb 12 • Chap 1-26 • 20 M/C, 4 short essays, One extra credit Question • 60 Min, open book, open notes

  3. Connecting to the Internet • Lots of ways to connect with more being invented • General rule >>> faster is better • In order of speed • Telephone modem • Cable modem or DSL • Direct LAN connection • Newest way is wireless • WiFi, Cellular, WiMAX

  4. Where do you get Internet Service • ISPs • St. John Valley Communications • Pivot.net • EarthLink • Bluelight • Online Service • AOL • MSN

  5. How a modem works • Modems allow digital signals to go over an analog circuit • Analog Data • Smooth changes among an infinite number of states—like hands going around an analog clock • Digital Data • Few states • In a digital clock, each position can be in one of ten states (the digits 0 through 9)

  6. Quiz • Which is Analog? Which is Digital? On/Off Switch Number Of Fingers Clock Calendar TV Audio CD

  7. Sending data with a modem Modulated Analog Signal Telephone Binary Data 1010010101 PSTN Modem Computer Amplitude (Loudness or Intensity) Modulation 1 0 1 1 1011 becomes loud-soft-loud-loud

  8. Getting Data with a modem Modulated Analog Signal Demodulated Binary Data Telephone 1010010101 PSTN Modem Computer Amplitude (Loudness or Intensity) Modulation 1 0 1 1 Loud-soft-loud-loud becomes 1011

  9. Modems • Two types • Internal • External • Computers control modems using the Hayes Command Set • In the early days of the Internet (early 1990’s) users had to program the modems using Hayes command set to connect to an ISP

  10. Modem Speeds • V.34 • Send and receive at up to 33.6 kbps • Fall back in speed if line conditions are not optimal • V.90 • Receive at up to 56 kbps • Send at up to 33.6 kbps • Asymmetric speed is good for WWW service. • Other party must have a digital connection to the PSTN

  11. Modem Speeds • V.92 • Receive at up to 56 kbps • Send at up to 33.6 kbps or higher if the line permits • Other party must have a digital connection to the PSTN • Modem on hold: can receive an incoming call for a short time without losing the connection • Cuts call setup time in half

  12. Telephone Modem Communication Need Modem at Each End Up to 33.6 kbps Analog Modulated Signal Binary Data Modem Telephone 33.6 kbps Modem Telephone Server A Client A PSTN

  13. Figure 7.2: Telephone Modem Communication PSTN Digital Access Line Server B 56 kbps Modem Telephone Client B For 56 kbps Download Speed Server Must Have a Digital Connection (ISDN PRI), Not a Modem

  14. How Internet TV works • TV was the first “Information Super highway” • Able to move of lot of info to the user • Problem was User could not interact with the info • Unidirectional • The internet allows Interactive use • Greater bandwidth means TV like performance http://wwitv.com/ • Existing TV cable system also can bring you High Speed Internet service • TV and Internet are combined in some services like MSN TV • MSN bought out Web TV

  15. Cable Modem Services ISP 2. Optical Fiber to Neighborhood 4. Coaxial Cable to Premises 3. Neighborhood Splitter 1. Cable Television Head End 5. Cable Modem Subscriber Premises PC 6. Requires NIC or USB port

  16. MSN TV • Can watch TV and get on the Internet at the same time • Requires • MSN TV receiver (keyboard & mouse) • Phone access • TV • Receiver acts like a PC and TV receiver all at once • Uses a proprietary web browser and lots of proxy web servers

  17. Internet Enhanced TV • TV networks send both TV signal and digital information to your homes • http://en.wikipedia.org/wiki/Interactive_television • A special receiver formats digital signals and overlays that information on the TV image • Digital information is interactive WWW HTML

  18. Digital Subscriber Lines • Uses existing Phone lines to get very high speed Internet Access • Up to 55 Mbps (1000 times faster than a V.90 modem) • Normal speeds for ADSL is 384 kbps down/ 96 kbps up • Pivot.net 768 kbps down/128 kbps up • On 24/7 and doesn’t interfere with regular phone usage • The faster the DSL speed the closer you must be to the phone company

  19. ASDL with Splitter Subscriber Premises Telephone Company End Office Switch Data WAN 1. Existing Single Pair of Voice-Grade UTP Wires ADSL Modem PC DSLAM Splitter 3. PSTN 2. Telephone

  20. ASDL with Splitter 1. Data 256 kbps to 1.5 Mbps Subscriber Premises Telephone Company End Office Switch Data WAN 2. 64 kbps to 256 kbps ADSL Modem PC DSLAM Splitter PSTN Telephone

  21. ASDL with Splitter Subscriber Premises Telephone Company End Office Switch Data WAN ADSL Modem PC DSLAM Splitter PSTN 1. Ordinary Telephone Service Telephone

  22. How DSL works • ADSL • UP < Down • Uses POTS • Distance effects Bandwidth • Phone service is normal

  23. Old Online services • Available prior to public internet service (ISPs ~ 1995) • BBS (bulletin board service) • AOL, Prodigy, CompuServe • Some local BBS’s • Gave you email & chat only with other users of the same online service • Allowed file transfers up and down • Applications, pictures, music • Required subscription fees and phone access • Never really popular in rural areas

  24. Modern Online Services • Internet Plus • Gives access to all (or most) of the Internet through gateways • Several Propriety applications • Lost of data “firewalled” away from the Internet • “Walled gardens” • Most common is AOL and MSN • Both use TCP/IP • Great for Internet Novices • Much greater control over Spam, viruses

  25. How Wireless works • All sorts of devices • Laptops • PDA • Cell phones • Peripherals • Many types of wireless • WiFi • Satellite • Bluetooth • Cellular • WiMAX

  26. WiFi • 802.11 standards • 802.11b • 11Mbps @ 2.4 GHz • 802.11a • 54 Mbps @ 5 GHz • 802.11g • 54 Mbps @ 2.4 GHz • Devices must have a WiFi card and they connect to Wireless Access Points (Hot spots)

  27. WiFi

  28. Typical 802.11 Wireless LAN Operation with Access Points Access Point Industry Standard Coffee Cup Wireless Notebook NIC Antenna (Fan) To Ethernet Switch PC Card Connector

  29. Typical 802.11 Wireless LAN Operation with Access Points CSMA/CA+ACK Switch UTP Radio Link Access Point A Notebook UTP Handoff If mobile computer moves to another access point, it switches service to that access point Access Point B Client PC Server Large Wired LAN

  30. Wardriving

  31. War Drive How To • Equipment needed • Car • Another person (prevents accidents!) • Laptop with wireless access • Wireless antenna optional • Netstumbler software • GPS unit • Drive around till Netstumbler detects an access point • Analyze access point • Record coordinates using GPS • Mark on Electronic Map • Chalk mark sidewalk • Why? • Most access points are not secure (no WEP) • Allows free internet access • Hackers use as entry points to get to other more secure networks

  32. Chalk Symbols

  33. WiMAX • 802.16 standard • Uses cell towers • Home or pc based http://computer.howstuffworks.com/wimax1.htm

  34. Satellite Internet

  35. Orbits

  36. GEO Satellite System 1. Geosynchronous Satellite 2. Point-to-Point Uplink 3. Broadcast Downlink 4. Footprint 5. Earth Station A Earth Station B Satellite appears stationary in sky (35,785 km or 22,236 mi) Far, so earth station needs dish antenna At speed of light takes 250 ms to travel distance

  37. Wireless Internet Access for small devices • Cell phones and PDA do not have big enough screens for full size Web Pages • WAP • Wireless access protocol • WML • Wireless markup language • WAP gateways converts regular HTML to WML and vice versa

  38. WAP

  39. BlueTooth • Wireless networks for peripherals • Personal Area Network • Does not provide Internet Access • Limited range

  40. Personal Area Networks (PANs) • Connect Devices On or Near a Single User’s Desk • PC, Printer, PDA, Notebook Computer, Cellphone • Connect Devices On or Near a Single User’s Body • Notebook Computer, Printer, PDA, Cellphone • The Goal is Cable Elimination

  41. Personal Area Networks (PANs) • There May be Multiple PANs in an Area • May overlap • Also called piconets

  42. 802.11 versus Bluetooth LANs 802.11 Bluetooth Focus Large WLANs Personal Area Network Speed 11 Mbps to 54 Mbps In both directions 722 kbps with back channel of 56 kbps. May increase. Distance 100 meters for 802.11b (but shorter in reality) 10 meters (may increase) Number of Devices Only 10 piconets, each with 8 devices maximum Limited in practice only by bandwidth and traffic

  43. 802.11 versus Bluetooth LANs 802.11 Bluetooth Scalability Good through having multiple access points Poor (but may get access points) Cost Probably higher Probably Lower Battery Drain Higher Lower Discovery No Yes Discovery allows devices to figure out how to work together automatically

  44. Figure 5.11: Bluetooth Operation Notebook Master File Synchronization Client PC Slave Printing Printer Slave Piconet 1 Cellphone Telephone

  45. Figure 5.11: Bluetooth Operation Notebook Client PC Printing Printer Slave Call Through Company Phone System Cellphone Master Telephone Slave Piconet 2

  46. Figure 5.11: Bluetooth Operation Notebook Master File Synchronization Client PC Slave Printing Printer Slave Piconet 1 Call Through Company Phone System Cellphone Master Telephone Slave Piconet 2

  47. Home Networks • Many Homes have more than one computer or Internet Device • Don’t want to provide Internet to each device independently • Connect all device to a network and provide Internet access to the Home networks • Sometimes called SOHO networks • SOHO >> small office/home office

  48. Needed to build home Networks • Internet Access • Broadband DSL or Cable modem • A way to connect all devices • Wired with Ethernet • Hub or Switch • Expensive • Wireless (WiFi) • Easier & Cheaper • A network Address Scheme • Most broadband device provide DHCP • Use Microsoft Internet Connection Sharing • ME, XP, Windows NT • Firewall • Keep hackers out

  49. WiFi Home network

  50. Wireless Media • Get rid of wiring • PPP or Multi • http://www.dlink.com/products/?pid=318 • Wireless Speakers

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