COS 125 Day 3 & 4

Agenda Questions from last Class?? Today’s topics Connecting to the Internet Assignment #1 due next class Quiz #1 on Feb 3, two weeks from today Change to syllabus New Syllabus posted in WebCT Chap 1-28

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

Where do you get Internet Service ISP St. John Valley Communications Pivot. net Eathlink Bluelight Online Service AOL MSN

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)

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

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

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

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

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

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

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

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

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 The internet allows Interactive use Greater bandwidth means TV like performance Existing TV cable system also can bring you High Speed Internet service TV and Internet are combined in some services like MSN TVMSN TV MSN bought out Web TV

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

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

Internet Enhanced TV TV networks send both TV signal and digital information to your homes A special receiver formats digital signals and overlays that information on the TV image Digital information is interactive WWW HTML

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 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

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

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

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

Old Online services Available prior to public internet service (ISPs ~ 1995) BBS (bulletin board service) AOL, Prodigy, CompuServe Some local BBS’s Gave you & 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

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

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

WiFi standards b 2.4 GHz GHz GHz Devices must have a WiFi card and they connect to Wireless Access Points (Hot spots)

WiFi

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

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

Wardriving

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 pint 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

Chalk Symbols

Satellite Internet

Orbits

GEO Satellite System 2. Point-to-Point Uplink 3. Broadcast Downlink 4. Footprint 5. Earth Station A Earth Station B 1. Geosynchronous Satellite 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

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

WAP

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

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

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

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

versus Bluetooth LANs Scalability Cost Battery Drain Bluetooth Good through having multiple access points Poor (but may get access points) Probably higherProbably Lower HigherLower DiscoveryNoYes Discovery allows devices to figure out how to work together automatically

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

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

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

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

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

WiFi Home network

Smart House If your home has a network then can get Internet enabled appliance Control systems that you can access from anywhere Security systems Places to check