COS 125 Day 3. Agenda Questions from last Class?? Todays topics Connecting to the Internet Assignment #1 is due on Feb 5 Quiz #1 on Feb 12 Chap 1-26 20.

COS 125

Day 3

Agenda

Questions from last Class??Today’s topics

Connecting to the InternetAssignment #1 is due on Feb 5Quiz #1 on Feb 12

Chap 1-2620 M/C, 4 short essays, One extra credit

Question60 Min, open book, open notes

Connecting to the Internet

Lots of ways to connect with more being inventedGeneral rule >>> faster is better

In order of speedTelephone modemCable modem or DSLDirect LAN connection

Newest way is wirelessWiFi, Cellular, WiMAX

Where do you get Internet Service

ISPsSt. John Valley CommunicationsPivot.net EarthLinkBluelight

Online ServiceAOLMSN

How a modem works

Modems allow digital signals to go over an analog circuitAnalog Data

Smooth changes among an infinite number of states—like hands going around an analog clock

Digital DataFew 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

NumberOf

Fingers

Audio CD

On/OffSwitch

TV

Sending data with a modem

Computer

Modem

Telephone

PSTN

Modulated AnalogSignal

1 0 1 1

Amplitude (Loudness or Intensity) Modulation

1010010101

Binary Data

1011 becomes loud-soft-loud-loud

Getting Data with a modem

Computer

Modem

Telephone

PSTN

Modulated AnalogSignal

1 0 1 1

Amplitude (Loudness or Intensity) Modulation

1010010101

DemodulatedBinary Data

Loud-soft-loud-loud becomes 1011

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

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

PSTNClient A

Server A Telephone

Telephone33.6kbps

Modem

Binary Data Analog ModulatedSignal

Modem

Need Modem at Each End Up to 33.6 kbps

Figure 7.2: Telephone Modem Communication

PSTN

Client B

ServerBTelephone

Digital Access Line

56 kbpsModem

For 56 kbps Download SpeedServer Must Have a Digital Connection (ISDN PRI), 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 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

Cable Modem Services

PCSubscriberPremises

5. CableModem

4. CoaxialCable toPremises

2. OpticalFiber to

Neighborhood

3.Neighborhood

Splitter

ISP

1. CableTelevisionHead 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 http://en.wikipedia.org/wiki/Interactive_television

A special receiver formats digital signals and overlays that information on the TV imageDigital 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 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

ASDL with Splitter

DataWAN

PSTN

DSLAM

ADSLModem

Splitter

Telephone

SubscriberPremises

Telephone CompanyEnd Office Switch

1.Existing

Single Pair ofVoice-GradeUTP Wires

PC

2. 3.

ASDL with Splitter

DataWAN

PSTN

DSLAM

ADSLModem

Splitter

Telephone

SubscriberPremises

Telephone CompanyEnd Office Switch

PC

1.Data

256 kbps to1.5 Mbps

2.64 kbps to256 kbps

ASDL with Splitter

DataWAN

PSTN

DSLAM

ADSLModem

Splitter

Telephone

SubscriberPremises

Telephone CompanyEnd Office Switch

PC

1.Ordinary Telephone

Service

How DSL works

ADSLUP < DownUses POTSDistance effects

Bandwidth Phone service is

normal

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

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 WiMAX

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)

WiFi

Typical 802.11 Wireless LAN Operation with Access Points

WirelessNotebook

NIC

Access Point

IndustryStandard

CoffeeCup

To EthernetSwitch

Antenna(Fan) PC Card

Connector

Typical 802.11 Wireless LAN Operation with Access Points

Switch

Client PCServer

Large Wired LAN

AccessPoint A

AccessPoint B

UTP Radio Link

HandoffIf mobile computermoves to another

access point,it switches serviceto 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 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

Chalk Symbols

WiMAX

802.16 standardUses cell towersHome or pc based

http://computer.howstuffworks.com/wimax1.htm

Satellite Internet

Orbits

GEO Satellite System

2. Point-to-PointUplink

3.BroadcastDownlink

4.Footprint5. 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 PagesWAP

Wireless access protocolWML

Wireless markup language

WAP gateways converts regular HTML to WML and vice versa

WAP

BlueTooth

Wireless networks for peripheralsPersonal Area NetworkDoes not provide Internet AccessLimited range

Personal Area Networks (PANs)

Connect Devices On or Near a Single User’s DeskPC, Printer, PDA, Notebook

Computer, CellphoneConnect Devices On or Near a

Single User’s BodyNotebook Computer, Printer,

PDA, CellphoneThe Goal is Cable Elimination

Personal Area Networks (PANs)

There May be Multiple PANs in an AreaMay overlapAlso called piconets

802.11 versus Bluetooth LANs

Focus

Speed

802.11 Bluetooth

Large WLANs Personal Area Network

11 Mbps to 54 MbpsIn both directions

722 kbps with backchannel of 56 kbps.

May increase.

Distance100 meters for 802.11b(but shorter in reality)

Numberof Devices

Limited in practice onlyby bandwidth and traffic

Only 10 piconets,each with

8 devices maximum

10 meters(may increase)

802.11 versus Bluetooth LANs

Scalability

Cost

Battery Drain

802.11 Bluetooth

Good through havingmultiple access points

Poor(but may get

access points)

Probably higher Probably Lower

Higher Lower

Discovery No Yes

Discovery allows devices to figure out how to work together automatically

Figure 5.11: Bluetooth Operation

File Synchronization

Client PCSlave

NotebookMaster

Printer SlavePrinting

Cellphone

Telephone

Piconet 1

Figure 5.11: Bluetooth Operation

Client PC

Notebook

Printer SlavePrinting

Call Through CompanyPhone System

CellphoneMaster

Telephone Slave

Piconet 2

Figure 5.11: Bluetooth Operation

File Synchronization

Client PCSlave

NotebookMaster

Printer SlavePrinting

Call Through CompanyPhone System

CellphoneMaster

Telephone Slave

Piconet 1

Piconet 2

Home Networks

Many Homes have more than one computer or Internet DeviceDon’t want to provide Internet to each

device independentlyConnect all device to a network and provide

Internet access to the Home networksSometimes 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

Wireless Media

Get rid of wiring PPP or Multihttp://

www.dlink.com/products/?pid=318

Wireless Speakers

Smart House

If your home has a network then can get Internet enabled applianceControl systems that you can access from

anywhereSecurity systems

Places to checkhttp://www.smarthomeusa.com/http://www.smarthome.com/index.html

For next class

Read through chapter 26 (page 187) Extra Credit Question on Next exam

How many Hackers have been arrested in Maine?

Can you name any successful prosecutions of Hackers in the state of Maine?

What is the problem in catching and prosecuting Hackers in Maine?