Introduction
The
Camille CAPELLE Romain DAMASE Aymeric HERVIEU Matthieu REISZ
Ozone – WiFi provider coverage
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History of wireless LAN
• 1898: first wireless transmition in France • 1922: Born of BBC • 1972:
– First wireless lan by scientists of Hawaii – First users were militaries
PLAN
1. Wireless networks 2. Physic aspects of wireless networks 3. Security
• 1999: foundation of the WECA or WiFi‐alliance • 2003: apparition of Wireless LAN in Pau & Paris
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The Wireless Technology 1. Wireless networks
Generalities
• 4 categories:
o Wireless Personal Area Network (WPAN) o Wireless Local Area Network (WLAN) o Wireless Metropolitan Area Network (WMAN) o Wireless Wide Area Network (WWAN)
• 2 technologies in competition: WLAN and WMAN
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WiFi (WLAN)
• IEEE 802.11 standard • Theoretical rate: from 11 Mb/s to 54 Mb/s • How to set up a WiFi network?
o Infrastructure mode o "Ad‐Hoc" mode
Advantages and drawbacks
Infra. mode
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ad-hoc mode
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The WiMax (WMAN)
• WiMax: Worldwide Interoperability for Microwave Access
o The IEEE 802.16 standard
• Rates:
o Theoretical rate: about 70 Mb/s under 50 km o Real rate: about 10 Mb/s under 10 km with obstacles
2. Physical aspects of wireless networks
How does it work?
• Objective: rate as WiFi or better but mobility as cell phone
o Base Transceiver Station (BTS)
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Current WiFi norms (1)
• Define the 2 lowest OSI layers
o Physical: electrical and physical specifications o Data Link: data transfers between network entities
Norm 802.11a 802.11b 802.11g
Current WiFi norms (2)
Frequency 5 GHz 2.4 GHz 2.4 GHz Rate 54 Mb/s 11 Mb/s 54 Mb/s Inside coverage 10 m 50 m 25 m Outside coverage ‐ 200 m 75 m
• Radio signals sent in frequency narrow bands • Authorized and usable frequencies (Europe)
o 2.400 to 2.4835 GHz o 5.725 to 5.880 GHz
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• The lower is the frequency, the more efficient is the transmission
o Better coverage o Better efficacy in crossing obstructions
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Rate losses
• Always a difference between theoretical and real rates:
o Material dysfunction o Firewall o Interferences: ‐ other networks ‐ device using the same frequency (microwave) o Obstructions: ‐ Wall ‐ Water (rain, fog)
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802.11n and MIMO technology (1)
• User’s needs increase: video streams, large file transfers, online games…
New norm with a technology called “Multiple In, Multiple Out”
• Aim:
o Backward compatibility o Higher rate o Close to wire network performances
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802.11n and MIMO technology (2)
• Problem : not possible to use new frequencies or increase them • Solution:
– Several duplicate signals sent in various directions – Superposition principle
increase rates and coverage
802.11n and MIMO technology (3)
• First drafts
o Draft 1.0: April 2006 o Draft 2.0: March 2007 already some existing devices
• Final revision: 2008
o Theoretical rate ≈ 540 Mb/s o Coverage ≈ 100 m
• Use a chip for the signal reconstruction
will be able to choose dynamically the directions
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• End of wire networks?
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Why do we speak more about security concerning the WiFi ?
• CAUSES:
3. Security
What are the risks? How to secure a network?
o The waves can go in all directions without any control
• CONSEQUENCES:
o Some people with bad intentions can intercept confidential informations from the network
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a. The risks
• Data interception • Network intrusion • Denial of service • The war driving
Opened and connected network Opened network Secured network
b. Secure your network
• • • • Adapt your WiFi area Change default settings Filter the MAC addresses Confidential exchange:
o WEP: Wired Equivalent Privacy o WPA: Wifi Protected Access
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WEP against WPA
WEP • Key : 64 bits • Old algorithm • 5 hours to crack WPA • Key : 128 bits • New algorithm : TKIP • Sure for the moment
Conclusion (1)
• Technology among others ( WiMAX … ) • Flexible and easy to install • Differences between reality and theory • Less secure than Ethernet
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Conclusion (2)
• Today where are we with WiFi ?
– Many hotspots: more than 31 000 in France (2003) – Some boxes include the option hotspot – Apparition of WiFi on cellular – Many gadgets use WiFi
• Game console • Cell phone • Rabbit WiFi : Nabaztag
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