802.11 Networks  Olga Agnew Bryant Likes Daewon Seo
Agenda <ul><li>Bryant: 802.11 Overview </li></ul><ul><li>Bryant: 802.11b </li></ul><ul><li>Olga: 802.11a </li></ul><ul><li...
Why wireless? <ul><li>Mobility </li></ul><ul><li>Flexibility </li></ul><ul><li>Can be more cost effective </li></ul>
802.3 Ethernet Networks <ul><li>Ethernet networks make up 95% of LANs </li></ul><ul><li>Ethernet  </li></ul><ul><ul><li>Ne...
802.11 Wireless Networks <ul><li>802.11 builds on Ethernet </li></ul><ul><li>802.11 </li></ul><ul><ul><li>Network Interfac...
802.11 Components <ul><li>Distribution System </li></ul><ul><li>Access Points </li></ul><ul><li>Wireless Medium </li></ul>...
802.11 Topologies <ul><li>Independent networks </li></ul><ul><li>Infrastructure networks </li></ul>Access Point
Wireless Bridging <ul><li>Can also be setup as a bridge </li></ul><ul><li>(Yagi directional antenna) </li></ul>Access Poin...
802.11 Media Access Control <ul><li>Ethernet uses CSMA/CD </li></ul><ul><li>802.11 uses CSMA/CA </li></ul><ul><ul><li>Dist...
802.11 Network Operations <ul><li>Distribution </li></ul><ul><ul><li>Deliver messages to their destination </li></ul></ul>...
802.11 Network Operations <ul><li>Association </li></ul><ul><ul><li>“ Plugs” stations into the network </li></ul></ul><ul>...
802.11 Network Operations <ul><li>Authentication </li></ul><ul><ul><li>Prevents unauthorized use </li></ul></ul><ul><li>De...
802.11b
802.11b - Data Transmission <ul><li>Transmit 300 to 500 feet </li></ul><ul><li>Frequency-hopping spread-spectrum (FHSS) </...
802.11b –  Frequencies and Bandwidth <ul><li>2.4000 to 2.4835 GHz frequency </li></ul><ul><li>22 MHz bandwidth per channel...
802.11b - Transmission <ul><li>1 and 2 Mbps speeds </li></ul><ul><ul><li>Use 11-bit Barker sequence </li></ul></ul><ul><li...
802.11a
802.11a <ul><li>Why did ‘a’ come before ‘b’? </li></ul><ul><li>Is it different? </li></ul><ul><li>Is it better? </li></ul>...
802.11a - Data Transmission <ul><li>Transmit 100 to 150 feet </li></ul><ul><li>Orthogonal Frequency-Division Multiplexing ...
802.11a -  Frequencies and Bandwidth <ul><li>5 - GHz frequency </li></ul><ul><li>12 channels </li></ul><ul><ul><li>20 MHz ...
802.11a - Transmission <ul><li>6 and 9 Mbps speeds </li></ul><ul><ul><li>Use 24-bit Barker sequence </li></ul></ul><ul><ul...
Comparison <ul><li>Physical Layer </li></ul><ul><ul><ul><li>802.11b 802.11a </li></ul></ul></ul><ul><li>OFDM </li></ul><ul...
Comparison (cont’d) <ul><li>Physical Layer </li></ul><ul><ul><ul><li>802.11b 802.11a </li></ul></ul></ul><ul><li>OFDM (con...
Conclusion <ul><li>Is faster really better?  </li></ul><ul><li>What are the application needs? </li></ul><ul><ul><ul><li>B...
Conclusion (Cont’d) <ul><li>Additional factors to consider: </li></ul><ul><ul><li>2.4 GHz frequency shared by: </li></ul><...
802.11 Security Overview
Overview of 802.11 Security <ul><li>Not long ago  </li></ul><ul><ul><li>Wireless security was an afterthought (new and rar...
Same risks as Wired-LANs? <ul><li>Threat to physical security of a network </li></ul><ul><ul><li>Denial of service and sab...
802.11 Security Mechanisms <ul><li>Authentication through… </li></ul><ul><ul><li>Open system </li></ul></ul><ul><ul><li>Sh...
Authentication <ul><li>Open systems </li></ul><ul><ul><li>Do not provide authentication </li></ul></ul><ul><ul><li>Only id...
Authentication (Continued) <ul><li>Shared key authentication </li></ul>
Authentication (Continued) <ul><li>Shared key authentication… </li></ul><ul><ul><li>It is delivered to participating stati...
WEP Encryption <ul><li>802.11-Level of data confidentiality is equivalent to a wired network </li></ul><ul><li>Use-RC4 sym...
WEP Encryption (Cont) <ul><li>Provide data integrity from random errors (Integrity Check Value) </li></ul><ul><li>The dete...
WEP Encryption (Cont) <ul><li>All wireless APs and Clients use the same configured WEP key for multiple connection and aut...
Security Summary <ul><li>The lack of automated authentication and key determination cause problems in shared communication...
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  1. 1. 802.11 Networks Olga Agnew Bryant Likes Daewon Seo
  2. 2. Agenda <ul><li>Bryant: 802.11 Overview </li></ul><ul><li>Bryant: 802.11b </li></ul><ul><li>Olga: 802.11a </li></ul><ul><li>Olga: Comparison - 802.11b and 802.11a </li></ul><ul><li>Daewon: Security </li></ul>
  3. 3. Why wireless? <ul><li>Mobility </li></ul><ul><li>Flexibility </li></ul><ul><li>Can be more cost effective </li></ul>
  4. 4. 802.3 Ethernet Networks <ul><li>Ethernet networks make up 95% of LANs </li></ul><ul><li>Ethernet </li></ul><ul><ul><li>Network Interface Cards (NIC) </li></ul></ul><ul><ul><li>Network Cables </li></ul></ul><ul><ul><li>Hubs </li></ul></ul>
  5. 5. 802.11 Wireless Networks <ul><li>802.11 builds on Ethernet </li></ul><ul><li>802.11 </li></ul><ul><ul><li>Network Interface Cards (NIC) </li></ul></ul><ul><ul><li>Air </li></ul></ul><ul><ul><li>Access Points </li></ul></ul>
  6. 6. 802.11 Components <ul><li>Distribution System </li></ul><ul><li>Access Points </li></ul><ul><li>Wireless Medium </li></ul><ul><li>Stations </li></ul>Distribution System Access Point Station Wireless Medium
  7. 7. 802.11 Topologies <ul><li>Independent networks </li></ul><ul><li>Infrastructure networks </li></ul>Access Point
  8. 8. Wireless Bridging <ul><li>Can also be setup as a bridge </li></ul><ul><li>(Yagi directional antenna) </li></ul>Access Point Access Point
  9. 9. 802.11 Media Access Control <ul><li>Ethernet uses CSMA/CD </li></ul><ul><li>802.11 uses CSMA/CA </li></ul><ul><ul><li>Distributed Coordination Function (DCF) </li></ul></ul><ul><ul><ul><li>Low overhead </li></ul></ul></ul><ul><ul><li>Point Coordination Function (PCF) </li></ul></ul><ul><ul><ul><li>Avoids the hidden node problem </li></ul></ul></ul>
  10. 10. 802.11 Network Operations <ul><li>Distribution </li></ul><ul><ul><li>Deliver messages to their destination </li></ul></ul><ul><ul><li>All messages use this service </li></ul></ul><ul><li>Integration </li></ul><ul><ul><li>Connects the wireless network to the wired network </li></ul></ul>
  11. 11. 802.11 Network Operations <ul><li>Association </li></ul><ul><ul><li>“ Plugs” stations into the network </li></ul></ul><ul><li>Reassociation </li></ul><ul><ul><li>Switching to another AP with better service </li></ul></ul><ul><li>Disassociation </li></ul><ul><ul><li>Association no longer needed </li></ul></ul>
  12. 12. 802.11 Network Operations <ul><li>Authentication </li></ul><ul><ul><li>Prevents unauthorized use </li></ul></ul><ul><li>Deauthentication </li></ul><ul><ul><li>Terminates authenticated relationship </li></ul></ul><ul><li>Privacy </li></ul><ul><ul><li>Wired Equivalency Privacy (WEP) </li></ul></ul><ul><li>MAC Service Data Unit (MSDU) Delivery </li></ul><ul><ul><li>Destination delivery </li></ul></ul>
  13. 13. 802.11b
  14. 14. 802.11b - Data Transmission <ul><li>Transmit 300 to 500 feet </li></ul><ul><li>Frequency-hopping spread-spectrum (FHSS) </li></ul><ul><ul><li>1 or 2 Mbps </li></ul></ul><ul><li>Direct-sequence spread-spectrum (DSSS) </li></ul><ul><ul><li>1, 2, 5.5, or 11 Mbps </li></ul></ul>
  15. 15. 802.11b – Frequencies and Bandwidth <ul><li>2.4000 to 2.4835 GHz frequency </li></ul><ul><li>22 MHz bandwidth per channel </li></ul><ul><li>3 MHz guardbands </li></ul><ul><li>Analog radio signal (NIC is modem) </li></ul>
  16. 16. 802.11b - Transmission <ul><li>1 and 2 Mbps speeds </li></ul><ul><ul><li>Use 11-bit Barker sequence </li></ul></ul><ul><li>5.5 and 11 Mbps speeds </li></ul><ul><ul><li>Use complementary code keying (CCK) </li></ul></ul>
  17. 17. 802.11a
  18. 18. 802.11a <ul><li>Why did ‘a’ come before ‘b’? </li></ul><ul><li>Is it different? </li></ul><ul><li>Is it better? </li></ul><ul><li>Is it faster? </li></ul>
  19. 19. 802.11a - Data Transmission <ul><li>Transmit 100 to 150 feet </li></ul><ul><li>Orthogonal Frequency-Division Multiplexing (OFDM) </li></ul><ul><ul><li>6 to 54 Mbps </li></ul></ul>
  20. 20. 802.11a - Frequencies and Bandwidth <ul><li>5 - GHz frequency </li></ul><ul><li>12 channels </li></ul><ul><ul><li>20 MHz bandwidth per channel </li></ul></ul><ul><ul><li>Broken into 52 separate channels </li></ul></ul><ul><ul><ul><li>48 transmit, 4 used for control </li></ul></ul></ul>
  21. 21. 802.11a - Transmission <ul><li>6 and 9 Mbps speeds </li></ul><ul><ul><li>Use 24-bit Barker sequence </li></ul></ul><ul><ul><ul><li>Converted to 1 OFDM symbol of 48 bits </li></ul></ul></ul><ul><li>12, 24 and 48 Mbps speeds </li></ul><ul><ul><li>Use binary phase shift keying (BPSK) </li></ul></ul>
  22. 22. Comparison <ul><li>Physical Layer </li></ul><ul><ul><ul><li>802.11b 802.11a </li></ul></ul></ul><ul><li>OFDM </li></ul><ul><li>12 – 20 MHz channels </li></ul><ul><li>Data rates: up to 54 </li></ul><ul><li>Mbps (12-24 is norm) </li></ul><ul><li>DSSS </li></ul><ul><li>3 - 22 MHz channels </li></ul><ul><li>Data Rates: up to 11 </li></ul><ul><li>Mbps (5.5 is norm) </li></ul>
  23. 23. Comparison (cont’d) <ul><li>Physical Layer </li></ul><ul><ul><ul><li>802.11b 802.11a </li></ul></ul></ul><ul><li>OFDM (cont’d) </li></ul><ul><li>Frequency Range: </li></ul><ul><li>up to 150 Feet </li></ul><ul><li>DSSS (cont’d) </li></ul><ul><li>Frequency Range </li></ul><ul><li>up to 300 Feet </li></ul>
  24. 24. Conclusion <ul><li>Is faster really better? </li></ul><ul><li>What are the application needs? </li></ul><ul><ul><ul><li>Better for higher end apps </li></ul></ul></ul><ul><ul><ul><ul><li>Video, Voice, transmission of large image or large files, etc. </li></ul></ul></ul></ul><ul><ul><ul><li>Shorter distance </li></ul></ul></ul><ul><li>Remember…“There’s always a trade-off” </li></ul>
  25. 25. Conclusion (Cont’d) <ul><li>Additional factors to consider: </li></ul><ul><ul><li>2.4 GHz frequency shared by: </li></ul></ul><ul><ul><ul><li>wireless phones, microwave ovens </li></ul></ul></ul><ul><ul><ul><li>Bluetooth devices, others… </li></ul></ul></ul><ul><ul><li>Combo-cards now available </li></ul></ul><ul><ul><ul><li>Proxim’s </li></ul></ul></ul>
  26. 26. 802.11 Security Overview
  27. 27. Overview of 802.11 Security <ul><li>Not long ago </li></ul><ul><ul><li>Wireless security was an afterthought (new and rare) </li></ul></ul><ul><li>Now </li></ul><ul><ul><li>Security issues became more vital (available for anyone and cheap) </li></ul></ul>
  28. 28. Same risks as Wired-LANs? <ul><li>Threat to physical security of a network </li></ul><ul><ul><li>Denial of service and sabotage </li></ul></ul><ul><li>Unauthorized access and eavesdropping </li></ul><ul><li>Attacks form within the network’s user community </li></ul><ul><ul><li>Employees have been known to read, distribute, and alter valuable company data </li></ul></ul>
  29. 29. 802.11 Security Mechanisms <ul><li>Authentication through… </li></ul><ul><ul><li>Open system </li></ul></ul><ul><ul><li>Shared key authentication </li></ul></ul><ul><li>Data confidentiality through… </li></ul><ul><ul><li>Wired Equivalent Privacy (WEP) </li></ul></ul>
  30. 30. Authentication <ul><li>Open systems </li></ul><ul><ul><li>Do not provide authentication </li></ul></ul><ul><ul><li>Only identification using the wireless adapter’s MAC address </li></ul></ul><ul><ul><li>Access can be based on MAC address </li></ul></ul><ul><ul><li>MAC address of wireless client can be spoofed </li></ul></ul><ul><li>Overall, the open system is not secure. </li></ul>
  31. 31. Authentication (Continued) <ul><li>Shared key authentication </li></ul>
  32. 32. Authentication (Continued) <ul><li>Shared key authentication… </li></ul><ul><ul><li>It is delivered to participating station through a secure channel that is independent of IEEE 802.11 </li></ul></ul><ul><ul><li>The secret of shared key is manually configured for both the wireless AP and client </li></ul></ul><ul><ul><li>Securing physical access to the network is difficult </li></ul></ul><ul><ul><li>Anyone within range of wireless AP can listen other users’ data </li></ul></ul><ul><li>In the overall, this authentication is not secure and is not recommended for use </li></ul>
  33. 33. WEP Encryption <ul><li>802.11-Level of data confidentiality is equivalent to a wired network </li></ul><ul><li>Use-RC4 symmetrical stream cipher(40-bit or 104-bit encryption key) </li></ul>
  34. 34. WEP Encryption (Cont) <ul><li>Provide data integrity from random errors (Integrity Check Value) </li></ul><ul><li>The determination and distribution of WEP keys are not defined text string must be manually configured </li></ul><ul><li>There is no defined mechanism to change the WEP key </li></ul>
  35. 35. WEP Encryption (Cont) <ul><li>All wireless APs and Clients use the same configured WEP key for multiple connection and authentication-it is possible for a malicious users to remotely capture WEP cipher text- problem of security </li></ul><ul><li>The lack of WEP key management – cause change in WEP key frequently </li></ul>
  36. 36. Security Summary <ul><li>The lack of automated authentication and key determination cause problems in shared communication </li></ul><ul><li>WEP never be totally secure, and 802.11 security will not be secure either </li></ul><ul><li>New versions of 802.11 is focus on new encryption, authentication and key exchange algorithm for better security </li></ul><ul><li>802.11 security is being investigated for better protection from all attacks </li></ul>
  37. 37. Questions?
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