Wi Fi Technology

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  • 1. Wi-Fi Technology Alok Pandey
  • 2. Agenda
    • Introduction
    • Wi-Fi Technologies
    • Wi-Fi Architecture
    • Wi-Fi Network Elements
    • How a Wi-Fi Network Works
    • Wi-Fi Network Topologies
    • Wi-Fi Configurations
    • Applications of Wi-Fi
    • Wi-Fi Security
    • Advantages/ Disadvantages of Wi-Fi
  • 3. Introduction
    • Wireless Technology is an alternative to Wired Technology, which is commonly used, for connecting devices in wireless mode.
    • Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE 802.11 communications standard for Wireless Local Area Networks (WLANs).
    • Wi-Fi Network connect computers to each other, to the internet and to the wired network.
  • 4. The Wi-Fi Technology
    • Wi-Fi Networks use Radio Technologies to transmit & receive data at high speed:
      • IEEE 802.11b
      • IEEE 802.11a
      • IEEE 802.11g
  • 5. IEEE 802.11b
    • Appear in late 1999
    • Operates at 2.4GHz radio spectrum
    • 11 Mbps (theoretical speed) - within 30 m Range
    • 4-6 Mbps (actual speed)
    • 100 -150 feet range
    • Most popular, Least Expensive
    • Interference from mobile phones and Bluetooth devices which can reduce the transmission speed.
  • 6. IEEE 802.11a
    • Introduced in 2001
    • Operates at 5 GHz (less popular)
    • 54 Mbps (theoretical speed)
    • 15-20 Mbps (Actual speed)
    • 50-75 feet range
    • More expensive
    • Not compatible with 802.11b
  • 7. IEEE 802.11g
    • Introduced in 2003
    • Combine the feature of both standards (a,b)
    • 100-150 feet range
    • 54 Mbps Speed
    • 2.4 GHz radio frequencies
    • Compatible with ‘b’
  • 8. 802.11 Physical Layer
    • There are three sublayers in physical layer:
    • Direct Sequence Spread Spectrum (DSSS)
    • Frequency Hoping Spread Spectrum (FHSS)
    • Diffused Infrared (DFIR) - Wide angle
  • 9. DSSS
    • Direct sequence signaling technique divides the 2.4 GHz band into 11 22-MHz channels. Adjacent channels overlap one another partially, with three of the 11 being completely non-overlapping. Data is sent across one of these 22 MHz channels without hopping to other channels.
  • 10. IEEE 802.11 Data Link Layer
    • The data link layer consists of two sublayers :
      • Logical Link Control (LLC)
      • Media Access Control (MAC).
      • 802.11 uses the same 802.2 LLC and 48-bit addressing as other 802 LANs, allowing for very simple bridging from wireless to IEEE wired networks, but the MAC is unique to WLANs.
  • 11. 802.11 Media Access Control
    • Carrier Sense Medium Access with collision avoidance protocol (CSMA/CA)
      • Listen before talking
      • Avoid collision by explicit Acknowledgement (ACK)
      • Problem: additional overhead of ACK packets, so slow performance
    • Request to Send/Clear to Send (RTS/CTS) protocol
      • Solution for “hidden node” problem
      • Problem: Adds additional overhead by temporarily reserving the medium, so used for large size packets only retransmission would be expensive
  • 12. 802.11 Media Access Control(cont.)
    • Power Management
      • MAC supports power conservation to extend the battery life of portable devices
      • Power utilization modes
        • Continuous Aware Mode
          • Radio is always on and drawing power
        • Power Save Polling Mode
          • Radio is “dozing” with access point queuing any data for it
          • The client radio will wake up periodically in time to receive regular beacon signals from the access point.
          • The beacon includes information regarding which stations have traffic waiting for them
          • The client awake on beacon notification and receive its data
  • 13. 802.11 Media Access Control(cont.)
    • Fragmentation
    • CRC checksum
      • Each pkt has a CRC checksum calculated and attached to ensure that the data was not corrupted in transit
    • Association & Roaming
  • 14. Elements of a WI-FI Network
    • Access Point (AP) - The AP is a wireless LAN transceiver or “base station” that can connect one or many wireless devices simultaneously to the Internet.
    • Wi-Fi cards - They accept the wireless signal and relay information.They can be internal and external.(e.g PCMCIA Card for Laptop and PCI Card for Desktop PC)
    • Safeguards - Firewalls and anti-virus software protect networks from uninvited users and keep information secure.
  • 15. How a Wi-Fi Network Works
    • Basic concept is same as Walkie talkies.
    • A Wi-Fi hotspot is created by installing an access point to an internet connection.
    • An access point acts as a base station.
    • When Wi-Fi enabled device encounters a hotspot the device can then connect to that network wirelessly.
    • A single access point can support up to 30 users and can function within a range of 100 – 150 feet indoors and up to 300 feet outdoors.
    • Many access points can be connected to each other via Ethernet cables to create a single large network.
  • 16. Wi-Fi Network Topologies
    • AP-based topology (Infrastructure Mode)
    • Peer-to-peer topology (Ad-hoc Mode)
    • Point-to-multipoint bridge topology
  • 17. AP-based topology
    • The client communicate through Access Point.
    • BSA-RF coverage provided by an AP.
    • ESA-It consists of 2 or more BSA.
    • ESA cell includes 10-15% overlap to allow roaming.
  • 18. Peer-to-peer topology
    • AP is not required.
    • Client devices within a cell can communicate directly with each other.
    • It is useful for setting up of a wireless network quickly and easily.
  • 19. Point-to-multipoint bridge topology
    • This is used to connect a LAN in one building to a LANs in other buildings even if the buildings are miles apart.These conditions receive a clear line of sight between buildings. The line-of-sight range varies based on the type of wireless bridge and antenna used as well as the environmental conditions.
  • 20. Wi-Fi Configurations
  • 21. Wi-Fi Configurations
  • 22. Wi-Fi Configurations
  • 23. Wi-Fi Applications
    • Home
    • Small Businesses or SOHO
    • Large Corporations & Campuses
    • Health Care
    • Wireless ISP (WISP)
    • Travellers
  • 24. Wi-Fi Security Threats
    • Wireless technology doesn’t remove any old security issues, but introduces new ones
      • Eavesdropping
      • Man-in-the-middle attacks
      • Denial of Service
  • 25. Eavesdropping
    • Easy to perform, almost impossible to detect
    • By default, everything is transmitted in clear text
      • Usernames, passwords, content ...
      • No security offered by the transmission medium
    • Different tools available on the internet
      • Network sniffers, protocol analysers . . .
      • Password collectors
    • With the right equipment, it’s possible to eavesdrop traffic from few kilometers away
  • 26. MITM Attack
    • Attacker spoofes a disassociate message from the victim
    • The victim starts to look for a new access point, and the attacker advertises his own AP on a different channel, using the real AP’s MAC address
    • The attacker connects to the real AP using victim’s MAC address
  • 27. Denial of Service
    • Attack on transmission frequecy used
      • Frequency jamming
      • Not very technical, but works
    • Attack on MAC layer
      • Spoofed deauthentication / disassociation messages
      • can target one specific user
    • Attacks on higher layer protocol (TCP/IP protocol)
      • SYN Flooding
  • 28. Wi-Fi Security
    • The requirements for Wi-Fi network security can be broken down into two primary components:
    • Authentication
      • User Authentication
      • Server Authentication
    • Privacy
  • 29. Authentication
    • Keeping unauthorized users off the network
    • User Authentication
      • Authentication Server is used
      • Username and password
      • Risk:
        • Data (username & password) send before secure channel established
        • Prone to passive eavesdropping by attacker
      • Solution
        • Establishing a encrypted channel before sending username and password
  • 30. Authentication (cont..)
    • Server Authentication
      • Digital Certificate is used
      • Validation of digital certificate occurs automatically within client software
  • 31. Wi-Fi Security Techniques
      • Service Set Identifier (SSID)
      • Wired Equivalent Privacy (WEP)
      • 802.1X Access Control
      • Wireless Protected Access (WPA)
      • IEEE 802.11i
  • 32. Service Set Identifier (SSID)
    • SSID is used to identify an 802.11 network
    • It can be pre-configured or advertised in beacon broadcast
    • It is transmitted in clear text
      • Provide very little security
  • 33. Wired Equivalent Privacy (WEP)
    • Provide same level of security as by wired network
    • Original security solution offered by the IEEE 802.11 standard
    • Uses RC4 encryption with pre-shared keys and 24 bit initialization vectors (IV)
    • key schedule is generated by concatenating the shared secret key with a random generated 24-bit IV
    • 32 bit ICV (Integrity check value)
    • No. of bits in keyschedule is equal to sum of length of the plaintext and ICV
  • 34. Wired Equivalent Privacy (WEP) (cont.)
    • 64 bit preshared key-WEP
    • 128 bit preshared key-WEP2
    • Encrypt data only between 802.11 stations.once it enters the wired side of the network (between access point) WEP is no longer valid
    • Security Issue with WEP
      • Short IV
      • Static key
    • Offers very little security at all
  • 35. 802.1x Access Control
    • Designed as a general purpose network access control mechanism
      • Not Wi-Fi specific
    • Authenticate each client connected to AP (for WLAN) or switch port (for Ethernet)
    • Authentication is done with the RADIUS server, which ”tells” the access point whether access to controlled ports should be allowed or not
      • AP forces the user into an unauthorized state
      • user send an EAP start message
      • AP return an EAP message requesting the user’s identity
      • Identity send by user is then forwared to the authentication server by AP
      • Authentication server authenticate user and return an accept or reject message back to the AP
      • If accept message is return, the AP changes the client’s state to authorized and normal traffic flows
  • 36. 802.1x Access Control
  • 37. Wireless Protected Access (WPA)
    • WPA is a specification of standard based, interoperable security enhancements that strongly increase the level of data protection and access control for existing and future wireless LAN system.
    • User Authentication
      • 802.1x
      • EAP
    • TKIP (Temporal Key Integrity Protocol) encryption
      • RC4, dynamic encryption keys (session based)
        • 48 bit IV
        • per packet key mixing function
      • Fixes all issues found from WEP
    • Uses Message Integrity Code (MIC) Michael
      • Ensures data integrity
    • Old hardware should be upgradeable to WPA
  • 38. Wireless Protected Access (WPA)(cont.)
    • WPA comes in two flavors
      • WPA-PSK
        • use pre-shared key
        • For SOHO environments
        • Single master key used for all users
      • WPA Enterprise
        • For large organisation
        • Most secure method
        • Unique keys for each user
        • Separate username & password for each user
  • 39. WPA and Security Threats
      • Data is encrypted
        • Protection against eavesdropping and man-in-the-middle attacks
      • Denial of Service
        • Attack based on fake massages can not be used.
        • As a security precaution, if WPA equipment sees two packets with invalid MICs within a second, it disassociates all its clients, and stops all activity for a minute
        • Only two packets a minute enough to completely stop a wireless network
  • 40. 802.11i
    • Provides standard for WLAN security
    • Authentication
      • 802.1x
    • Data encryption
      • AES protocol is used
    • Secure fast handoff-This allow roaming between APs without requiring client to fully reauthenticate to every AP.
    • Will require new hardware
  • 41. Advantages
    • Mobility
    • Ease of Installation
    • Flexibility
    • Cost
    • Reliability
    • Security
    • Use unlicensed part of the radio spectrum
    • Roaming
    • Speed
  • 42. Limitations
    • Interference
    • Degradation in performance
    • High power consumption
    • Limited range