1. Wi-Fi Technology

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 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 b
IEEE a
IEEE g

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)
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 b

7. IEEE g
Introduced in 2003
Combine the feature of both standards (a,b)
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 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 Data Link Layer
The data link layer consists of two sublayers :
Logical Link Control (LLC)
Media Access Control (MAC).
uses the same 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. 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 i

32. Service Set Identifier (SSID)
SSID is used to identify an 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 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 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