1. Wi-Fi Technology
By : Pranav Mandora
Rikin Mistry
LDRP-EC

2. Agenda Introduction Wi-Fi Technologies Wi-Fi Architecture
Wi-Fi Network Elements
How a Wi-Fi Network Works
Wi-Fi Network Topologies
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).

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

12. 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.

13. 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.

14. Wi-Fi Network Topologies
AP-based topology (Infrastructure Mode)
Peer-to-peer topology (Ad-hoc Mode)
Point-to-multipoint bridge topology

15. 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.

16. 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.

17. 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.

18. Wi-Fi Applications Home Small Businesses or SOHO
Large Corporations & Campuses
Health Care
Wireless ISP (WISP)
Travellers

19. 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

20. 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

21. 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

22. Denial of Service Attack on transmission frequecy used
Frequency jamming
Not very technical, but works
can target one specific user

23. 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

24. Advantages Mobility Ease of Installation Flexibility Cost Reliability
Security
Use unlicensed part of the radio spectrum
Roaming
Speed

25. Limitations Interference Degradation in performance
High power consumption
Limited range

26. Thanks