Wi-Fi Technology

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 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).

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

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