Wi-Fi TechnologyWi-Fi Technology

By : Pranav MandoraRikin MistryLDRP-EC

AgendaAgenda

• IntroductionIntroduction• Wi-Fi TechnologiesWi-Fi Technologies• Wi-Fi ArchitectureWi-Fi Architecture• Wi-Fi Network ElementsWi-Fi Network Elements• How a Wi-Fi Network WorksHow a Wi-Fi Network Works• Wi-Fi Network TopologiesWi-Fi Network Topologies• Applications of Wi-FiApplications of Wi-Fi• Wi-Fi SecurityWi-Fi Security• Advantages/ Disadvantages of Wi-FiAdvantages/ Disadvantages of Wi-Fi

IntroductionIntroduction• Wireless Technology is an alternative to Wired Wireless Technology is an alternative to Wired

Technology, which is commonly used, for Technology, which is commonly used, for connecting devices in wireless mode.connecting devices in wireless mode.

• Wi-Fi (Wireless Fidelity) is a generic term that Wi-Fi (Wireless Fidelity) is a generic term that refers to the IEEE 802.11 communications refers to the IEEE 802.11 communications standard for Wireless Local Area Networks standard for Wireless Local Area Networks (WLANs).(WLANs).

• Wi-Fi Network connect computers to each other, Wi-Fi Network connect computers to each other, to the internet and to the wired network.to the internet and to the wired network.

The Wi-Fi TechnologyThe Wi-Fi Technology

Wi-Fi Networks use Radio Technologies to Wi-Fi Networks use Radio Technologies to transmit & receive data at high speed:transmit & receive data at high speed:

• IEEE 802.11bIEEE 802.11b• IEEE 802.11aIEEE 802.11a• IEEE 802.11gIEEE 802.11g

IEEE 802.11bIEEE 802.11b

• Appear in late 1999Appear in late 1999• Operates at 2.4GHz radio spectrumOperates at 2.4GHz radio spectrum• 11 Mbps (theoretical speed) - within 30 m Range11 Mbps (theoretical speed) - within 30 m Range• 4-6 Mbps (actual speed)4-6 Mbps (actual speed)• 100 -150 feet range100 -150 feet range• Most popular, Least ExpensiveMost popular, Least Expensive• Interference from mobile phones and Bluetooth Interference from mobile phones and Bluetooth

devices which can reduce the transmission devices which can reduce the transmission speed.speed.

IEEE 802.11aIEEE 802.11a

• Introduced in 2001Introduced in 2001• Operates at 5 GHz (less popular) Operates at 5 GHz (less popular) • 54 Mbps (theoretical speed)54 Mbps (theoretical speed)• 15-20 Mbps (Actual speed)15-20 Mbps (Actual speed)• 50-75 feet range50-75 feet range• More expensiveMore expensive• Not compatible with 802.11bNot compatible with 802.11b

IEEE 802.11gIEEE 802.11g

• Introduced in 2003Introduced in 2003• Combine the feature of both standards Combine the feature of both standards

(a,b)(a,b)• 100-150 feet range100-150 feet range• 54 Mbps Speed54 Mbps Speed• 2.4 GHz radio frequencies2.4 GHz radio frequencies• Compatible with ‘b’Compatible with ‘b’

802.11 Physical Layer802.11 Physical Layer

There are three sublayers in physical layer:There are three sublayers in physical layer:

• Direct Sequence Spread Spectrum (DSSS)Direct Sequence Spread Spectrum (DSSS)• Frequency Hoping Spread Spectrum (FHSS)Frequency Hoping Spread Spectrum (FHSS)• Diffused Infrared (DFIR) - Wide angleDiffused Infrared (DFIR) - Wide angle

DSSSDSSS• Direct sequence signaling technique divides the 2.4 GHz band into Direct sequence signaling technique divides the 2.4 GHz band into

11 22-MHz channels. Adjacent channels overlap one another 22-MHz channels. Adjacent channels overlap one another partially, with three of the 11 being completely non-overlapping. partially, with three of the 11 being completely non-overlapping. Data is sent across one of these 22 MHz channels without hopping Data is sent across one of these 22 MHz channels without hopping to other channels.to other channels.

IEEE 802.11 Data Link LayerIEEE 802.11 Data Link Layer

The data link layer consists of two sublayers : The data link layer consists of two sublayers :

• Logical Link Control (LLC) Logical Link Control (LLC) • Media Access Control (MAC).Media Access Control (MAC).

802.11 Media Access Control802.11 Media Access Control

• Carrier Sense Medium Access with collision Carrier Sense Medium Access with collision avoidance protocol (CSMA/CA)avoidance protocol (CSMA/CA)• Listen before talkingListen before talking• Avoid collision by explicit Acknowledgement (ACK)Avoid collision by explicit Acknowledgement (ACK)• Problem: additional overhead of ACK packets, so Problem: additional overhead of ACK packets, so

slow performance slow performance

Elements of a WI-FI NetworkElements of a WI-FI Network

• Access Point (AP) - Access Point (AP) - The AP is a wireless LAN The AP is a wireless LAN transceiver or “base station” that can connect one or many transceiver or “base station” that can connect one or many wireless devices simultaneously to the Internet. wireless devices simultaneously to the Internet.

• Wi-Fi cards - Wi-Fi cards - They accept the wireless signal and relay They accept the wireless signal and relay information.They can be internal and external.(e.g PCMCIA information.They can be internal and external.(e.g PCMCIA Card for Laptop and PCI Card for Desktop PC)Card for Laptop and PCI Card for Desktop PC)

• Safeguards - Safeguards - Firewalls and anti-virus software protect Firewalls and anti-virus software protect networks from uninvited users and keep information secure.networks from uninvited users and keep information secure.

How a Wi-Fi Network WorksHow a Wi-Fi Network Works

• Basic concept is same as Walkie talkies.Basic concept is same as Walkie talkies.• A Wi-Fi hotspot is created by installing an access point A Wi-Fi hotspot is created by installing an access point

to an internet connection.to an internet connection.• An access point acts as a base station. An access point acts as a base station. • When Wi-Fi enabled device encounters a hotspot the When Wi-Fi enabled device encounters a hotspot the

device can then connect to that network wirelessly.device can then connect to that network wirelessly.• A single access point can support up to 30 users and A single access point can support up to 30 users and

can function within a range of 100 – 150 feet indoors and can function within a range of 100 – 150 feet indoors and up to 300 feet outdoors.up to 300 feet outdoors.

• Many access points can be connected to each other via Many access points can be connected to each other via Ethernet cables to create a single large network.Ethernet cables to create a single large network.

Wi-Fi Network TopologiesWi-Fi Network Topologies

• AP-based topology (Infrastructure Mode)AP-based topology (Infrastructure Mode)

• Peer-to-peer topology (Ad-hoc Mode)Peer-to-peer topology (Ad-hoc Mode)

• Point-to-multipoint bridge topologyPoint-to-multipoint bridge topology

AP-based topologyAP-based topology• The client communicate through Access Point. The client communicate through Access Point. • BSA-RF coverage provided by an AP.BSA-RF coverage provided by an AP.• ESA-It consists of 2 or more BSA.ESA-It consists of 2 or more BSA.• ESA cell includes 10-15% overlap to allow ESA cell includes 10-15% overlap to allow

roaming.roaming.

Peer-to-peer topologyPeer-to-peer topology• AP is not required.AP is not required.• Client devices within Client devices within

a cell can a cell can communicate directly communicate directly with each other.with each other.

• It is useful for setting It is useful for setting up of a wireless up of a wireless network quickly and network quickly and easily.easily.

Point-to-multipoint bridge topologyPoint-to-multipoint bridge topologyThis is used to connect a LAN in one building to a LANs This is used to connect a LAN in one building to a LANs in other buildings even if the buildings are miles in other buildings even if the buildings are miles apart.These conditions receive a clear line of sight apart.These conditions receive a clear line of sight between buildings. The line-of-sight range varies based between buildings. The line-of-sight range varies based on the type of wireless bridge and antenna used as well on the type of wireless bridge and antenna used as well as the environmental conditions.as the environmental conditions.

Wi-Fi ApplicationsWi-Fi Applications

• HomeHome• Small Businesses or SOHOSmall Businesses or SOHO• Large Corporations & CampusesLarge Corporations & Campuses• Health CareHealth Care• Wireless ISP (WISP)Wireless ISP (WISP)• TravellersTravellers

Wi-Fi Security ThreatsWi-Fi Security Threats

• Wireless technology doesn’t remove any Wireless technology doesn’t remove any old security issues, but introduces new old security issues, but introduces new onesones• EavesdroppingEavesdropping• Man-in-the-middle attacksMan-in-the-middle attacks• Denial of ServiceDenial of Service

EavesdroppingEavesdropping

• Easy to perform, almost impossible to Easy to perform, almost impossible to detectdetect

• By default, everything is transmitted in By default, everything is transmitted in clear textclear text• Usernames, passwords, content ...Usernames, passwords, content ...• No security offered by the transmission No security offered by the transmission

mediummedium

MITM AttackMITM Attack

1.1. Attacker spoofes a Attacker spoofes a disassociate message disassociate message from the victimfrom the victim

2.2. The victim starts to The victim starts to look for a new access look for a new access point, and the attacker point, and the attacker advertises his own AP advertises his own AP on a different channel, on a different channel, using the real AP’s using the real AP’s MAC addressMAC address

3.3. The attacker connects The attacker connects to the real AP using to the real AP using victim’s MAC addressvictim’s MAC address

Denial of ServiceDenial of Service

• Attack on transmission frequecy usedAttack on transmission frequecy used• Frequency jammingFrequency jamming• Not very technical, but worksNot very technical, but works• can target one specific usercan target one specific user

WPA and Security ThreatsWPA and Security Threats

• Data is encryptedData is encrypted• Protection against eavesdropping and man-in-the-Protection against eavesdropping and man-in-the-

middle attacksmiddle attacks

• Denial of ServiceDenial of Service• Attack based on fake massages can not be used.Attack based on fake massages can not be used.• As a security precaution, if WPA equipment sees As a security precaution, if WPA equipment sees

two packets with invalid MICs within a second, it two packets with invalid MICs within a second, it disassociates all its clients, and stops all activity for disassociates all its clients, and stops all activity for a minutea minute

• Only two packets a minute enough to completely Only two packets a minute enough to completely stop a wireless networkstop a wireless network

AdvantagesAdvantages

• MobilityMobility• Ease of InstallationEase of Installation• FlexibilityFlexibility• CostCost• ReliabilityReliability• SecuritySecurity• Use unlicensed part of the radio spectrumUse unlicensed part of the radio spectrum• RoamingRoaming• SpeedSpeed

LimitationsLimitations

• InterferenceInterference• Degradation in performanceDegradation in performance• High power consumptionHigh power consumption• Limited rangeLimited range

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