Wireless Fidelity(Wi-Fi)

Submitted by,

Premsingh Thangasamy.S 9911112007 I year M.Tech Network Engineering

Introduction How Wi-Fi Works? Wi-Fi Technology How to connect Wi-Fi Network? Wi-Fi Access Protocol Wi-Fi Applications Issues in Wi-Fi networks Wi-Fi Security Advantages Limitations

Agenda

IntroductionWireless Technology is an alternative to Wired Technology, which is commonly used, for connecting devices in wireless mode.

A Wi-Fi is an electronic devices, such as a personal computer, video game console, Smartphone, or digital audio player can connect to the internet via a wireless network access point.

An access point (or hotspot) has a range of about 20 meters (65 feet) indoors as few rooms and a greater range outdoors, as many square miles.

Wi-Fi access can provide at Organizations and businesses such as homes, offices, airports, hotels and restaurants often provide free-use hotspots to attract or assist clients.

There are three most important items which makes Wi-Fi working in your laptop or desktop. These are,

Radio SignalsWi-Fi Card which fits in your laptop or computer.Hotspots which create Wi-Fi Network.

How Wi-Fi works?

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

IEEE 802.11 wireless LANs provides 1- or 2-Mbps transmission in the 2.4-GHz band using either frequency-hopping spread spectrum (FHSS) or direct-sequence spread spectrum (DSSS).

The 802.11 standard is defined through several specifications of WLANs such as,

•IEEE 802.11b•IEEE 802.11a•IEEE 802.11g

Parameter 802.11a 802.11b 802.11g

Standard approved Sept 1999 Sept 1999 June 2003

Available bandwidth 300MHz 83.5MHz 83.5MHz

No. of overlapping channel

4 3 3

Frequency 5GHz 2.4GHz 2.4GHz

Typical Data Rate 23 Mbit/s 4.5 Mbit/s 19 Mbit/s

Maximum Data Rate 54 Mbit/s 11 Mbit/s 54 Mbit/s

Range 115 feet 115 feet 125 feet

Compatibility None None Backward compatible with b

Advantages

• fast maximum speed• regulated frequencies

prevent signal interference from other devices

 

• lowest cost• signal range is good and

not easily obstructed.

• fast maximum speed• signal range is good and

not easily obstructed

Dis-advantages

•  highest cost• shorter range signal that

is more easily obstructed

• slowest maximum speed• home appliances may

interfere on the unregulated frequency band

 

• costs more than 802.11b• appliances may interfere on

the unregulated signal frequency

 

802.11 standards

How to connect Wi-Fi Network?

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.

MAC Protocols:The 802.11 standards use a MAC layer known as

CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance). In CSMA/CA a Wireless node that wants to transmit & performs the following sequence:

Listen on the desired channel.If channel is idle (no active transmitters) it sends a packet.If channel is busy then, the node waits until the transmission end then a contention period where minimum time a host must transmit before it can be sure that the no other host’s packet has collided with its transmission.If the channel is still idle at the end of the contention period, then the node transmits its packet otherwise it repeats the process defined in step-3 above until it gets a free channel.

Wi-Fi Access Protocol

As Wi-Fi enabled devices have become more and more popular, wired devices are quickly becoming a thing of the past. Check out some of the new ways that Wi-Fi is being used below.

Home or office.Large Corporations & CampusesSmall Businesses or SOHO.

Wi-Fi Applications

Whole house connectivity

Public place connectivity

Wireless technology doesn’t remove any old security issues, but introduces new ones.

Hidden Terminal ProblemExposed Terminal ProblemMITM Attack(Man-in-the-middle attacks)

Issues in Wi-Fi networks

The hidden node/ terminal problem found at a point to multipoint network and it is defined as being one in which three or more nodes are present. Let there are three nodes: node A, node B and node C.

A and C cannot hear each other.A sends to B, C cannot receive A.C wants to send B, C senses a free medium.Collision occurs at B.A cannot receive the collision.A is hidden for C.

Hidden Terminal Problem

Now the Problem as follows -When B transmits to A, C detects the transmission using the carrier sense mechanism.So C defers transmitting to D.But C could have sent to D, so blocked unnecessarily.

Exposed Terminal ProblemSuppose there are four nodes: node A, node B, node

C and node D.Here,B can send to both A and C.C can send to D, but not to A or B.A and C cannot hear each other.

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

MITM Attack

There are following security mechanisms in Wi-Fi networks.such as,

Wired Equivalent Privacy (WEP)Wireless Protected Access (WPA)

Wi-Fi Security Techniques

Provide same level of security as by wired network.security as by wired network.

Uses RC4 based Uses RC4 based 40-or 104-bit 40-or 104-bit encryption with pre-shared encryption with pre-shared keys(static key) and 24 bit initialization vectors (IV).keys(static key) and 24 bit initialization vectors (IV).

Encrypt data only between 802.11 stations.once it enters the Encrypt data only between 802.11 stations.once it enters the wired side of the network (between access point) WEP is no wired side of the network (between access point) WEP is no longer valid.longer valid.

Security Issue with WEPShort IVStatic key

Offers very little security at all.

Wired Equivalent Privacy (WEP)

This is a new standard from the Wi-Fi Alliance that uses the 40 or 104-bit WEP key, but it changes the key on each packet.

That changing key functionality is called the Temporal Key Integrity Protocol (TKIP).

Uses RC4,dynamic encryption with sessionkeys and 48 bit initialization vectors (IV).

Encryption provide Protection against man-in-the-middle attacks.

Wireless Protected Access (WPA)

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

Advantages

Compatibility and Interpretability  Billing Issues Interference Mobility High power consumption Limited range Data security risks

Limitations

Wi-Fi is a universal wireless networking technology that utilizes radio frequencies to transfer data.

Wi-Fi allows for high speed Internet connections without the use of cables or wires.

It allows you to connect to the Internet from just about anywhere a coffee shop, a bed in a hotel room or a conference room at work without wires.

And the best thing of all, it's super fast almost 10 times faster than a regular dial-up connection.

Conclusion

Now the focus in wireless is shifting to the wide area.

Wi-Max, short for Worldwide Interoperability for Microwave Access, is defined in IEEE 802.16 standards is designed to deliver a metro area broadband wireless access (BWA) service.

Wi-MAX is similar wireless system to Wi-Fi, but on a much larger scale and at faster speeds.

What is Next?

Thank you