WI-FI TECHNOLOGYWI-FI TECHNOLOGY

By. By. P. Victer PaulP. Victer Paul

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The IEEE 802.11 technology standards, better known as The IEEE 802.11 technology standards, better known as Wi-Fi technology.Wi-Fi technology.

It is being deployed into Broadband Wireless Access It is being deployed into Broadband Wireless Access (BWA) equipment and Local Area Network (LAN) access (BWA) equipment and Local Area Network (LAN) access points.points.

It quickly and efficiently connect computers to internet It quickly and efficiently connect computers to internet service providers and to LAN’s respectively.service providers and to LAN’s respectively.

Wireless communication has a few problems Wireless communication has a few problems such as data rate, distance and reliability.such as data rate, distance and reliability.

The congested air waves and lack of Federal The congested air waves and lack of Federal Communication Commission (FCC) regulations Communication Commission (FCC) regulations on transmission etiquette lead to the one major on transmission etiquette lead to the one major downfall of wireless communications.downfall of wireless communications.

It uses two transmitting schemes Frequency It uses two transmitting schemes Frequency Hopping Spread Spectrum (FHSS) or Direct Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS).Sequence Spread Spectrum (DSSS).

..

FHSSFHSS

“ “The FHSS carrier will hop on predetermined,pseudo The FHSS carrier will hop on predetermined,pseudo random pattern defined using a pool of 1 MHz sub-random pattern defined using a pool of 1 MHz sub-channels defined across the entire band. channels defined across the entire band.

The FCC requires the band to be divided into at least 75 The FCC requires the band to be divided into at least 75 sub-channelssub-channels

The hopping ability creates additional security for FHSS. The hopping ability creates additional security for FHSS. It is very difficult for any unauthorized retrieval of the It is very difficult for any unauthorized retrieval of the data. data.

FHSS stays on a certain band in the frequency for a FHSS stays on a certain band in the frequency for a maximum of 400 microsecondsmaximum of 400 microseconds

DSSSDSSS

Direct sequence spread spectrum is the second Direct sequence spread spectrum is the second type of spread spectrum signal transmission type of spread spectrum signal transmission allowed for BWA equipment by the FCCallowed for BWA equipment by the FCC

Direct sequence spread spectrum transmitters Direct sequence spread spectrum transmitters use power levels for transmission that are similar use power levels for transmission that are similar to narrow band transmitters.to narrow band transmitters.

The DSSS signal has a redundancy factorThe DSSS signal has a redundancy factor built into the equipment.It actually transmits at built into the equipment.It actually transmits at

least 10 fully redundant copies of the data. It least 10 fully redundant copies of the data. It helps to resist interference from other signals.helps to resist interference from other signals.

DSSS has a process called de-spreading that DSSS has a process called de-spreading that helps reduce or possibly eliminate interferencehelps reduce or possibly eliminate interference

The Signal to Noise ratio is better for DSSS since The Signal to Noise ratio is better for DSSS since the de-spreading helps reduce the amount of the de-spreading helps reduce the amount of noise being received by the equipment. noise being received by the equipment.

The DSSS equipment has a considerable outdoor The DSSS equipment has a considerable outdoor range of 40km or approximately 24.8 miles.range of 40km or approximately 24.8 miles.

Also, the DSSS systems can send 1500 or 2400 Also, the DSSS systems can send 1500 or 2400 bytes of databytes of data

The success of wireless technology is The success of wireless technology is pressing technology companies to pressing technology companies to produce more wireless “gadgets” based on produce more wireless “gadgets” based on newer standards that fix some of Wi-Fi’s newer standards that fix some of Wi-Fi’s shortcomingsshortcomings

So that WiMax enters into the wireless So that WiMax enters into the wireless industry.industry.

WIMAXWIMAX

WiMax,which stands for Worldwide Interoperability WiMax,which stands for Worldwide Interoperability for Microwave Accessfor Microwave Access

““WiMax is the popular name of the (IEEE’s) WiMax is the popular name of the (IEEE’s) 802.16 wireless metropolitan-area network 802.16 wireless metropolitan-area network standardstandard

WiMax can span distances of up to 31 miles, WiMax can span distances of up to 31 miles, non line of sightnon line of sight

WiMax uses low frequencies, in the 2 to 11 GHz WiMax uses low frequencies, in the 2 to 11 GHz range.range.

Wi-Fi and WiMax technologies are being deployed by Internet Wi-Fi and WiMax technologies are being deployed by Internet Service Providers is to help minimize costsService Providers is to help minimize costs

The 802.16e standard that is being developed has been predicted to The 802.16e standard that is being developed has been predicted to allow users to travel at speeds of up to 60 miles per hour and still allow users to travel at speeds of up to 60 miles per hour and still maintain a steady reliable connectionmaintain a steady reliable connection

This could decrease the number of future Wi-Fi “hot spots” and This could decrease the number of future Wi-Fi “hot spots” and allow the WiMax 802.16e standard to replace them with WiMaxallow the WiMax 802.16e standard to replace them with WiMax

““hot spots.”hot spots.” WiMax promises to help corporations expand business, drive down WiMax promises to help corporations expand business, drive down

costs, increase overallcosts, increase overall profitability, increase the quality of service, and increase the number profitability, increase the quality of service, and increase the number

of users that connect to theof users that connect to the internetinternet

REFERENCESREFERENCES

1. Captain, S. (2004). WiMax: Wireless on Steroids. 1. Captain, S. (2004). WiMax: Wireless on Steroids. PC World, Vol. 22 Issue 1. [Online].PC World, Vol. 22 Issue 1. [Online]. Available: http://www.pcworld.com/reviews/article/0,aid,112467,00.asp.Available: http://www.pcworld.com/reviews/article/0,aid,112467,00.asp. 2. Direct Sequence vs. Frequency Hopping (2000). [Online]. Available:2. Direct Sequence vs. Frequency Hopping (2000). [Online]. Available: http://www.wavewireless.com/classroom/whitepapers/FHSSvDSSS.pdfhttp://www.wavewireless.com/classroom/whitepapers/FHSSvDSSS.pdf 3. Fisher, K. (2004, January). WiMax Technology May Solve ‘Last Mile’ Problem for High-3. Fisher, K. (2004, January). WiMax Technology May Solve ‘Last Mile’ Problem for High- Speed Access. [Online]. Available:Speed Access. [Online]. Available: http://www.arstechnica.com/news/posts/1074799974.htmlhttp://www.arstechnica.com/news/posts/1074799974.html 4. Reinhardt, A. (2004, January 19). The Next Big Thing for Wireless?. 4. Reinhardt, A. (2004, January 19). The Next Big Thing for Wireless?. Business Week Online.Business Week Online. [Online]. Available:[Online]. Available: http://www.businessweek.com/magazine/content/04_03/b3866083_mz063.http://www.businessweek.com/magazine/content/04_03/b3866083_mz063. 5. Russell, K. (2003). WiMax. 5. Russell, K. (2003). WiMax. Computerworld, 37(48). [Online]. Available:Computerworld, 37(48). [Online]. Available: http://www.computerworld.com/mobiletopics/mobile/story/0,10801,87555,00.htmlhttp://www.computerworld.com/mobiletopics/mobile/story/0,10801,87555,00.html 6. Stone, B. (2003, November 17). VC Inside. 6. Stone, B. (2003, November 17). VC Inside. Newsweek. [Online]. Available:Newsweek. [Online]. Available: http://msnbc.msn.com/Default.aspx?id=3403581&p1=0http://msnbc.msn.com/Default.aspx?id=3403581&p1=0 7. The WiMax Forum: At-a- glance (n.d.). [Online]. Available: http://www.alvarionusa.7. The WiMax Forum: At-a- glance (n.d.). [Online]. Available: http://www.alvarionusa. com/runtime/materials/pdffiles/WiMAX_Leaflet.pdfcom/runtime/materials/pdffiles/WiMAX_Leaflet.pdf

Faults in WifiFaults in Wifi

There are several specific reasons why maintenance in rural areas is hard.

Limited knowledge about wireless networking. The chances of hardware failures are higher as

a result of poor power quality. Many locations with wireless nodes, especially

relays, are quite remote. The wireless deployment, although connecting

lo-cal nodes, may not be accessible remotely or through the Internet.

REQUIREMENTS FOR DIAGNOSIS

Monitoring It’s hard to log in to individual routers to collect monitoring data because the

complete networkType # Description

HW 63

7

213

1

1

Router board not powered on (grid outage,

battery dead)

Router powered but wedged (low voltage,

corrupt CF cards)

Router powered but not connected to re-

mote LAN (loose ethernet cables, burnt

ethernet ports)

Router on, but wireless cards not transmit-

ting due to low supplied voltage

Router on, but pigtails not connected or

other RF connectors gone bad

Router on, but antenna misaligned

SW 4

3

2

2

No default gateway specified

Wrong ESSID, channel, mode

Wrong IP address

Misconfigured routing

Driver errors, wireless cards not recognized

Need to monitor status

Network status: The admins need an infrastructure that continuously probes all the nodes and relays (e.g. ping tests)

Signal strength: It is possible that the antenna is misaligned, or that some antenna cable or connector is disconnected.

It is possible that the antenna is misaligned, or that some antenna cable or connector is disconnected.

Local connectivity: One common problem with the

router boards is that the main ethernet port often stops working because of power spikes or lightening strikes on long exposed cables carrying power (PoE)

Need to have back channels

Network misconfiguration: A related problem occurs when there is a routing

misconfiguration or loop. A particular node may be reachable but the

reverse path may not work; thus pings fail to return.

Arelated problem occurs when there is a routing misconfigu-ration or loop; a particular node may be reachable but the reverse path may not work; thus pings fail to return.

Independent channel: We need the ability to access the remote nodes independently from the primary wireless link

Need for separate hardware control:Hard reboots: A link might be down because the board might have reached a state where it needs to be rebooted

We need an independent hardware based module that reboots the system when it does not receive periodic heartbeats.

Need for independent software services Software watchdog:We have seen problems

where the routing daemon dies or goes into a bad state.

This might result in nodes becoming unreachable.

We need a safe fallback mechanism. In some cases we need the ability to set a timeout period for new configurations where we want to test it with the guarantee that the system would go back to a safe state after the specified timeout.

CONCLUSION

Simplification of diagnosis for rural WiFi networks is an important step in empowering rural administrators, building local capacity, and improving the operational sustainability of the system. In this paper we have presented a framework for designing networks with support for more accurate root cause fault diagnosis. The key ideas are building redundancy into hardware, software, and links for diagnosis such thatsome subsystems remain available even in the event of pri-mary link failure and thus can still be queried. We show our progress to this end by describing our initial architecture and describing how faults can be diagnosed in this framework.

REFERENCES [1] Ashwini: Association for Health Welfare in the Nilgiris. http://www.ashwini.org. [2] Atheros. MadWiFi driver for Atheros Chipsets. http://sourceforge.net/projects/madwifi/. [3] K. Chebrolu, B. Raman, and S. Sen. Long-Distance 802.11b Links: Performance Measurements and Experience. In ACM MOBICOM, 2006. [4] CRCNet: Connecting Rural Communities Using WiFi. http://www.crc.net.nz. [5] M. Demmer, E. Brewer, K. Fall, S. Jain, M. Ho, and R. Patra. Implementing Delay Tolerant Networking. Intel Research Berkeley Technical Report IRB-TR-04-020, 2004. [6] Digital Gangetic Plains. http://www.iitk.ac.in/mladgp/.

ATTACKS ON WI-FI NETWORKS

The framework to monitor various attacks called DAIR,

which is short for Dense Array of Inexpensive Radios

It is useful for detecting rogue wireless

devices (e.g., access points) attached to corporate networks, as well as for detecting Denial of Service attacks on Wi-Fi networks.

Types of Attacks

• EavesdroppingEavesdropping• Man-in-the-middle attacksMan-in-the-middle attacks• Denial of ServiceDenial of Service

EavesdroppingEavesdropping

• Easy to perform, almost impossible to detectEasy to perform, almost impossible to detect• By default, everything is transmitted in clear textBy default, everything is transmitted in clear text

• Usernames, passwords, content ...Usernames, passwords, content ...• No security offered by the transmission mediumNo security offered by the transmission medium

• Different tools available on the internetDifferent tools available on the internet• Network sniffers, protocol analysers . . .Network sniffers, protocol analysers . . .• Password collectorsPassword collectors

• With the right equipment, it’s possible to With the right equipment, it’s possible to eavesdrop traffic from few kilometers awayeavesdrop traffic from few kilometers away

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

• Attack on MAC layerAttack on MAC layer• Spoofed deauthentication / disassociation messagesSpoofed deauthentication / disassociation messages• can target one specific usercan target one specific user

• Attacks on higher layer protocol (TCP/IP protocol)Attacks on higher layer protocol (TCP/IP protocol)• SYN FloodingSYN Flooding

Wi-Fi Security Wi-Fi Security

The requirements for Wi-Fi network The requirements for Wi-Fi network security can be broken down into two security can be broken down into two primary components:primary components:

• AuthenticationAuthentication User AuthenticationUser Authentication Server AuthenticationServer Authentication

• PrivacyPrivacy

AuthenticationAuthentication

• Keeping unauthorized users off the networkKeeping unauthorized users off the network• User AuthenticationUser Authentication

• Authentication Server is usedAuthentication Server is used• Username and password Username and password • Risk: Risk:

• Data (username & password) send before secure channel Data (username & password) send before secure channel establishedestablished

• Prone to passive eavesdropping by attackerProne to passive eavesdropping by attacker

• SolutionSolution• Establishing a encrypted channel before sending username Establishing a encrypted channel before sending username

and passwordand password

Authentication (cont..)Authentication (cont..)

• Server AuthenticationServer Authentication• Digital Certificate is usedDigital Certificate is used• Validation of digital certificate occurs Validation of digital certificate occurs

automatically within client softwareautomatically within client software

Wi-Fi Security TechniquesWi-Fi Security Techniques

• Service Set Identifier (SSID)Service Set Identifier (SSID)

• Wired Equivalent Privacy (WEP)Wired Equivalent Privacy (WEP)

• 802.1X Access Control802.1X Access Control

• Wireless Protected Access (WPA)Wireless Protected Access (WPA)

• IEEE 802.11iIEEE 802.11i

Service Set Identifier (SSID)Service Set Identifier (SSID)

• SSID is used to identify an 802.11 networkSSID is used to identify an 802.11 network• It can be pre-configured or advertised in It can be pre-configured or advertised in

beacon broadcastbeacon broadcast• It is transmitted in clear textIt is transmitted in clear text

• Provide very little securityProvide very little security

Wired Equivalent Privacy (WEP)Wired Equivalent Privacy (WEP)

• Provide same level of security as by wired networkProvide same level of security as by wired network• Original security solution offered by the IEEE 802.11 Original security solution offered by the IEEE 802.11

standardstandard• Uses RC4 encryption with pre-shared keys and 24 bit Uses RC4 encryption with pre-shared keys and 24 bit

initialization vectors (IV)initialization vectors (IV)• key schedule is generated by concatenating the shared key schedule is generated by concatenating the shared

secret key with a random generated 24-bit IVsecret key with a random generated 24-bit IV• 32 bit ICV (Integrity check value)32 bit ICV (Integrity check value)• No. of bits in keyschedule is equal to sum of length of No. of bits in keyschedule is equal to sum of length of

the plaintext and ICVthe plaintext and ICV

Wired Equivalent Privacy (WEP) Wired Equivalent Privacy (WEP) (cont.)(cont.)

• 64 bit preshared key-WEP64 bit preshared key-WEP• 128 bit preshared key-WEP2128 bit preshared key-WEP2• Encrypt data only between 802.11 stations.once it enters Encrypt data only between 802.11 stations.once it enters

the wired side of the network (between access point) the wired side of the network (between access point) WEP is no longer validWEP is no longer valid

• Security Issue with WEPSecurity Issue with WEP• Short IVShort IV• Static keyStatic key

• Offers very little security at allOffers very little security at all

802.1x Access Control802.1x Access Control• Designed as a general purpose network access control mechanismDesigned as a general purpose network access control mechanism

• Not Wi-Fi specificNot Wi-Fi specific• Authenticate each client connected to AP (for WLAN) or switch port Authenticate each client connected to AP (for WLAN) or switch port

(for Ethernet) (for Ethernet) • Authentication is done with the RADIUS server, which ”tells” the Authentication is done with the RADIUS server, which ”tells” the

access point whether access to controlled ports should be allowed access point whether access to controlled ports should be allowed or notor not

• AP forces the user into an unauthorized state AP forces the user into an unauthorized state • user send an EAP start messageuser send an EAP start message• AP return an EAP message requesting the user’s identityAP return an EAP message requesting the user’s identity• Identity send by user is then forwared to the authentication server by APIdentity send by user is then forwared to the authentication server by AP• Authentication server authenticate user and return an accept or reject Authentication server authenticate user and return an accept or reject

message back to the APmessage back to the AP• If accept message is return, the AP changes the client’s state to If accept message is return, the AP changes the client’s state to

authorized and normal traffic flowsauthorized and normal traffic flows

802.1x Access Control802.1x Access Control

Wireless Protected Access (WPA)Wireless Protected Access (WPA)

• WPA WPA is a specification of standard based, interoperable security is a specification of standard based, interoperable security enhancements that strongly increase the level of data protection and enhancements that strongly increase the level of data protection and access control for existing and future wireless LAN system.access control for existing and future wireless LAN system.

• User AuthenticationUser Authentication• 802.1x 802.1x • EAPEAP

• TKIP (Temporal Key Integrity Protocol) encryptionTKIP (Temporal Key Integrity Protocol) encryption• RC4, dynamic encryption keys (session based)RC4, dynamic encryption keys (session based)

• 48 bit IV48 bit IV• per packet key mixing functionper packet key mixing function

• Fixes all issues found from WEPFixes all issues found from WEP

• Uses Message Integrity Code (MIC) MichaelUses Message Integrity Code (MIC) Michael• Ensures data integrityEnsures data integrity

• Old hardware should be upgradeable to WPAOld hardware should be upgradeable to WPA

Wireless Protected Access (WPA)Wireless Protected Access (WPA)(cont.)(cont.)

• WPA comes in two flavorsWPA comes in two flavors• WPA-PSK WPA-PSK

• use pre-shared keyuse pre-shared key• For SOHO environmentsFor SOHO environments• Single master key used for all usersSingle master key used for all users

• WPA EnterpriseWPA Enterprise• For large organisationFor large organisation• Most secure methodMost secure method• Unique keys for each userUnique keys for each user• Separate username & password for each userSeparate username & password for each 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

802.11i802.11i

• Provides standard for WLAN securityProvides standard for WLAN security• AuthenticationAuthentication

• 802.1x802.1x• Data encryptionData encryption

• AES protocol is usedAES protocol is used• Secure fast handoff-This allow roaming Secure fast handoff-This allow roaming

between APs without requiring client to between APs without requiring client to fully reauthenticate to every AP.fully reauthenticate to every AP.

• Will require new hardwareWill require new hardware

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