7 wi fi technology

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WI-FI TECHNOLOGY



By.

P. Victer Paul

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The IEEE 802.11 technology standards, better known asWi-Fi technology.

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

It quickly and efficiently connect computers to internetservice providers and to LAN‟s respectively.



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

The congested air waves and lack of Federal

Communication Commission (FCC) regulationson transmission etiquette lead to the one majordownfall of wireless communications.

It uses two transmitting schemes Frequency

Hopping Spread Spectrum (FHSS) or DirectSequence Spread Spectrum (DSSS).

.



FHSS

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

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

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

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



DSSS

Direct sequence spread spectrum is the secondtype of spread spectrum signal transmissionallowed for BWA equipment by the FCC

Direct sequence spread spectrum transmittersuse power levels for transmission that are similarto narrow band transmitters.

The DSSS signal has a redundancy factor

built into the equipment.It actually transmits atleast 10 fully redundant copies of the data. Ithelps to resist interference from other signals.



DSSS has a process called de-spreadingthat helps reduce or possibly eliminateinterference

The Signal to Noise ratio is better forDSSS since the de-spreading helpsreduce the amount of noise being received

by the equipment.

The DSSS equipment has a considerableoutdoor range of 40km or approximately

24.8 miles.



The success of wireless technology ispressing technology companies toproduce more wireless “gadgets” based on

newer standards that fix some of Wi-Fi‟sshortcomings

So that WiMax enters into the wireless

industry.



WIMAX

WiMax,which stands for Worldwide Interoperabilityfor Microwave Access

“WiMax is the popular name of the (IEEE‟s)

802.16 wireless metropolitan-area networkstandard

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

WiMax uses low frequencies, in the 2 to 11 GHzrange.



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

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

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

“hot spots.”

WiMax promises to help corporations expand business, drive downcosts, increase overall

profitability, increase the quality of service, and increase the numberof users that connect to the

internet



REFERENCES

1. Captain, S. (2004). WiMax: Wireless on Steroids. PC World, Vol. 22 Issue 1. [Online].

Available: http://www.pcworld.com/reviews/article/0,aid,112467,00.asp.

2. Direct Sequence vs. Frequency Hopping (2000). [Online]. Available:

http://www.wavewireless.com/classroom/whitepapers/FHSSvDSSS.pdf

3. Fisher, K. (2004, January). WiMax Technology May Solve „Last Mile‟ Problem for High-

Speed Access. [Online]. Available:

http://www.arstechnica.com/news/posts/1074799974.html

4. Reinhardt, A. (2004, January 19). The Next Big Thing for Wireless?. Business Week Online.

[Online]. Available:

http://www.businessweek.com/magazine/content/04_03/b3866083_mz063.

5. Russell, K. (2003). WiMax. Computerworld, 37(48). [Online]. Available:

http://www.computerworld.com/mobiletopics/mobile/story/0,10801,87555,00.html

6. Stone, B. (2003, November 17). VC Inside. Newsweek. [Online]. Available: http://msnbc.msn.com/Default.aspx?id=3403581&p1=0

7. The WiMax Forum: At-a- glance (n.d.). [Online]. Available: http://www.alvarionusa.

com/runtime/materials/pdffiles/WiMAX_Leaflet.pdf



Faults in Wifi

There are several specific reasons whymaintenance in rural areas is hard.

Limited knowledge about wireless networking.

The chances of hardware failures are higher asa result of poor power quality.

Many locations with wireless nodes, especiallyrelays, are quite remote.

The wireless deployment, although connectinglo-cal nodes, may not be accessible remotely orthrough the Internet.



REQUIREMENTS FORDIAGNOSIS

Monitoring

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

complete network

Type # 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 No default gateway specified



Need to monitor status

Network status: The admins need an infrastructure thatcontinuously probes all the nodes and relays (e.g. pingtests)

Signal strength: It is possible that the antenna ismisaligned, or that some antenna cable or connector isdisconnected.

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

Local connectivity: One common problem with the

router boards is that the main ethernet port often stopsworking because of power spikes or lightening strikes onlong exposed cables carrying power (PoE)



Need to have back channels

Network misconfiguration:

A related problem occurs when there is a routingmisconfiguration or loop.

A particular node may be reachable but thereverse path may not work; thus pings fail toreturn.

Arelated problem occurs when there is a routing

misconfigu-ration or loop; a particular node maybe reachable but the reverse path may not work;thus pings fail to return.



Independent channel: We need the ability toaccess the remote nodes independently fromthe primary wireless link

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

We need an independent hardware basedmodule that reboots the system when itdoes not receive periodic heartbeats.



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

where the routing daemon dies or goes into abad state.

This might result in nodes becomingunreachable.

We need a safe fallback mechanism. In somecases we need the ability to set a timeout period

for new configurations where we want to test itwith the guarantee that the system would goback 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, andimproving the operational sustainability of the system. In this paper wehave presented a framework for designing networks with support formore accurate root cause fault diagnosis. The key ideas are buildingredundancy into hardware, software, and links for diagnosis such thatsome subsystems remain available even in the event of pri-mary linkfailure and thus can still be queried. We show our progress to this endby describing our initial architecture and describing how faults can bediagnosed 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 attackscalled DAIR,

which is short for Dense Array of Inexpensive Radios

It is useful for detecting rogue wireless

devices (e.g., access points) attached tocorporate networks, as well as for detectingDenial of Service attacks on Wi-Fi networks.



Types of Attacks

• Eavesdropping

• Man-in-the-middle attacks

• Denial of Service



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

• Different tools available on the internet

• Network sniffers, protocol analysers . . .

• Password collectors

• With the right equipment, it‟s possible to

eavesdrop traffic from few kilometers away



MITM Attack

1. Attacker spoofes adisassociate messagefrom the victim

2. The victim starts to

look for a new accesspoint, and the attackeradvertises his own APon a different channel,using the real AP‟s

MAC address3. The attacker connects

to the real AP usingvictim‟s MAC address



Denial of Service

• Attack on transmission frequecy used

• Frequency jamming

• Not very technical, but works

• Attack on MAC layer

• Spoofed deauthentication / disassociation messages

• can target one specific user

• Attacks on higher layer protocol (TCP/IP protocol)

• SYN Flooding



Wi-Fi Security

The requirements for Wi-Fi networksecurity can be broken down into twoprimary components:

• Authentication

User Authentication

Server Authentication

• Privacy



Authentication

• Keeping unauthorized users off the network

• User Authentication

• Authentication Server is used

• Username and password• Risk:

• Data (username & password) send before secure channelestablished

• Prone to passive eavesdropping by attacker• Solution

• Establishing a encrypted channel before sending usernameand password



Authentication (cont..)

• Server Authentication

• Digital Certificate is used

• Validation of digital certificate occurs

automatically within client software



Wi-Fi Security Techniques

• Service Set Identifier (SSID)

• Wired Equivalent Privacy (WEP)

• 802.1X Access Control

• Wireless Protected Access (WPA)

• IEEE 802.11i



Service Set Identifier (SSID)

• SSID is used to identify an 802.11 network

• It can be pre-configured or advertised inbeacon broadcast

• It is transmitted in clear text

• Provide very little security



Wired Equivalent Privacy (WEP)

• Provide same level of security as by wired network

• Original security solution offered by the IEEE 802.11standard

• Uses RC4 encryption with pre-shared keys and 24 bitinitialization vectors (IV)

• key schedule is generated by concatenating the sharedsecret key with a random generated 24-bit IV

• 32 bit ICV (Integrity check value)

• No. of bits in keyschedule is equal to sum of length ofthe plaintext and ICV



Wired Equivalent Privacy (WEP)(cont.)

• 64 bit preshared key-WEP

• 128 bit preshared key-WEP2

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

• Security Issue with WEP

• Short IV

• Static key• Offers very little security at all



802.1x Access Control

• Designed as a general purpose network access control mechanism

• Not Wi-Fi specific

• Authenticate each client connected to AP (for WLAN) or switch port(for Ethernet)

• Authentication is done with the RADIUS server, which ”tells” the

access point whether access to controlled ports should be allowedor not

• AP forces the user into an unauthorized state

• user send an EAP start message

• AP return an EAP message requesting the user‟s identity

• Identity send by user is then forwared to the authentication server by AP• Authentication server authenticate user and return an accept or reject

message back to the AP

• If accept message is return, the AP changes the client‟s state toauthorized and normal traffic flows



802.1x Access Control



Wireless Protected Access (WPA)

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

• User Authentication• 802.1x

• EAP

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

• 48 bit IV

• per packet key mixing function• Fixes all issues found from WEP

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

• Old hardware should be upgradeable to WPA



Wireless Protected Access(WPA)(cont.)

• WPA comes in two flavors• WPA-PSK

• use pre-shared key

• For SOHO environments• Single master key used for all users

• WPA Enterprise• For large organisation

• Most secure method• Unique keys for each user

• Separate username & password for each user



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 seestwo packets with invalid MICs within a second, it

disassociates all its clients, and stops all activity fora minute

• Only two packets a minute enough to completelystop a wireless network



802.11i

• Provides standard for WLAN security

• Authentication• 802.1x

• Data encryption• AES protocol is used

• Secure fast handoff-This allow roaming

between APs without requiring client tofully reauthenticate to every AP.

• Will require new hardware



Advantages

• Mobility

• Ease of Installation

• Flexibility

• Cost• Reliability

• Security

• Use unlicensed part of the radio spectrum

• Roaming

• Speed

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