Architecture and Techniques for Diagnosing Faults in IEEE 802.11 Infrastructure NetworksAtul Adya, Victor Bahl, Ranveer Chandra, Lili Qiu

Microsoft Research

Wireless Network WoesHow many times have you heard users say:My machine says: wireless connection unavailableWhy cant my machine authenticate?My performance on wireless really sucksIT Dept: Several hundred complaints per monthYou may have heard network admins say:I wonder if some one has sneakily installed an unauthorized access pointDo we have complete coverage in all the buildings?

Enterprise Wireless Problems

Main problems observed by IT department:Connectivity: RF HolesAuthentication: 802.1x protocol issuesPerformance: Unexplained delaysSecurity: Rogue APs

Existing ProductsProvide management/diagnostic functionsE.g., AirWave, CAs NSM, Air Defense, Air Magnet

Insufficient functionality:No support for disconnected clientsWeak root-cause analysis (raw data, mostly)Diagnosis only from the AP perspectiveSometimes need expensive sensor deployment

Our ContributionsFlexible client-based framework for detection and diagnosis of wireless faults

Client Conduit: communication for disconnected clients via nearby connected clients

Diagnostic mechanismsApproximate location of disconnected clientsRogue AP detectionPerformance problem analysis

Talk OutlineDiagnostics architecture and implementationClient Conduit: diagnosing disconnected clientsDiagnostic mechanismsLocating disconnected clientsDetecting unauthorized APsAnalyzing performance problemsSummary and Future Work

AssumptionsCan install diagnostic software on clientsAPs are typically closed platformsCan provide improved diagnosis with modified APsNearby clients available for fault diagnosisAt least 13 active clients on our floor (approx. 2500 sq. feet)Network admins maintain AP Location Database

Client-Centric ArchitectureDiagnostic AP Module (DAP)RADIUSKerberosLegacy APDisconnected ClientClientConduitAuthentication/User InfoDiagnostic Client Module (DC)DiagnosticServer (DS)

Diagnostic Architecture Properties

Exploits client-view of network (not just APs)

Supports proactive and reactive mechanisms

Scalable

Secure

Client ImplementationPrototype system on Windows

Native WiFi: Extensibility framework for 802.11 [Microsoft Networking 2003]

Daemon: most of functionality and main control flow

IM driver: limited changesPacket capture & monitoring

Native WiFi NIC

NDIS

Talk OutlineDiagnostics architecture and implementationClient Conduit: diagnosing disconnected clientsDiagnostic mechanismsLocating disconnected clientsDetecting unauthorized APsAnalyzing performance problemsSummary and Future Work

Cause of Disconnection

Lack of coverageIn an RF HoleJust outside AP rangeAuthentication issues, e.g., stale certificatesProtocol problems, e.g., no DHCP address

Can we communicate via nearby connected clients?

Communication via Nearby ClientsPossible (unsatisfactory) solutions:Multiple radios: extra radio for diagnosticsMultiNet [InfoCom04]: Multiplex Happy between Infrastructure/Adhoc modesPenalizing normal case behavior for rare scenarioConnected Client Happy (Infrastructure)Disconnected ClientGrumpyAccess PointCannot be on 2 networks. Packet dropped!SOSAdhoc Mode

Our Solution: Client Conduit Stops beaconingConnected Client HappyDisconnectedClient GrumpyAccess PointDisconnected station detected Becomes an Access Point(Starts beaconing)SOS (Beacon)SOS Ack(Probe Req)Ad hoc network via MultiNetHelp disconnected wireless clients with:Online diagnosisCertificate bootstrapping DisconnectedClient Not-so-Grumpy

Client Conduit Features

Incurs no extra overhead for connected clientsUse existing 802.11 messages: beacons & probes

Works with legacy APs

Includes security mechanisms to avoid abuses

Client Conduit PerformanceTime for Grumpy to get connected < 7 secondsReduced time can enable transparent recoveryBandwidth available for diagnosis > 400 Kbps (when Happy donates only 20% of time)

Chart1

0.174894462.183125140.13889390.118577080.3901191.836074881.86099

0.17500.1250.10.39011901.86099

6.7 seconds

2.7 seconds

Set channel

Become AP

Set SSID

Set Beacon Period

Get Ack

Become Station

Adhoc-mode association

Time (seconds)

Conduit

ORIGINAL VALUES

User time

Actionwhen finished (ms)User time (ms)Kernel time (ms)With PollUser time with polling (ms)Time (seconds)Actionwhen finished (ms)User time (ms)Kernel time (ms)With PollUser time with polling (ms)

Set channel174.89446174.89446175176.6462666667176.64626666670.174894460.175Set channel174.89446174.89446175176.6462666667176.6462666667

Become AP1358.01962183.12514998.4381106.1061929.45983333332.183125140Detect nearby client190.5097615.61530192.23315.5867333333

Sleep 1 second2358.0196100010002106.1061100010Become AP1358.01961167.50984998.4381106.1061913.8731

Set SSID2496.9135138.89391252291.3894833333185.28338333330.13889390.125Sleep 1 second2358.0196100010002106.10611000

Set Beacon Period2615.49058118.577081002397.72515106.33566666670.118577080.1Set SSID2496.9135138.89391252291.3894833333185.2833833333

Get Ack3005.60958390.119390.1198816.31566418.590450.3901190.390119Set Beacon Period2615.49058118.577081002397.72515106.3356666667

Become Station3841.684461836.07488998.4389918.381102.06441.836074880Get Ack3005.60958390.119390.1198816.31566418.59045

Sleep 1 second10001000100010Become STA3841.68446836.07488998.4389918.381102.0644

Adhoc-mode association1860.991860.991860.991.860991.86099Sleep 1 second100010001000

Adhoc-mode association1860.991860.991860.99

8702.674468.702674462.651109

No mode changes

ASSOCIATION_INFO0ms,Total=

RCHECK_ADAPTER0ms,Total=0-5

RGET_CAPTURED_PACKETS0ms,Total=0-319

RGET_GENERIC_INFOS0ms,Total=0-233

RQUERY_ADAPTER_LIST0ms,Total=0-6

RRECEIVE_UPCALL0ms,Total=0-314

R8021X_STATE31.25ms,Total=0-10

WBEACON_PERIOD100ms,Total=125-20

WCAPTURE_FILTER0ms,Total=100-5

WCURRENT_CHANNEL175ms,Total=0-15

WCURRENT_OPERATION_MODE998.438ms,Total=350-10

WDESIRED_SSID125ms,Total=1996.875-10

WDIAGNOSTIC_MSG0ms,Total=125-5

WPROMISCUOUS_MODE0ms,Total=0-5

WSET_SPECIAL_EVENT0ms,Total=0-5

W0-5

Conduit

174.894461183.125141000138.8939118.57708390.119836.0748810001860.99

175998.4381000125100390.119998.43810001860.99

176.6462666667929.45983333331000185.2833833333106.33566666676418.590451102.064410001860.99

Set channel

Become AP

Sleep 1 second

Set SSID

Set Beacon Period

Get Ack

Become STA

Sleep 1 second

Adhoc-mode association

Time (msec)

Channels

AP ChannelFor 5 scans

1123

21234

3123456

4123456

51234567

6345678

7345678910

84567891011

9567891011

10678910

117891011

AP channel (for 1 scan)

113

2123

3123456

412346

52345

645678

74678

8458911

967891011

107810

1181011

Channels

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

00000000000000

Detected in 1 and 5 sec runsDetected only in 5 sec run

Channel on which AP beacons

Channel on which beacons are decoded correctly

Motivation

000000

000000

000000

000000

000000

000000

000000

000000

000000

000000

000000

Channel on which AP beacons

Channel on which beacons are decoded correctly

Promiscuous-CPU

MonthNo. of Wireless-related problems

1675

2525

3600

4515

5515

6675

Promiscuous-CPU

0

0

0

0

0

0

Month

No. of wireless-related problems

Arch

Promiscuous modeNon-promiscuous mode

Time (secs)CPUTime (secs)CPU

0-6.1800-6.20

0.53-5.655.780.53-5.670

1.05-5.138.991.05-5.150

1.56-4.6201.56-4.640

2.08-4.18.992.08-4.120

2.59-3.595.952.59-3.610

3.11-3.072.923.11-3.090

3.62-2.5603.62-2.580

4.14-2.042.924.14-2.060

4.65-1.532.924.65-1.550

5.17-1.012.925.17-1.030

5.68-0.52.925.68-0.520

6.18006.200

6.680.506.710.510

7.21.025.957.211.010

7.711.532.927.731.530

8.212.036.148.222.020

8.712.536.148.742.540

9.223.042.929.263.060

9.743.562.929.773.570

10.254.078.9910.294.095.95

10.754.573.0210.84.60

11.275.09011.325.120

11.775.593.0211.825.620

12.276.093.0212.316.110

12.776.593.0212.816.610

13.277.096.1413.317.110

13.787.65.9513.837.630

14.38.125.9514.348.140

14.818.635.9514.868.660

15.339.15015.379.170

15.839.653.0215.899.692.92

16.3410.16016.3910.190

16.8410.666.1416.8910.693.02

17.3411.163.0217.411.28.99

17.8611.685.9517.911.70

18.3712.195.9518.412.20

18.8712.696.1418.912.79.27

19.3813.25.9519.4113.210

19.913.725.9519.9113.710

20.4114.235.9520.4314.230

20.9314.75020.9514.750

21.4515.272.9221.4615.260

21.9415.7615.5321.9615.760

22.4416.26022.4616.260

22.9416.76022.9616.760

23.4617.282.9223.4717.270

23.9717.792.9223.9717.770

24.4918.312.9224.4918.290

2518.828.992518.80

25.5219.342.9225.5219.320

26.0519.872.8326.0219.820

26.5520.373.0226.5220.320

27.0620.88027.0220.823.02

27.5821.45.9527.5221.323.02

28.0921.915.9528.0221.820

28.5922.416.1428.5322.330

29.0922.913.0229.0522.850

29.6223.44029.5623.362.92

30.1223.943.0230.0723.870

30.6224.443.0230.5924.392.92

31.1424.962.9231.0924.893.02

31.6525.47031.5925.390

32.1725.99032.0925.890

32.6826.5032.5926.390

33.227.028.9933.126.92.92

33.7127.53033.6227.420

34.2328.052.9234.1327.930

34.7428.568.9934.6328.430

35.2629.08035.1328.930

35.7729.592.9235.6329.430

36.2930.112.9236.1329.930

36.7930.619.2736.6330.430

37.2931.113.0237.1530.950

37.7831.6037.6631.460

38.332.122.9238.1831.980

38.8232.642.9238.6932.490

39.3333.152.9239.2133.010

39.8533.672.9239.7233.525.95

40.3634.185.9540.2434.040

40.8834.72.9240.7534.550

41.3935.2112.0241.2735.070

41.9135.735.9541.7735.570

42.4236.242.9242.2736.070

42.9436.768.9942.7636.563.02

43.4437.266.1443.2837.082.92

43.9537.772.9243.7937.590

44.4538.27044.3138.112.92

44.9738.798.9944.8238.620

45.4839.35.9545.3239.120

45.9839.89.2745.8439.640

46.5140.332.8346.3540.150

47.0240.842.9246.8740.670

47.5441.368.9947.3841.180

48.0641.882.9247.8841.680

48.5742.392.9248.3842.180

49.0942.912.9248.8842.680

49.643.425.9549.443.20

50.143.92049.9143.710

50.6244.4412.0250.4344.230

51.1344.952.9250.9444.740

51.6545.472.9251.4645.260

52.1445.963.0251.9745.770

52.6646.48052.4946.290

53.1646.986.145346.80

53.6647.483.0253.5247.320

54.1747.99054.0347.830

54.6948.512.9254.5348.330

55.1949.016.1455.0348.830

55.749.528.9955.5349.330

56.2250.045.9556.0349.830

56.7350.552.9256.5550.350

57.2551.075.9557.0650.860

57.7551.57057.5851.380

58.2552.07058.0951.890

58.7552.57058.6152.410

59.2553.076.1459.1252.920

59.7653.585.9559.6453.440

60.2654.086.1460.1553.950

60.7754.595.9560.6554.453.02

61.2955.11061.1554.950

61.7955.613.0261.6655.460

62.2956.113.0262.1855.980

62.7956.61062.6856.480

63.2957.11063.1856.980

63.7957.613.0263.6857.480

64.358.122.9264.1957.990

64.858.62064.7158.510

65.359.123.0265.2159.010

65.859.623.0265.7159.510

66.360.12066.2260.020

66.8160.638.9966.7260.520

67.3361.155.9567.2261.020

67.8461.668.9967.7261.523.02

68.3662.18068.2362.030

68.8862.72.9268.7562.550

69.3963.215.9569.2763.070

69.9163.73069.7863.585.95

70.4264.242.9270.2864.083.02

70.9464.76070.864.60

71.4565.27071.2965.090

71.9765.79071.7965.590

72.4866.32.9272.2966.090

72.9866.83.0272.8166.610

73.567.322.9273.3167.110

74.0167.832.9273.8267.620

74.5368.35074.3468.140

Arch

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Promiscuous mode

Normal mode

Time (secs)

CPU Usage

Location-1

Real dataNo filtered data

040733.9775390625040733.9775390625

119304.88574218751144708.3427734375

227295.5976562522457312.80859375

335226.10742187533456617.267578125

445206.61523437544456721.7275390625

556357.235351562555467926.296875

668308.045898437566467230.859375

779398.96289062577467235.421875

887279.672851562588467439.986328125

9963310.29101562599467444.55078125

11082011.091796875110467649.1171875

12172511.7998046875121467753.6845703125

13241312.203125132467758.251953125

14363012.818359375143467762.8193359375

18751013.31640625154467767.38671875

19851713.8212890625165467771.9541015625

22041314.224609375176467776.521484375

23140414.619140625187467681.087890625

24240415.013671875198467785.6552734375

25351915.5205078125209467590.220703125

26441415.9248046875220467594.7861328125

27552016.4326171875231467699.3525390625

29752616.94628906252424676103.9189453125

30851917.4531252534675108.484375

31951117.95214843752644676113.05078125

33040418.34667968752754677117.6181640625

34141418.75097656252864676122.1845703125

37341119.152343752974790126.8623046875

38452019.660156253084783131.533203125

41741420.0644531253194783136.2041015625

43962820.6777343753304782140.8740234375

45052921.19433593753414783145.544921875

48340421.58886718753514783150.2158203125

51652022.09667968753624783154.88671875

52740422.49121093753734783159.5576171875

53862823.10449218753844783164.228515625

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63641326.54199218754724975202.078125

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68052328.9082031255164974221.509765625

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92241338.5175781257245080314.4404296875

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95552039.4316406257465176324.5556640625

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97841640.55468757685177334.6669921875

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100041341.46972656257905178344.779296875

102252041.97753906258015177349.8349609375

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104452543.10253906258235178359.9482421875

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137641454.79882812510895281481.791015625

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148641656.526367187511355282502.4267578125

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157352458.0585937511685283517.90625

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184852068.5195312513985283626.2412109375

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188041369.33007812514205284636.5615234375

190241369.733398437514315284641.7216796875

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197941371.8554687514865282667.515625

199041372.258789062514975281672.6728515625

200152072.766601562515085282677.8310546875

201262673.377929687515195283682.990234375

202351973.88476562515305283688.1494140625

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205641375.512695312515625281703.625

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207873576.633789062515845281713.94140625

208941377.03710937515955281719.0986328125

211141477.4414062516065281724.255859375

213252277.95117187516175280729.412109375

214452278.460937516285281734.5693359375

215541378.864257812516395280739.7255859375

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222041379.67382812516615281750.0390625

223141380.077148437516725281755.1962890625

228641680.483398437516835281760.353515625

229762981.0976562516945283765.5126953125

230862881.710937517055282770.6708984375

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No Filters at DC

Filtered at DC

Time (seconds)

Cummulative no. of KBytes sent

Location-2

MedianMinMaxMedian -minMax - Median

No Error0007.3810028149.748229672710.525641312812.274749197512.28342272519.7482296727012.28342272519.74822967272.5351930523

E(1)103.0488.034210082510.525641312810.798075537312.274749197512.283422725110.5256413128012.283422725110.52564131281.7577814123

E(2)208.03421008259.748229672711.901763311712.274749197512.274749197512.283422725111.9017633117012.283422725111.90176331170.3816594134

E(1,2)303.0489.56899547819.611252204610.798075537311.831827397517.28654806599.6112522046017.28654806599.61125220467.6752958613

E(3)407.461146119.43545614139.74463252839.748229672710.525641312812.27474919759.7446325283012.27474919759.74463252832.5301166693

E(1,3)53.048119387.461146118.28519353669.43545614139.744632528311.938076834512.27474919759.43545614133.0481193812.27474919756.38733676132.8392930562

E(2,3)603.93256355029.748229672711.901763311712.136711647412.274749197512.283422725111.9017633117012.283422725111.90176331170.3816594134

E(1,2,3)72.81939980243.048119383.93256355027.4611461112.136711647416.93270108717.11584957667.461146112.819399802417.11584957664.64174630769.6547034666

Location-2

02.53519305239.7482296727

01.757781412310.5256413128

00.381659413411.9017633117

07.67529586139.6112522046

02.53011666939.7446325283

02.83929305626.3873367613

00.381659413411.9017633117

09.65470346664.6417463076

Median Location Error (metres)

Idletimes

MedianMinMaxMedian -minMax - Median

No Error0007.3810028149.748229672710.525641312812.274749197512.28342272519.7482296727012.28342272519.74822967272.5351930523

E(1)16.095880628.03421008259.287677220110.525641312810.798075537312.274749197517.286548065910.52564131286.0958806217.28654806594.42976069286.7609067531

E(2)2003.181230629.56899547819.748229672710.798075537317.28654806599.5689954781017.28654806599.56899547817.7175525878

E(1,2)33.181230626.095880628.78269946749.28767722019.568995478110.798075537333.53014225769.28767722013.1812306233.53014225766.106446600124.2424650375

E(3)4009.61125220469.74463252839.748229672710.525641312817.39661083639.7446325283017.39661083639.74463252837.6519783081

E(1,3)53.93256355026.096119387.461146117.800091786912.283422725117.396610836325.28484077897.80009178693.932563550225.28484077893.867528236717.484748992

E(2,3)605.71646294587.4611461111.733814059511.938076834513.423900000215.011933779711.7338140595015.011933779711.73381405953.2781197202

E(1,2,3)73.93256355026.096119387.18859282487.461146117.80009178699.435456141332.9723493457.461146113.932563550232.9723493453.528582559825.511203235

Idletimes

02.53519305239.7482296727

06.76090675314.4297606928

07.71755258789.5689954781

024.24246503756.1064466001

07.65197830819.7446325283

017.4847489923.8675282367

03.278119720211.7338140595

025.5112032353.5285825598

Median Location Error (metres)

TimeReal TimeAvg Idle PeriodAvg Max Idle PeriodTotal Idle PeriodsNum Samples

00.000099.2593223.1111279

10.083376.2286202.0000359

20.166780.8182234.7778339

30.250066.6250198.7778409

40.333347.9592171.7500498

50.4167119.3500238.6250208

60.500083.4688230.6667329

70.583357.4390207.2500418

80.666769.7632205.4444389

90.750078.3529205.3333349

100.833386.3226218.7778319

110.916799.1111237.6667279

121.000092.1724220.1111299

131.083389.1667209.3333309

141.166792.3793224.4444299

151.250064.8537207.2222419

161.333381.0303198.8889339

171.4167134.4500248.1111209

181.5000122.0909239.7778229

191.583378.5294208.5556349

201.666757.2609185.4444469

211.7500127.8571239.6667219

221.833383.6563205.6667329

231.9167103.1154220.3333269

242.0000122.0909240.4444229

252.083355.2708202.0000489

262.166766.3750231.5556409

272.250078.5294213.7778349

282.333343.1967182.4444619

292.416742.4194221.2222629

302.500092.3448222.3333299

312.583381.0909218.2222339

322.666771.5135192.7778379

332.750086.2258207.8889319

342.833379.5667179.4444309

352.916799.1667235.0000248

363.000099.2500215.3750248

373.083379.1724193.6250298

383.1667103.4348238.7500238

393.250099.3333223.3333279

403.333378.5000200.0000349

413.416772.0606183.3333339

423.5000103.6522233.1250238

433.583368.4359202.5556399

443.666771.5135199.8889379

453.750078.4118210.1111349

463.833368.2051211.1111399

473.916792.2069227.1111299

484.000095.5000227.6667289

494.083365.0000205.8889419

504.1667128.0000247.1111219

514.250086.1290214.7778319

524.333389.0667199.5556309

534.4167134.4000249.5556209

544.5000111.8333238.2222249

554.583372.1892203.4444379

564.666783.0000199.0000329

574.750092.2414234.6667299

584.833378.5000213.4444349

594.9167134.4500249.5556209

605.000086.3226228.8889319

615.083370.2105196.0000389

625.166786.2258234.1111319

635.250063.3810195.8889429

645.333355.3333179.4444489

655.4167103.1154240.5556269

665.500089.2333238.1111309

675.583354.1020204.8889499

685.666758.4889174.7778459

695.750072.0000216.2222379

705.833376.2857200.7778359

715.916786.1290246.3333319

726.0000107.2800237.7778259

736.083380.9697212.3333339

746.166789.0667230.4444309

756.250089.0333227.7778309

766.333364.8780182.4444419

776.4167107.2800231.5556259

786.500086.2258216.4444319

796.583374.1389196.4444369

806.666766.2250176.3333409

816.750086.3226221.4444319

826.833381.9310202.0000298

836.916765.5278202.1250368

847.0000104.3000235.0000207

857.083399.3333208.7143217

867.1667122.7059243.2857177

877.250079.8846208.8571267

887.333362.2727172.5714337

897.4167116.0000242.8571187

907.500063.9189208.0000378

917.583362.8485194.2857337

927.666788.8500194.1667206

937.750084.7143219.1667216

947.833381.9655180.0000298

957.9167115.9444237.7143187

968.000059.0000167.1250408

978.0833104.3000214.8571207

988.1667103.4348236.5000238

998.250074.1250202.3750328

1008.333376.6774179.7500318

1018.4167119.3500239.5000208

1028.500083.1600223.4286257

1038.583364.6563172.5714327

1048.666779.6538189.5714267

1058.750099.2857222.8571217

1068.833368.4231178.0000266

1078.916784.9524197.6667216

1089.000089.3000209.3333206

1099.083342.7317149.6667416

1109.166755.1250204.3333326

1119.250061.2069201.8333296

1129.333374.2500146.2000205

1139.416759.1000187.0000306

1149.500048.8889147.6667366

1159.583368.4615169.3333266

1169.666765.3333167.6667276

1179.750094.0000208.3333196

1189.833377.5217154.3333236

1199.916781.0000211.1667226

12010.000094.0000208.6667196

12110.083384.9524182.1667216

12210.166781.0000202.8333226

12310.250089.2500209.1667206

12410.333347.6216157.3333376

12510.416728.0000159.6667616

12610.500077.3913210.0000236

12710.583381.0455181.8333226

12810.666763.0000167.8333286

12910.750057.0645182.5000316

13010.833358.8667172.8333306

13110.916756.9677161.8333316

13211.000063.3214176.8333286

13311.083355.3438164.8333326

13411.166746.1316185.1667386

13511.250085.0000209.8333216

13611.333370.6667144.6000215

13711.416778.1053186.6000195

13811.500089.2500212.3333206

13911.583368.4231175.5000266

14011.666753.2121152.0000336

14111.750056.9032205.6667316

14211.833357.0323172.0000316

14311.916794.0000204.1667196

14412.000059.4828192.1667296

14512.083367.3636159.0000225

14612.166747.3871180.2000315

14712.250036.8205181.2000395

14812.333349.1111156.6667366

14912.416799.2667215.4000155

15012.500043.8000195.0000406

15112.583324.7206141.1667686

15212.666733.8235130.1667516

15312.750036.9787164.8333476

15412.833320.7761149.0000675

15512.916746.2895197.8333386

15613.000071.1200173.6667256

15713.083360.4828161.6667296

15813.166770.6667192.4000215

15913.250078.2105197.2000195

16013.333352.7500153.6000285

16113.416764.2609199.4000235

16213.500067.2727173.4000225

16313.583349.1250141.2500244

16413.666745.5000145.6000325

16513.750074.2500179.4000205

16613.833360.6667150.2000245

16713.916786.8235205.0000175

16814.000073.4500213.2000205

16914.083343.0000156.8000345

17014.166799.3333216.0000155

17114.250067.2273208.8000225

17214.333344.2424159.8000335

17314.416754.2963179.6000275

17414.5000106.5000202.4000145

17514.583350.6207139.0000295

17614.666777.5789162.4000195

17714.750067.2273184.0000225

17814.833393.0625183.8000165

17914.9167124.2500240.8000125

18015.0000124.4167244.2000125

18115.083352.6071143.8000285

18215.166777.9474187.6000195

18315.250074.1500166.4000205

18415.333364.1739134.0000235

18515.416799.1333204.2000155

18615.500070.5238211.4000215

18715.583370.6667181.6000215

18815.666753.0909193.5000224

18915.750099.2500213.7500124

19015.833343.3333140.0000274

19115.916747.1290188.8000315

19216.000087.4118198.6000175

19316.083363.3214165.0000286

19416.166756.9032159.0000316

19516.250040.6279163.1667436

19616.333352.0000147.1667346

19716.416777.3043186.0000236

19816.500051.9118174.5000346

19916.583351.9706135.5000346

20016.666752.9091156.1667336

20116.750065.5926195.1667276

20216.833347.5946151.3333376

20316.916747.7027159.6667376

20417.000059.1333170.1667306

20517.083334.0000143.6667516

20617.166742.7073152.6667416

20717.250052.9697196.0000336

20817.333342.5610123.3333416

20917.416759.0000181.5000306

21017.500051.7941161.0000346

21117.583343.8000164.1667406

21217.666735.0000146.5000486

21317.750052.0714167.2000285

21417.833341.7143152.6667426

21517.916755.2188185.1667326

21618.000056.7097182.8333316

21718.083336.9574143.8333476

21818.166743.0882153.0000345

21918.250042.9118140.4000345

22018.333323.8500137.0000605

22118.416732.0444142.2000455

22218.500035.6122173.5000496

22318.583332.5660146.5000536

22418.666749.6571181.0000356

22518.750035.6458154.3333486

22618.833334.0196166.6667516

22718.916720.0241128.3333836

22819.000020.3205147.6667786

22919.083318.2432118.0000745

23019.166721.7126141.2857877

23119.250029.8276132.8333586

23219.333330.4375134.2857647

23319.416733.5714160.2000425

23419.500049.8621168.8000295

23519.583352.2051156.0000397

23619.666743.5000145.1667406

23719.750057.0968163.1667316

23819.833360.6471175.4286347

23919.916764.7500198.8571327

24020.000042.5833165.0000487

24120.083337.4630159.5714547

24220.166753.6591179.7500448

24320.250062.6061192.1429337

24420.333332.5429160.3750708

24520.416743.8462186.8750528

24620.500033.6029178.3750688

24720.583337.9057122.4286537

24820.666736.4000172.0000557

24920.750041.9091185.2500558

25020.833329.7273136.6250778

25120.916733.2754169.1250698

25221.000038.0820164.7500618

25321.083336.0000169.5000648

25421.166740.7143169.3750568

25521.250035.1719154.3750648

25621.333350.3913174.3750468

25721.416735.2923193.0000658

25821.500023.8556145.6250908

25921.583325.8851135.2500878

26021.666735.9444161.0000547

26121.750036.3617173.6667476

26221.833342.5854188.5000416

26321.916751.7353198.5000346

26422.000047.1081201.3333376

26522.083361.1034186.5000296

26622.166784.7619214.5000216

26722.250047.0811183.8333376

26822.333374.2500190.6667246

26922.416760.8621200.5000296

27022.500030.7857122.5000566

27122.583350.0571216.6667356

27222.666748.4722174.6667366

27322.750052.5000204.0000285

27422.833393.0625204.4000165

27522.916774.1389215.1111369

27623.000092.1034216.8889299

27723.083363.3095182.7778429

27823.166795.6429218.1111289

27923.250071.9189194.8889379

28023.333363.2381150.7778429

28123.4167128.0000226.2222219

28223.500066.5750182.1111409

28323.583364.9512185.2222419

28423.666752.5400165.4444509

28523.750099.1481217.5556279

28623.833374.1111200.1111369

28723.9167111.7917228.5556249

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Avg Max Idle Period

Time of day (hours)

Max idle period (seconds) every 5 minutes

Talk OutlineDiagnostics architecture and implementationClient Conduit: diagnosing disconnected clientsDiagnostic mechanismsLocating disconnected clientsDetecting unauthorized APsAnalyzing performance problemsSummary and Future Work

Locating Disconnected ClientsGoal: Approximately locate to determine RF HolesSolution: Use nearby connected clients

Grumpy starts beaconingNearby clients report signal strength to serverDiagnostic server uses RADAR [InfoCom00] twiceLocates connected clientsLocates Grumpy with clients as anchor pointsLocation error: 10 15 meters

Talk OutlineDiagnostics architecture and implementationClient Conduit: diagnosing disconnected clientsDiagnostic mechanismsLocating disconnected clientsDetecting unauthorized APsAnalyzing performance problemsSummary and Future Work

Rogue AP ProblemsWhy problematic?Allow network access to unauthorized usersHurt performance: interfere with existing APs

Detection goals:Common case: mistakes by employeesDetect unauthorized IEEE 802.11 APsNot considering non-compliant APs

Solution: Use clients for monitoring nearby APs

Rogue AP DetectionClients monitor nearby APs. Send to server:MAC address, Channel, SSID, RSSI (for location)Server checks 4-tuple in AP Location DatabaseObtaining AP Information at clients:Same/overlapping channel as client: from BeaconsAP on non-overlapping channel:Active Scan periodicallyAP information from Probe Response

Rogue AP Detection Overheads

Bandwidth usage < 0.2 Kbps per client

Can active scans be performed without disruption?Sufficient idleness available (2 3 min.)Simple threshold-based prediction: Active scan completed in idle period for 95% cases

Talk OutlineDiagnostics architecture and implementationClient Conduit: diagnosing disconnected clientsDiagnostic mechanismsLocating disconnected clientsDetecting unauthorized APsAnalyzing performance problemsSummary and Future Work

SummaryDiagnostics critical for 802.11 deploymentsClient-centric architectureClient ConduitDiagnosis using nearby clientsLocate disconnected clientsDetect rogue APsAnalyze performance problemsPrototype in Windows using Native WiFiMechanisms are effective with low overheads

Future Work

Detecting Rogue Ad Hoc networks802.1x protocol analyzerDetailed wireless delay analyzerAutomated recovery after fault diagnosis