Wireless Mesh Networks: Wireless Mesh Networks: Opportunities & Opportunities & ChallengesChallenges

Victor BahlVictor BahlSenior ResearcherSenior ResearcherManager, Networking Research GroupManager, Networking Research GroupMicrosoft ResearchMicrosoft Research

Presentation OutlinePresentation OutlineMotivationMotivation

Viability & ChallengesViability & ChallengesNetwork Formation StudyNetwork Formation Study

Research ChallengesResearch Challenges

Some SolutionsSome SolutionsSystem Architecture and ComponentsSystem Architecture and Components

Range ManagementRange Management

Capacity Estimation & Improvement

Multi-Radio Routing

Troubleshooting Mesh NetworksTroubleshooting Mesh Networks

Testbeds & TrialsTestbeds & Trials

Conclusions Conclusions

MotivationMotivation

“Residential broadband access is an under developed technology that has the potential for profound positive effect on people’s lives and Nation’s economy”

Residential Broadband Revisited, NSFResidential Broadband Revisited, NSF Report, October 23, 2003Report, October 23, 2003

Residential Broadband Residential Broadband

Broadband as a % of total housholds

10.40%

51.70%

5.80%

19.70%

5.40%

18.20%

2.50%

8.10%

26.00%

13.40%

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

Source: Broadband & Dial-Up Access Source: Leitchman Research Group

% of housholds with BWA as F (income)

40%

29%

15%

51%

70%

0%

10%

20%

30%

40%

50%

60%

70%

80%

< $35K $35K-$50K $50K-$75K $75K-$100K > $100K

IncomeN

o O

nli

ne

Why should you care?Why should you care?The future is about rich multimedia services & The future is about rich multimedia services &

information exchangeinformation exchange ……possible only with wide-scale availability of broadband possible only with wide-scale availability of broadband

Internet accessInternet access

but…but…

Many people are still without broadband serviceMany people are still without broadband serviceMajority of the developing world does not have broadband Majority of the developing world does not have broadband connectivityconnectivity

Up to 30% (32 million homes) of a developed nation (America) Up to 30% (32 million homes) of a developed nation (America) doesn’t get broadband service (rural areas, older doesn’t get broadband service (rural areas, older neighbourhoods, poor neighbourhoods)neighbourhoods, poor neighbourhoods)

It is not economically feasible to provide wired connectivity to It is not economically feasible to provide wired connectivity to these customersthese customers

Broadband divide = Information divide = QL divideBroadband divide = Information divide = QL divide

Wiring the Last/First Mile?Wiring the Last/First Mile?

Scale & legacy make first mile expensiveScale & legacy make first mile expensive

~ 135 million housing units in the US (U.S. Census Bureau ~ 135 million housing units in the US (U.S. Census Bureau 2001)2001)• POTS (legacy) network designed for voice & built over 60 POTS (legacy) network designed for voice & built over 60

yearsyears• Cable TV networks built over last 25 yearsCable TV networks built over last 25 years

The Truck Roll Problem: The Truck Roll Problem: Touching each home incurs cost: Touching each home incurs cost: customer capital equipment; installation & servicing; central customer capital equipment; installation & servicing; central office equipment improvements; unfriendly terrain; political office equipment improvements; unfriendly terrain; political implications etc..implications etc..

In our estimate building an alternate, physical last mile replacement to hit 80% of US homes will take 19 years and cost ~ US $60-150 billion

Internet Backbone

Middle Mile Last / First Mile

Wireless First/Last Mile?Wireless First/Last Mile?< $2 Billion for 80% of the homes in US< $2 Billion for 80% of the homes in US

802.11 PHY – readily available & Inexpensive802.11 PHY – readily available & Inexpensive

Low Deployment CostLow Deployment CostDecentralized ownership & maintenance

Trivial SetupTrivial Setup

Small HardwareSmall HardwareIntegrates easily indoors & outdoorsIntegrates easily indoors & outdoors

FlexibleFlexibleDeployable In difficult terrain, both urban or remote

Option: Wireless MeshOption: Wireless Mesh

Classic Hub & Spoke NetworkMesh Network

Ad hoc multi-hop wireless networkAd hoc multi-hop wireless network

Grows “organically”Grows “organically”

Does not require any infrastructureDoes not require any infrastructure

Provides high overall capacityProvides high overall capacity

Robust & Fault tolerantRobust & Fault tolerant

No centralized management, administration No centralized management, administration necessarynecessary

Identity and security is a challengeIdentity and security is a challenge

Wireless Mesh CompaniesWireless Mesh Companies

Poletop Radio

Internet

UNIVERSITY

SkyPilot, Flarion, Motorola (Canopy) Invisible Networks, RoamAD, Vivato, Arraycomm, Malibu Networks, BeamReach Networks, NextNet Wireless, Navini Networks, etc.

Motorola (Meshnetworks Inc).,Radiant Networks, Invisible Networks, FHP, Green Packet Inc., LocustWorld, etc.

Infrastructure Based Infrastructure-less

Architecture effects design decisions onCapacity management, fairness, addressing & routing, mobility management, energy management, service levels, integration with the Internet, etc.

Top Four ScenariosTop Four Scenarios

VillageNetVillageNet – Broadband in rural areas – Broadband in rural areas

CityNet CityNet – City-wide blanket coverage– City-wide blanket coverage

CompanyNetCompanyNet - Enterprise-wide - Enterprise-wide wireless networkswireless networks

NeighborNetNeighborNet - Neighborhood - Neighborhood community networkscommunity networks

Community Mesh Community Mesh NetworksNetworks

Wireless mesh networks have the Wireless mesh networks have the potential to bridge the Broadband potential to bridge the Broadband

dividedivide

ApplicationsApplications(From a focus group study)(From a focus group study)

Inexpensive shared broadband Inexpensive shared broadband InternetInternetSharepoint Sharepoint (sharing info on goods, services, (sharing info on goods, services, A/V,..)A/V,..)

Medical & emergency responseMedical & emergency response

GamingGaming

Security - neighborhood video Security - neighborhood video surveillancesurveillance

Ubiquitous access - one “true” Ubiquitous access - one “true” networknetwork

Internet use increased social contact, public participation and size of social network. (social capital - access to people, information and resources)

Keith N. Hampton, MIT (author of “Netville Neighborhood Study”)URL: URL: http://www.asanet.org/media/neville.html

Many ChallengesMany Challenges

Business model?

Spectrum rules & etiquettes?

Connectivity? Range?

Capacity? Scale?

Security? Privacy?

Fairness? QoS?

Troubleshooting? (Self) Management? Content? Digital Rights Management (DRM)?

Mesh Viability & Mesh Viability & ChallengesChallenges

Viability Study - Mesh Viability Study - Mesh FormationFormation

Increasing range is key for good mesh connectivity

5-10% subscription rate 5-10% subscription rate needed for suburban needed for suburban topologies with topologies with documented wireless documented wireless rangesranges

Once a mesh forms, it is Once a mesh forms, it is usually well-connected usually well-connected

i.e. number of outliers are i.e. number of outliers are few (most nodes have > 2 few (most nodes have > 2 neighbors)neighbors)

Need to investigate other Need to investigate other joining modelsjoining models

Business model Business model considerations will be considerations will be importantimportant

5 GHz:5 GHz:Bandwidth is good, Bandwidth is good,

Published 802.11a Published 802.11a ranges (Yellow circles) ranges (Yellow circles) decent decent

Measured range (red Measured range (red circle) poorcircle) poor

Range is not sufficient Range is not sufficient to bootstrap mesh until to bootstrap mesh until installed % is quite high installed % is quite high (in this diagram ~50%)(in this diagram ~50%)

20

40

60

80

100

120

140

160

0

802.11a in a Multihop 802.11a in a Multihop NetworkNetworkImpact of path length on TCP Throughput

0

2000

4000

6000

8000

10000

12000

0 1 2 3 4 5 6 7

Path Length (Hops)

TC

P T

hro

ug

hp

ut

(Kb

ps)

R. Draves, J. Padhye, and B. ZillR. Draves, J. Padhye, and B. ZillComparison of Routing Metrics for Static Multi-Hop Wireless NetworksComparison of Routing Metrics for Static Multi-Hop Wireless NetworksACM SIGCOMM 2004 (also Technical Report, MSR-TR-2004-18, March 2004)ACM SIGCOMM 2004 (also Technical Report, MSR-TR-2004-18, March 2004)

Round Trip DelayRound Trip Delay

Average RTTavg_rtt = 0.1*curr_sample + 0.9*avg_rtt

One sample every 0.5 seconds

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 20 40 60 80 100 120 140 160 180

Time

Ave

rag

e R

TT

A new 100Kbps CBR connection starts every 10 seconds, between a new pair of nodes. All nodes hear each other.

Colliding CommunicationsColliding Communications

Panasonic 2.4GHz Spread Spectrum Phone 5 m and 1 wall from receiver

TCP download from a 802.11 AP

Performance worsens when there are large number of short-range radios in the vicinity

Badly written rules: Colliding standards

Phone

Victor Bahl, Amer Hassan, Pierre De Vries, Victor Bahl, Amer Hassan, Pierre De Vries, Spectrum Etiquettes for Short Range Wireless Devices Operating in the Unlicensed Band, , White paper, Spectrum White paper, Spectrum Policy: Property or Commons, Stanford Law School

To make them realTo make them realIdentify and solve key problems

build & deploy meshes in a variety of RF environments

Conclusion Conclusion Meshes are viable

existing technologies are inadequate

Problem SpaceProblem SpaceRange and CapacityRange and Capacity

Inexpensive electronically steerable directional antenna and/or Inexpensive electronically steerable directional antenna and/or MIMOMIMOMulti-frequency meshesMulti-frequency meshesMulti-radio hardware for capacity enhancement via greater Multi-radio hardware for capacity enhancement via greater spectrum utilizationspectrum utilizationData channel MAC with Interference management for higher Data channel MAC with Interference management for higher throughputthroughputRoute selection with multiple radios (channels) and link quality Route selection with multiple radios (channels) and link quality metricsmetrics

Self Healing & ManagementSelf Healing & ManagementGoal: Minimal human intervention - avoid network operator Goal: Minimal human intervention - avoid network operator Watchdog mechanism with data cleaning and liar detectionWatchdog mechanism with data cleaning and liar detectionOnline simulation based fault detection, isolation and diagnosisOnline simulation based fault detection, isolation and diagnosis

Security, Privacy, and FairnessSecurity, Privacy, and FairnessGuard against malicious users (and freeloaders)Guard against malicious users (and freeloaders)EAP-TLS (bet. MeshBoxes) , PEAPv2 or EAP-TLS (bet. clients & EAP-TLS (bet. MeshBoxes) , PEAPv2 or EAP-TLS (bet. clients & MeshBoxes)MeshBoxes)Priority based admission control, Secure traceroute Priority based admission control, Secure traceroute

Smart Spectrum UtilizationSmart Spectrum Utilization Spectrum etiquettes and/or rulesSpectrum etiquettes and/or rulesLower frequency bands (700 Mhz)Lower frequency bands (700 Mhz)Agile radios, cognitive radios, 60 GHz radio, underlay technologiesAgile radios, cognitive radios, 60 GHz radio, underlay technologiesCognitive software & applicationsCognitive software & applications

Analytical ToolsAnalytical ToolsInformation theoretic tools that predict network viability & performance Information theoretic tools that predict network viability & performance with practical constraints, based on experimental datawith practical constraints, based on experimental data

Ease of use (Plug and play, HCI)Ease of use (Plug and play, HCI)Pleasant, hassle-free user experience Pleasant, hassle-free user experience QoS protocols to improve content deliveryQoS protocols to improve content delivery

Digital Rights Management (DRM)Digital Rights Management (DRM)Broadband access popularity related to expanded digital content.Broadband access popularity related to expanded digital content.Increase the value proposition for end-users/subscribersIncrease the value proposition for end-users/subscribers

Problem Space (Cont.)Problem Space (Cont.)

Proof of concept via rapid prototyping and testbed deployments

Mesh ArchitectureMesh Architecture

End Device

Scenario: Neighborhood Wireless MeshesInternet

Gas Station

Bus Stop

Mesh Router 2

End Device (Guest to Router 1)

Mesh Router 1

Mesh End Device

EXIT

Any StreetMesh Zone

Mesh Router 3

(Internet TAP)

Mesh Router 5

Mesh Router 7

90

101

206

Mesh Router

End DeviceEnd DeviceConnectsConnects to a Mesh to a Mesh RouterRouterStandards CompliantStandards Compliant Network InterfaceNetwork Interface

Mesh Router / MeshBoxMesh Router / MeshBoxRoutes trafficRoutes traffic within the within the mesh and to the mesh and to the neighborhood Internet neighborhood Internet GatewayGatewayServes as Serves as access pointaccess point for End Devicesfor End Devices

Neighborhood Internet Neighborhood Internet GatewayGateway

GatewayGateway between the between the mesh nodes and the mesh nodes and the InternetInternet

ITAP

Key: Multiple radios, cognitive softwareKey: Multiple radios, cognitive software

ConnectivityConnectivity

Coverage @ 2.6 GHzCoverage @ 2.6 GHz

10 cell sites

Red – Good; Blue – Bad; Blue/Green Limits of Indoor coverageRed – Good; Blue – Bad; Blue/Green Limits of Indoor coverage

Coverage @ 700 MHzCoverage @ 700 MHz

3 cell sites

Red – Good; Blue – Bad; Blue/Green Limits of Indoor Red – Good; Blue – Bad; Blue/Green Limits of Indoor coveragecoverage

700 700 MHz:MHz:Much better Much better range: about 7 range: about 7 times further times further than 5 GHz at than 5 GHz at equal power equal power settingssettings

Three 2 MHz Three 2 MHz channels can channels can bootstrap a bootstrap a neighbourhood neighbourhood with ~3-5 Mbpswith ~3-5 Mbps

20

40

60

80

100

120

140

160

0

Dual Dual Freq. Freq. NetworkNetworkAs more clients come As more clients come online, links form in online, links form in high-frequency range high-frequency range and more of the mesh and more of the mesh is connected with high-is connected with high-bandwidthbandwidth

20

40

60

80

100

120

140

160

0

CapacityCapacity

Victor Bahl, Ranveer Chandra, John Dunagan, SSCH: Slotted Seeded Channel Hopping for Capacity Improvement inIEEE 802.11 Ad-Hoc Wireless Networks,ACM MobiCom 2004,Philadelphia, PA, September 2004

Capacity ImprovementCapacity Improvement

1

2

5

4 6

3

Only one of 3 pairs is active @ any given time

In current IEEE 802.11 meshes

Three ways to improve capacity

- Improve spectrum utilization

- Use multiple radios

- Use directional antennas

…..All of the above

Capacity ImprovementCapacity ImprovementProblem

Improve throughput via better utilization of the Improve throughput via better utilization of the spectrumspectrum

Design ConstraintsRequire only a single radio per nodeRequire only a single radio per nodeUse unmodified IEEE 802.11 protocolUse unmodified IEEE 802.11 protocol

Assumption Node equipped with omni-direction antenna (Node equipped with omni-direction antenna (MIMO MIMO ok)ok) Multiple orthogonal channels are availableMultiple orthogonal channels are availableChannel switching time < 80 usecs. Channel switching time < 80 usecs.

- - current speeds 150 microsecondscurrent speeds 150 microseconds

Slotted Seeded Channel Slotted Seeded Channel HoppingHoppingApproach

Divide time into slotsDivide time into slotsAt each slot, node hops to a different channel At each slot, node hops to a different channel

Senders & receiver probabilistically meet & exchange Senders & receiver probabilistically meet & exchange sch.sch.Senders loosely synchronize hopping schedule to Senders loosely synchronize hopping schedule to receivers receivers Implement as a layer 2.5 protocolImplement as a layer 2.5 protocol

FeaturesDistributed: every node makes independent choices: every node makes independent choices

Optimistic: exploits common case that nodes know : exploits common case that nodes know each others’ channel hopping scheduleseach others’ channel hopping schedules

Traffic-drivenTraffic-driven: nodes repeatedly overlap when they : nodes repeatedly overlap when they have packets to exchangehave packets to exchange

SSCHSSCH Divide time into slots: switch channels at beginning of a slot

3 channelsE.g. for 802.11bCh 1 maps to 0Ch 6 maps to 1

Ch 11 maps to 2

1 0 2 1 0 2 1 0

0 1 2 0 1 2 0 1

New Channel = (Old Channel + seed) mod (Number of Channels)seed is from 1 to (Number of Channels - 1)

Seed = 2

Seed = 1

(1 + 2) mod 3 = 0

(0 + 1) mod 3 = 1

A

B

• Enables bandwidth utilization across all channels• Does not need control channel rendezvous

SSCH: Syncing SeedsSSCH: Syncing Seeds• Each node broadcasts (channel, seed) once every slot • If B has to send packets to A, it adjusts its (channel, seed)

Stale (channel, seed) info simply results in delayed syncing

3 channels1 0 2 1 0 2 1 0

2 0 2 1 0 2 1 0

Seed

Seed

Follow A: Change next (channel, seed) to (2, 2)

A

B

2 2 2 2 2 2 2 2

1 2 2 2 2 2 2 2

2

2

1

1

B wants to start a flow with A

Capacity ImprovementCapacity Improvement

1

2

5

4 6

3

Only one of 3 pairs is active @ any given time

In current IEEE 802.11 meshes

10 msecs 10 msecs 10 msecs

1 2

3 4

1 4

5 2

Ch 1

Ch 2

…5 6 3 6Ch 3

5 4

1 6

3 2

With MSR’s SSCH enabled meshes

SSCH: PerformanceSSCH: PerformancePer-Flow throughput for disjoint flows

0

2

4

6

8

10

12

14

0 5 10 15

# Flows

Th

rou

gh

pu

t (i

n M

bp

s)

IEEE 802.11a

SSCH

SSCH significantly outperforms single channel IEEE 802.11a

Routing with Multiple Radios Routing with Multiple Radios in Wireless Meshesin Wireless Meshes

Richard Draves, Jitendra Padhye, and Brian Zill Routing in Multi-radio Multi-hop in Wireless Meshes ACM MobiCom 2004, September 2004

Atul Adya, Victor Bahl, Jitendra Padhye, Alec Wolman, and Lidong Zhou. Atul Adya, Victor Bahl, Jitendra Padhye, Alec Wolman, and Lidong Zhou. A Multi-Radio Unification Protocol for IEEE 802.11 Wireless Networks IEEE BroadNets 2004 (also Technical Report, MSR-TR-2003-41, June 2003)IEEE BroadNets 2004 (also Technical Report, MSR-TR-2003-41, June 2003)

Mesh Connectivity Layer Mesh Connectivity Layer (MCL)(MCL)Design

Multi-hop routing at layer 2.5Multi-hop routing at layer 2.5

FrameworkNDIS miniport – provides NDIS miniport – provides virtual adaptervirtual adapter on on virtual linkvirtual linkNDIS protocol – binds to physical adapters that provide next-NDIS protocol – binds to physical adapters that provide next-hop connectivityhop connectivityInserts a new L2.5 headerInserts a new L2.5 header

FeaturesWorks over heterogeneous links (e.g. wireless, powerline)Works over heterogeneous links (e.g. wireless, powerline)

Implements DSR-like routing with optimizations at Implements DSR-like routing with optimizations at virtual link virtual link layerlayer

We call itWe call it Link Quality Source Routing (LQSR)

Incorporates Link metrics: hop count, MIT’s ETX, MSR’s WCETTIncorporates Link metrics: hop count, MIT’s ETX, MSR’s WCETT

Transparent to higher layer protocols. Works equally well with Transparent to higher layer protocols. Works equally well with IPv4, IPv6, Netbeui, IPX,IPv4, IPv6, Netbeui, IPX, … …

Source & Binary DownloadAvailable @ Available @ http://research.microsoft.com/meshhttp://research.microsoft.com/mesh

Radio Selection MetricRadio Selection Metric

State-of-art metrics (shortest path, RTT, MIT’s State-of-art metrics (shortest path, RTT, MIT’s ETX) not suitable for multiple radio / nodeETX) not suitable for multiple radio / node

Do not leverage channel, range, data rate diversityDo not leverage channel, range, data rate diversity

Multi-Radio Link Quality Source Routing (MR-Multi-Radio Link Quality Source Routing (MR-LQSR)LQSR)

Link metric: Link metric: Expected Transmission Time (ETT)Takes Takes bandwidthbandwidth and and loss rateloss rate of the link into account of the link into account

Path metric: Path metric: Weighted Cumulative ETTs (WCETT)Combine link ETTs of links along the pathCombine link ETTs of links along the path

Takes Takes channel diversitychannel diversity into account into account

Incorporates into source routingIncorporates into source routing

Expected Transmission Expected Transmission TimeTimeGiven:Given:

Loss rate pBandwidth BMean packet size SMin backoff window CWmin

7i

0i

i1)(i

minbackoff

xmit

backoffxmit

p21f(p)

:Where

p)2(1

f(p)CWET

p)B(1

SET

:Where

ETETETT

Expected and Simulated Transmission timesS = 1000 Bytes, B = 1Mbps, CWmin = 320 microsec

0

0.01

0.02

0.03

0.04

0.05

0.06

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Loss Rate

Tra

ns

mis

sio

n t

ime

(s

ec

on

ds

)

Expected Transmission Time(predicted by the formula)

Transmission time observed in NSsimulation (1MB FTP transfer)

Formula matches simulations

WCETT = Combining link WCETT = Combining link ETTsETTs

Need to avoid Need to avoid unnecessarily long pathsunnecessarily long paths - bad for TCP performance- bad for TCP performance - bad for global resources- bad for global resources

All hops on a path on the All hops on a path on the same channel interferesame channel interfere

Add ETTs of hops that Add ETTs of hops that are on the same are on the same channelchannel

Path throughput is Path throughput is dominated by the dominated by the maximum of these maximum of these sumssums

Given a Given a nn hop path, where hop path, where each hop can be on any each hop can be on any one of one of kk channels, and channels, and two tuning parameters, two tuning parameters, aa and and bb::

jchannel on is hop i ij

jkj

n

ii

ETTX

whereba

Xb*ETTa*

WCETT1

1

max

Select the path with min WCETT

ResultsResultsTest Configuration

Randomly selected 100 Randomly selected 100 sender-receiver pairs (out of sender-receiver pairs (out of 23x22 = 506)23x22 = 506)2 minute TCP transfer2 minute TCP transfer

Two scenarios:Two scenarios:Baseline (Single radio): Baseline (Single radio):

802.11a NetGear cards802.11a NetGear cards

Two radiosTwo radios802.11a NetGear cards802.11a NetGear cards802.11g Proxim cards802.11g Proxim cards

Repeat forRepeat forShortest pathShortest pathMIT’s ETX metric MIT’s ETX metric MSR’s WCETT metricMSR’s WCETT metric

Median Throughput of 100 transfers

16011379

1155

2989.5

1508

844

0

500

1000

1500

2000

2500

3000

3500

WCETT ETX Shortest Path

Th

rou

gh

pu

t (K

bp

s)

Single Radio

Two Radios

WCETT utilizes 2nd radio betterthan ETX or shortest path

Troubleshooting Troubleshooting

Lili Qiu, Victor Bahl, Ananth Rao, Lidong Zhou, A Novel Framework for Troubleshooting Multihop Wireless Networks September 2003, MSR Tech Report

Network management is a process of controlling a complex data network so as to maximize its efficiency and productivity

- Network Management a Practical Perspective, Addison Wesley 1993

GoalsGoalsReactive and Pro-activeReactive and Pro-active

Investigate reported performance problems Time-series analysis to detect deviation from normal behaviorTime-series analysis to detect deviation from normal behavior

Localize and Isolate trouble spotsCollect and analyze traffic reports from mesh nodesCollect and analyze traffic reports from mesh nodes

Determine possible causes for the trouble spotsInterference, or hardware problems, or network congestion, or malicious Interference, or hardware problems, or network congestion, or malicious

nodes …. nodes ….

Respond to troubled spotsRespond to troubled spotsRe-route trafficRe-route traffic

Rate limitRate limit

Change topology via power control & directional antenna Change topology via power control & directional antenna control control

Flag environmental changes & problemsFlag environmental changes & problems

Our ApproachOur ApproachObserve, collect & clean network data from

participating nodes

Use a packet-level network simulator to detect, isolate & diagnose faults in “real-time”

Take corrective actionsTake corrective actions

Faults detected & diagnosedFaults detected & diagnosed Malicious & non-malicious Packet droppingMalicious & non-malicious Packet dropping Link congestionLink congestion External RF noiseExternal RF noise MAC misbehaviorMAC misbehavior

Fault Detection, Isolation & Diagnosis Fault Detection, Isolation & Diagnosis ProcessProcess

RootCauses

Collect DataCleanData

DiagnoseFaults

Simulate

RawData

MeasuredPerformance

Routing updates,Link Loads

Signal Strength

InjectCandidate

Faults

PerformanceEstimate

Agent Module

Manager Module

• SNMP MIBs• Performance Counters• WRAPI• MCL• Native WiFi

Steps to diagnose faultsSteps to diagnose faultsEstablish normal behaviorEstablish normal behavior

Deviation from the normal behavior indicates a potential Deviation from the normal behavior indicates a potential faultfault

Identify root causes by efficiently searching over fault Identify root causes by efficiently searching over fault space to re-produce faulty symptomsspace to re-produce faulty symptoms

Wireless Network

Simulation

Link RSS

Link Load

Routing Update

+/-

Loss rate, Throughput, Noise,…

FaultsDirectory

NETWORK

REPORTS

Expected Loss rate, Throughput, Noise,...

Error

Topology Changes

InterferenceInjection

Error

{Link, Node, Fault}

Traffic Simulation

Delay

Root Cause Analysis Root Cause Analysis ModuleModule

Troubleshooting Troubleshooting FrameworkFrameworkAdvantagesAdvantages

Flexible & customizable for a large class of networksFlexible & customizable for a large class of networks

Captures complicated interactionsCaptures complicated interactions within the network within the network between the network & environment, and between the network & environment, and among multiple faultsamong multiple faults

Extensible in its ability to detect new faultsExtensible in its ability to detect new faults

Facilitates what-if analysisFacilitates what-if analysis

ChallengesChallengesAccurately reproduce the behavior of the network inside Accurately reproduce the behavior of the network inside a simulatora simulator

Build a fault diagnosis technique using the simulator as Build a fault diagnosis technique using the simulator as a diagnosis toola diagnosis tool

Diagnosis PerformanceDiagnosis Performance

Number of faults

4 6 8 10 12 14

Coverage

11 11 0.750.75 0.70.7 0.920.92 0.860.86

False Positive

00 00 00 00 0.250.25 0.290.29

25 node random topology

Faults detected:- Random packet dropping- MAC misbehavior- External noise

Testbeds & TrialsTestbeds & Trials

TestbedsTestbedsDetails

60 (Bldg. 32) + 25 (Bldg. 112) nodes60 (Bldg. 32) + 25 (Bldg. 112) nodesInexpensive desktops (HP d530 SF)Inexpensive desktops (HP d530 SF)Two 802.11 radios in each nodeTwo 802.11 radios in each node

NetGear WAG or WAB, Proxim NetGear WAG or WAB, Proxim OriNOCOOriNOCOCards can operate in a, b or g mode.Cards can operate in a, b or g mode.

PurposeVerification of the mesh software stackVerification of the mesh software stack

Routing protocol behaviorRouting protocol behaviorFault diagnosis and mesh Fault diagnosis and mesh management algorithmsmanagement algorithmsSecurity and privacy architecture Security and privacy architecture Range and robustness @ 5 GHz with Range and robustness @ 5 GHz with different 802.11a hardwaredifferent 802.11a hardware

Stress TestingVarious methods of loading testbed:Various methods of loading testbed:

Harpoon traffic generator Harpoon traffic generator (University of (University of Wisconsin) Wisconsin)

Peer Metric traffic generator Peer Metric traffic generator Ad-hoc use by researchers Ad-hoc use by researchers

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215

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218

217

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223

Appro

x. 6

1 m

Approx. 32 m

Redmond Apartment TrialsRedmond Apartment Trials

Microsoft Campus

32 Bellaire Apts

31

UNIT FF UNIT GG

Road

UNIT HH20 Feet

ControlAptGG302

Road

Parking Lot

FF203

UNIT CC

UNIT BB

Carport

BB103

BB302

BB201

ControlAptGG302

GG202

HH301

B

B

B

B

B

B

B

B

A

A

bb

a

a

= MeshBox

A B

B

A

FF102

B

A

A

A

A

Redmond Apartment TrialRedmond Apartment Trial

Control Apt GG302 Mesh Box

Mesh Hall (Kitchen)

Apt FF201

Cambridge UK TrialCambridge UK Trial

MSR-Cambridge - 1st Floor, Mesh box Locations

UK3-GtwyUK8

UKMCE20

UK2

UK6UK1UK-MCE20 is the

Kiosk with posters.

= Mesh Box location = Mesh Box location

10 node meshWorking with ehome to create a media sharing demo in collaboration with ZCast DVB trial

Deployed by The Venice Team

Mesh Visualization ModuleMesh Visualization Module

Data Channel RadioMiniport Driver

Control Channel Radio

Miniport driver

Mesh Routing Functionality

Mesh Management Module

TCP / IP

Mesh Connectivity Layer(MCL)

Multi-hop Routing/Bridging Radio Selection Metric

Topology Control

Link Monitor Module

Mesh Box Configuration

SECURITY

Diagnostics Kernel Module

Diagnostics Client and Server DLLs

ResourcesResources

Software, Papers, Presentations, Software, Papers, Presentations, articlesarticles

URL: URL: http://research.microsoft.com/mesh/http://research.microsoft.com/mesh/

Mesh Research Academic Resource KitMesh Research Academic Resource KitContact: bahl@microsoft.comContact: bahl@microsoft.com

Mesh Networking Summit 2004Mesh Networking Summit 2004Videos, Presentations, Notes etc.Videos, Presentations, Notes etc.

http://research.microsoft.com/http://research.microsoft.com/meshsummit/meshsummit/