Wireless Mesh Networks: Opportunities & Challenges
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Transcript of Wireless Mesh Networks: Opportunities & Challenges
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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201
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224
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211
207
208
209
219
215
216
218
217
214
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: [email protected]: [email protected]
Mesh Networking Summit 2004Mesh Networking Summit 2004Videos, Presentations, Notes etc.Videos, Presentations, Notes etc.
http://research.microsoft.com/http://research.microsoft.com/meshsummit/meshsummit/