Mesh Project Overview

8/10/2019 Mesh Project Overview

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Wireless Mesh Networks:Opportunities & Challenges

Victor Bahl

Senior ResearcherManager, Networking Research GroupMicrosoft Research


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Presentation Outline

MotivationViability & Challenges

Network Formation Study

Research Challenges

Some SolutionsSystem Architecture and Components

Range Management

Capacity Estimation & Improvement

Multi-Radio Routing

Troubleshooting Mesh Networks

Testbeds & Trials

Conclusions


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Motivation

Residential broadband access is an under developed

technology that has the potential for profound positive

effect on peoples lives and Nations economy

Residential Broadband Revisited, NSFReport, October 23, 2003


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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%

USA

South

Korea

Japan

Canada

Germany

Taiwan

France

Netherlands

Hon

gKong

S

weden

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 > $100KIncome

NoOnline


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

exchangepossible only with wide-scale availability of broadband Internet access

but

Many people are still without broadband service

Majority of the developing world does not have broadband connectivity

Up to 30% (32 million homes) of a developed nation (America) doesntget broadband service (rural areas, older neighbourhoods, poorneighbourhoods)

It is not economically feasible to provide wired connectivity to thesecustomers

Broadband divide = Information divide = QL divide


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Wiring the Last/First Mile?

Scale & legacy make first mile expensive

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

Cable TV networks built over last 25 years

The Truck Roll Problem: Touching each home incurs cost: customer

capital equipment; installation & servicing; central office equipmentimprovements; unfriendly terrain; political implications etc..

In our estimate building an alternate, physical last mile replacement to hit80% of US homes will take 19 years and cost ~ US $60-150 billion

Internet Backbone Middle Mile Last / First Mile


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Option: Wireless Mesh

Classic Hub & Spoke NetworkMesh Network

Ad hoc multi-hop wireless network

Grows organicallyDoes not require any infrastructure

Provides high overall capacity

Robust & Fault tolerant

No centralized management, administration necessary

Identity and security is a challenge


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Wireless Mesh Companies

Poletop Radio

Internet

UNIVERSITY

SkyPilot, Flarion, Motorola (Canopy)Invisible Networks, RoamAD, Vivato,

Arraycomm, Malibu Networks,BeamReach Networks, NextNetWireless, 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, mobilitymanagement, energy management, service levels, integration with the

Internet, etc.


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Top Four Scenarios

VillageNetBroadband in rural areas

CityNetCity-wide blanket coverage

CompanyNet- Enterprise-wide wireless

networks

NeighborNet- Neighborhood community

networks


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Community Mesh Networks

Wireless mesh networks have the potential

to bridge the Broadband divide


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Applications(From a focus group study)

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

Medical & emergency response

Gaming

Security - neighborhood video surveillance

Ubiquitous access - one true network

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: http://www.asanet.org/media/neville.html
http://www.asanet.org/media/neville.htmlhttp://www.asanet.org/media/neville.html


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Many Challenges

Business model?Spectrum rules & etiquettes?

Connectivity? Range?

Capacity? Scale?

Security? Privacy?

Fairness? QoS?

Troubleshooting? (Self) Management?

Content? Digital Rights Management (DRM)?


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Viability Study - Mesh Formation

Increasing range is key for good mesh connectivity

5-10% subscription rate

needed for suburbantopologies with documentedwireless ranges

Once a mesh forms, it is

usually well-connectedi.e. number of outliers are few(most nodes have > 2 neighbors)

Need to investigate otherjoining models

Business modelconsiderations will beimportant


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5 GHz:Bandwidth is good,

Published 802.11a ranges(Yellow circles) decent

Measured range (redcircle) poor

Range is not sufficient tobootstrap mesh untilinstalled % is quite high (inthis diagram ~50%)

20 40 60 80 100 120 140 1600


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

0

2000

4000

6000

8000

10000

12000

0 1 2 3 4 5 6 7

Path Length (Hops)

TCPThrough

put(Kbps)

R. Draves, J. Padhye, and B. Zill

Comparison of Routing Metrics for Static Multi-Hop Wireless Networks

ACM SIGCOMM 2004 (also Technical Report, MSR-TR-2004-18, March 2004)


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Round Trip Delay

Average RTT

avg_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

AverageRTT

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


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Colliding Communications

Panasonic 2.4GHz Spread SpectrumPhone 5 m and 1 wall from receiver

TCP download from a 802.11 AP

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

Badly written rules: Colliding standards

Phone

Victor Bahl, Amer Hassan, Pierre De Vries, Spectrum Etiquettes for Short Range

Wireless Devices Operating in the Unlicensed Band, White paper, SpectrumPolicy: Property or Commons, Stanford Law School


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To make them realIdentify and solve key problems

build & deploy meshesin a variety of RF environments

ConclusionMeshes are viableexisting technologies are inadequate

P bl S


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Problem SpaceRange and Capacity

Inexpensive electronically steerable directional antenna and/or MIMO

Multi-frequency meshesMulti-radio hardware for capacity enhancement via greater spectrumutilizationData channel MAC with Interference management for higher throughputRoute selection with multiple radios (channels) and link quality metrics

Self Healing & ManagementGoal: Minimal human intervention - avoid network operatorWatchdog mechanism with data cleaning and liar detectionOnline simulation based fault detection, isolation and diagnosis

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


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Smart Spectrum Utilization

Spectrum etiquettes and/or rules

Lower frequency bands (700 Mhz)

Agile radios, cognitive radios, 60 GHz radio, underlay technologies

Cognitive software & applications

Analytical Tools

Information theoretic tools that predict network viability & performance withpractical constraints, based on experimental data

Ease of use (Plug and play, HCI)

Pleasant, hassle-free user experience

QoS protocols to improve content delivery

Digital Rights Management (DRM)

Broadband access popularity related to expanded digital content.

Increase the value proposition for end-users/subscribers

Problem Space (Cont.)

Proof of concept via rapid prototyping and testbed deployments


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End Device

Scenario: Neighborhood Wireless Meshes

Internet

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 Device

Connects to a Mesh Router

Standards CompliantNetwork Interface

Mesh Router / MeshBoxRoutes traffic within themesh and to theneighborhood InternetGateway

Serves as access point forEnd Devices

Neighborhood Internet Gateway

Gateway between the meshnodes and the Internet

ITAP

Key: Multiple radios, cognitive software


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Connectivity


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Coverage @ 2.6 GHz

10 cell sites

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


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Coverage @ 700 MHz

3 cell sites

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


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700 MHz:Much better range:about 7 timesfurther than 5 GHz

at equal powersettings

Three 2 MHzchannels canbootstrap aneighbourhood

with ~3-5 Mbps

20 40 60 80 100 120 140 1600


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Capacity

Victor Bahl, Ranveer Chandra, John Dunagan,SSCH: Slot ted Seeded Channel Hopp ing fo r Capacity Imp rovement in

IEEE 802.11 Ad -Hoc Wireless Netwo rks,

ACM MobiCom 2004,Philadelphia, PA, September 2004


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Capacity 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


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Capacity ImprovementProblem

Improve throughput via better utilization of the spectrum

Design Constraints

Require only a single radio per nodeUse unmodified IEEE 802.11 protocol

Assumption

Node equipped with omni-direction antenna (MIMO ok)Multiple orthogonal channels are available

Channel switching time < 80 usecs.

- current speeds 150 microseconds


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Slotted Seeded Channel HoppingApproach

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

Senders & receiver probabilistically meet & exchange sch.

Senders loosely synchronize hopping schedule to receivers

Implement as a layer 2.5 protocol

FeaturesDistributed: every node makes independent choices

Optimistic: exploits common case that nodes know eachothers channel hopping schedules

Traffic-driven: nodes repeatedly overlap when they havepackets to exchange


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SSCH

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

3 channels

E.g. for 802.11b

Ch 1maps to 0

Ch 6maps to 1

Ch 11maps 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

Enables bandwidth utilization across all channelsDoes not need control channel rendezvous


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SSCH: Syncing Seeds

Each node broadcasts (channel, seed)once every slotIf 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)

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


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Capacity 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 MSRs SSCH enabled meshes


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SSCH: Performance

Per-Flow throughput for disjoint flows

0

2

4

6

8

10

12

14

0 5 10 15

# Flows

T

hroughput

(inMbps)

IEEE 802.11a

SSCH

SSCH significantly outperformssingle channel IEEE 802.11a


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Routing with Multiple Radios inWireless Meshes

Richard Draves, Jitendra Padhye, and Brian Zill

Routin g in Mult i - radio Mult i -hopin Wireless MeshesACM MobiCom 2004, September 2004

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

M h C ti it L (MCL)


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Mesh Connectivity Layer (MCL)Design

Multi-hop routing at layer 2.5

Framework

NDIS miniportprovides virtual adapter on virtual link

NDIS protocolbinds to physical adapters that provide next-hopconnectivity

Inserts a new L2.5 header

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

Implements DSR-like routing with optimizations at virtual link layerWe call itLink Quality Source Routing (LQSR)

Incorporates Link metrics: hop count, MITs ETX, MSRs WCETT

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

Source & Binary Download

Available @ http://research.microsoft.com/mesh

R di S l ti M t i
http://research.microsoft.com/meshhttp://research.microsoft.com/mesh


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Radio Selection Metric

State-of-art metrics (shortest path, RTT, MITs ETX) notsuitable for multiple radio / nodeDo not leverage channel, range, data rate diversity

Multi-Radio Link Quality Source Routing (MR-LQSR)Link metric: Expected Transmission Time (ETT)

Takes bandwidth and loss rate of the link into account

Path metric: Weighted Cumulative ETTs (WCETT)

Combine link ETTs of links along the pathTakes channel diversity into account

Incorporates into source routing


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Expected Transmission TimeGiven:

Loss ratepBandwidth B

Mean packet size S

Min backoff window CWmin

7i

0i

i1)(i

minbackoff

xmit

backoffxmit

p21f(p)

:Where

p)2(1

f(p)CWET

p)B(1

SET

:WhereETETETT

Expected and Simulated Transmission times

S = 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

Transmissiontime(seconds)

Expected Transmission Time(predicted by the formula)

Transmission time observed in NSsimulation (1MB FTP transfer)

Formula matches simulations

WCETT = Combining link ETTs


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WCETT = Combining link ETTs

Need to avoid unnecessarilylong paths

- bad for TCP performance

- bad for global resources

All hops on a path on thesame channel interfere

Add ETTs of hops that areon the same channel

Path throughput isdominated by themaximum of these sums

Given a nhop path, whereeach hop can be on any oneof kchannels, and two tuningparameters, aand b:

jchannelonishop i

ij

jkj

n

ii

ETTX

where

ba

Xb*ETTa*WCETT

1

1max

Select the path withmin WCETT


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ResultsTest Configuration

Randomly selected 100 sender-receiver pairs (out of 23x22 =506)

2 minute TCP transfer

Two scenarios:

Baseline (Single radio):802.11a NetGear cards

Two radios

802.11a NetGear cards802.11g Proxim cards

Repeat for

Shortest path

MITs ETX metric

MSRs 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

Throughput(Kbps)

Single Radio

Two Radios

WCETT utilizes 2ndradio better

than ETX or shortest path


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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


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GoalsReactive and Pro-active

Investigate reported performance problemsTime-series analysis to detect deviation from normal behavior

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

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

nodes .

Respond to troubled spotsRe-route traffic

Rate limit

Change topology via power control & directional antenna control

Flag environmental changes & problems

O A h


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Our Approach

Observe, collect & clean network data from participatingnodes

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

Take corrective actions

Faults detected & diagnosed Malicious & non-malicious Packet dropping

Link congestion

External RF noise

MAC misbehavior

Fault Detection Isolation & Diagnosis Process


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Fault Detection, Isolation & Diagnosis Process

RootCauses

Collect Data

Clean

Data

DiagnoseFaults

Simulate

RawData

MeasuredPerformance

Routing updates,Link Loads

Signal Strength

Inject

CandidateFaults

Performance

Estimate

Agent Module

ManagerModule

SNMP MIBsPerformance CountersWRAPIMCLNative WiFi

Steps to diagnose faultsEstablish normal behavior

Deviation from the normal behavior indicates a potential fault

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

R t C A l i M d l


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Wireless

Network

Simulation

Link RSS

Link Load

Routing Update

+/-

Loss rate,

Throughput, Noise,

Faults

Directory

N

E

T

W

O

R

K

R

E

P

O

RT

S

Expected Loss rate,

Throughput, Noise,...

Error

Topology

Changes

Interference

Injection

Error

{Link, Node,

Fault}

Traffic

Simulation

Delay

Root Cause Analysis Module

T bl h ti F k


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Troubleshooting FrameworkAdvantages

Flexible & customizable for a large class of networks

Captures complicated interactions within the network

between the network & environment, and

among multiple faultsExtensible in its ability to detect new faults

Facilitates what-if analysis

ChallengesAccurately reproduce the behavior of the network inside asimulator

Build a fault diagnosis technique using the simulator as adiagnosis tool

Di i P f


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Diagnosis Performance

Number offaults

4 6 8 10 12 14

Coverage 1 1 0.75 0.7 0.92 0.86FalsePositive

0 0 0 0 0.25 0.29

25 node random topology

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


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Testbeds & Trials

T tb d


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TestbedsDetails

60 (Bldg. 32) + 25 (Bldg. 112) nodes

Inexpensive desktops (HP d530 SF)Two 802.11 radios in each node

NetGear WAG or WAB, Proxim OriNOCO

Cards can operate in a, b or g mode.

PurposeVerification of the mesh software stack

Routing protocol behavior

Fault diagnosis and mesh managementalgorithms

Security and privacy architecture

Range and robustness @ 5 GHz withdifferent 802.11a hardware

Stress TestingVarious methods of loading testbed:

Harpoon traffic generator (University ofWisconsin)

Peer Metric traffic generator

Ad-hoc use by researchers

205

201

204

203

210

226

220

227

221

225

224

206

211

207

208

209

219

215

216

218

217

214

223

Approx.61m

Approx. 32 m

R d d A t t T i l


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Redmond Apartment Trials

MicrosoftCampus

32 Bellaire Apts

31

UNIT FF UNIT GG

Road

UNIT HH20 Feet

ControlApt

GG302

Road

Parking Lot

FF203

UNIT CC

UNIT BB

Carport

BB103

BB302

BB201

ControlApt

GG302

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

R d d A t t T i l


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Redmond Apartment Trial

Control Apt GG302 Mesh Box

Mesh Hall (Kitchen)Apt FF201

C b id UK T i l


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Cambridge 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 ehometo create a mediasharing demo in collaboration with ZCast DVB trial

Deployed by The Venice Team

M h Vi li ti M d l


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Mesh Visualization Module


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Data Channel Radio

Miniport 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

S

E

C

U

R

I

T

YDiagnostics Kernel

Module

Diagnostics Client

and Server DLLs

Resources


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Resources

Software, Papers, Presentations, articlesURL: http://research.microsoft.com/mesh/

Mesh Research Academic Resource KitContact: [email protected]

Mesh Networking Summit 2004Videos, Presentations, Notes etc.

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

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