Gateway Selection in Rural Wireless Mesh Networks
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Gateway Selection in Rural Wireless Mesh Networks Team: Lara Deek, Arvin Faruque, David Johnson. http://www.octavetech.com/blog/wp-content/uploads/2008/03/long-range-wireless.jpg. Introduction: Rural Wireless Mesh Networks (WMNs) ‏.

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Slide1 l.jpg

Gateway Selection in Rural Wireless Mesh Networks

Team: Lara Deek, Arvin Faruque, David Johnson

http://www.octavetech.com/blog/wp-content/uploads/2008/03/long-range-wireless.jpg


Slide2 l.jpg

Introduction: Rural Wireless Mesh Networks (WMNs)

  • A mesh network comprised of multiple, commodity devices that provides Internet access to rural areas

  • Topology differs from hub-and-spoke wireless networks

  • Applications: Education, health care

  • Benefits: cost, robustness, infrastructure requirement


Slide3 l.jpg

Introduction: Rural WMN Examples

  • Digital Gangetic Plains (India)‏

  • OLPC Project:

    Each XO-1 will operate as a WMN node

Image from http://www.cse.iitk.ac.in/users/braman/dgp.html

Image from

http://laptop.org/en/laptop/hardware/specs.shtml


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Introduction: Mesh Network Gateway Selection

  • Mesh networks connect to the rest of the Internet via gateways

  • Rural and municipal WMNs have different bandwidth constraints

    • Municipal: bottleneck is wireless links

    • Rural: bottleneck is at gateways

  • Problem: Inefficiently utilized gateways WMN can have severe consequences in rural areas

  • Our goal: modify an existing mesh routing protocol attempt to optimally select gateways


B a t m a n 1 l.jpg
B.A.T.M.A.N.(1)‏

A

B

F

D

G

C

X

E

A wants to reach X


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B.A.T.M.A.N. (2)

Nodes broadcast originator messages (OGM's) every second

OGM's are rebroadcast

Other nodes measure how many OGM's are received in a fixed time window

A:10

A

B

F

D

A:9

G

C

X

E


B a t m a n 3 l.jpg
B.A.T.M.A.N. (3)‏

A

B

F

A:8

D

G

C

A:7

X

E

A:7

D BATMAN routing table

TO VIA Q

A B 8

A C 7

D Final routing table

TO VIA

A B


B a t m a n 4 l.jpg
B.A.T.M.A.N. (4)‏

A

B

F

A:0

A:6

D

G

C

A:4

X

A:7

E

G BATMAN routing table

TO VIA Q

A D 6

A E 7

G Final routing table

TO VIA

A E


B a t m a n 5 l.jpg
B.A.T.M.A.N. (5)‏

A

B

F

D

G

A:5

C

X

A:6

E

X BATMAN routing table

TO VIA Q

A G 5

A E 6

X Final routing table

TO VIA

A E


B a t m a n 6 l.jpg
B.A.T.M.A.N. (6)‏

A

B

F

D

G

C

X

E

X BATMAN routing table

TO VIA Q

A G 5

A E 6

E BATMAN routing table

TO VIA Q

A C 7

A D 4

C BATMAN routing table

TO VIA Q

A A 9


Current gw selection techniques l.jpg
Current GW selection techniques

Minimum hop count to gateways

Used by routing protocols like AODV

Creates single over congested gateways

GW2

A

B

F

D

G

C

X

E

GW1


Current gw selection techniques12 l.jpg
Current GW selection techniques

Best link quality to GW

Used by

source routing protocols like MIT Srcr

Link state protocols like OLSR

Prevents congested links to GW

Not global optimum of GW BW usage

GW2

2

2.2

A

B

F

1.5

1

1

3

D

G

C

1

X

1

1

E

GW1


Current gw selection techniques13 l.jpg
Current GW selection techniques

BATMAN has advanced a little further

GW can advertise downlink speed

User can choose GW selection based on

GW with best BW

Stable GW (need history)‏

GWBW x LQ

Can't trust advertised GW BW

Doesn't achieve fairness

256 kbps

GW2

9

10

A

B

F

7

4

7

3

D

G

C

8

7

X

E

10

512 kbps

GW1


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Proposed Solution: Introducing intelligence to the core of the WMN

  • Introduce information about gateway performance into the network

  • Nodes at “intelligence boundary” have gateway performance information, need to transfer this information to the other nodes

  • Transfer this information via: “Batsignal” packets that are flooded through the network


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Proposed Solution: What does the boundary node measure? the WMN

  • When nodes will select gateways, they will need to estimate the amount of bandwidth they will get:

  • Example:

  • Hence, boundary nodes must transmit current total gateway bandwidth and current # of VPNs

  • Total gateway capacity is the sum of

    • Measured extra bandwidth (measured through active probes)

    • The sum of the current bandwidths of the VPNs


Slide16 l.jpg

Field the WMN

Description

GWID

Gateway ID (0-255)‏

TS

Time stamp

DB

Total download bandwidth

VPNs

Number of VPNs on gateway

TTL

Packet time to live

Proposed Solution: Batsignals

  • A node at the intelligence boundary periodically

    • Record gateway measurement

    • If the measurement is not drastically different than a previous value, then transmit a Batsignal packet only if we have not recently transmitted a batsignal packet

    • If the measurement is drastically different from a previous value, immediately transmit a Batsignal packet

  • All other nodes

    • Forward a received bat-signal to its neighbors (if it has not expired)‏

    • Update their own gateway preference tables

Batsignal Packet

Node Gateway Preference Table


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Proposed Solution: Using Batsignal data to pick a gateway the WMN

Gateway Preference Table

  • To choose a gateway, the following metric based on table data and link quality (computed only when current_time - timestamp is below a threshold) is used

  • Gateway flapping: When a gateway comes up and goes down frequently, a large number of conflicting Batsignal's will be broadcasted to the WMN nodes.

    • The VPN will not switch to another gateway until all the flows within it have terminated (Srcr)



Evaluation the massive mesh in south africa l.jpg
Evaluation: The massive mesh in South Africa the WMN

7x7 grid of 49 wireless nodes using 802.11 a/b/g radios

Each node network boots off a central server

Makes use of 30dB attenuators on radios to achieve multiple hops in small space

Has been used for extensive mesh network protocol benchmarking

Complete remote control of experiments possible


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Evaluation Environment I the WMN

Parameters at the Gateway and Mesh Nodes

Technologies Used

  • Load: traffic/congestion.

  • Loss: signal weakness, obstacles.

  • Delay: .

  • Bandwidth: of the available communication channels between mesh nodes or between mesh nodes and gateways.

  • Throughput: between mesh nodes and a test server outside the mesh network.

  • tc: linux traffic control.

  • iperf: TCP/UDP bandwidth measurement tool.

  • iptables: defines packet processing schemes.


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Evaluation Environment II the WMN

Metrics

Measurement Methodology

  • Gateway efficiency: measures how effectively we match the throughput generated by the VPNs to the capacities of the gateways.

  • Gateway fairness: measures how fairly the aggregate gateway throughput is distributed among VPN flows.

  • Gateway Flapping: measures the frequency a mesh node switches between utilization of multiple gateways.

  • Measure VPN flows at each GW

  • Have capacity of all GW’s.

  • Measure VPN flows. What is the time window? Average over time.

  • Parse BatSignals for each node and record the timestamp for each GW usage. How much hysteresis?


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How are we using technologies to determine fundamental parameters?

Active Probing to determine GW throughput using a decentralized, distributed approach via trusted internet mesh nodes that form the intelligence boundary {B1, B2}.


Slide23 l.jpg

Current Progress (from Proposal) parameters?

We are in Week 4.

Formulate a set of preliminary evaluation metrics for the protocol. (Week 1 - Week 3). Done

Formulate a measurement procedure to test the efficacy of the protocol. (Week 1 - Week 2) Done

Emulate a gateway on a UCSB MeshNet node using Linux tools such as tc and iptables. (Week 2 - Week 3)Have developed scripts to control TC and iptables. Need to develop remote control for this script.

Run and evaluate the latest developers release of B.A.T.M.A.N. on the UCSB MeshNet. (Week 1 - Week 4) Have evaluated BATMAN on 3 mesh UCSB MeshNet nodes. Need to transition massive mesh (has been done before).

Implement solutions to Goals 1, 2, 3, and 4 and measure performance using the measurement process described in (2) and evaluation metrics described in (1) (Week 3 – Week 6) In progress, analyzing code.


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Nifty Animations parameters?


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