MANET Supernodes

March 16, 2005

Barry DemchakZhong-Yi Jin

William Chang

Problem How to create a file system on a

MANET that is reliable, energy efficient, and has low latency?

MANET Mobile Ad-hoc NETwork Characteristics

Wireless Energy constrained Transient nodes Nodes are hosts and routers

Related Works Ekta

DHT substrate on MANET Not a file system Not energy efficient

Pangaea Meta-data/data replication Not on MANET

Our Approach Group nodes into Supernodes

M

M

M

M

M

D

D

D

M – Meta DataD – DataHash(D) = SN3

SN3

SN1

SN4

SN3SN2

SN5

Components Supernode – group of nodes sharing a

common set of meta-data Meta-data – information about the

locations and the name of data Data – shared file residing at one or

more nodes Hash() – consistent hashing value of

data name

Goals Reliability

Low latency

Energy efficiency

Replication of meta-data and data

Node group coverage

Node group coverageMeta-data propagation optimization

Architecture

PacketDelivery

RouteDiscovery

Join /Leave

Split /Merge

Meta-DataSave/Retrieve

File Save/Retrieve

PictureViewer

ResultsGrabber

File SystemReplication

Meta-DataReplication

Application

File System

Supernode Level Routing

Node LevelRouting

FileList

FileDelete

Project Scope

PacketDelivery

RouteDiscovery

Join /Leave

Split /Merge

Meta-DataSave/Retrieve

File Save/Retrieve

PictureViewer

ResultsGrabber

File SystemReplication

Meta-DataReplication

Application

File System

Supernode Level Routing

Node LevelRouting

FileList

FileDelete

Join

File Retrieve

DM

M

M

M

D

File Retrieve (Retro)

D

M

M

M

M

DMM

M

M

M

File Save

M

M

M

M

D

Forward to every neighbor Poison list optimization

Meta-data Propagation

M

M

M

M

M

M

M

M

M

M

Experiment Simulated on P2PSim Measure reliability Measure energy / latency Measure poison list optimization

P2PSim

NodeNodeNodeNodeEvent Queue

EventGenerator

EventProcessor

ProtocolSimulator

TopologyPacket

Routing

Network Simulator

Reliability

File Loss Due to Node Deaths

0.00

10.00

20.00

30.00

40.00

50.00

0 5 10 15

Nodes in Supernode

Cra

shed

No

des

Net

wo

rk-

wid

e

1 File

3 Files

5 Files

Sweet spot at 3-5 nodes per supernode

Reliability (cont.)

With few nodes per supernode,odd are that supernode will die before data node

File Loss Due to Metadata Loss (as compared to data loss)

0.00

1.00

2.00

3.00

4.00

5.00

0 5 10 15

Nodes in Supernode

Rat

io o

f M

etad

ata

Fai

lure

to

No

des

in

Su

per

no

de 1 File

3 Files

5 Files

Reliability (cont.)

3 nodes per supernode seem sufficient forprotection of up to 5 file copies

File Loss Due to Node Deaths

0.00

10.00

20.00

30.00

40.00

50.00

0 1 2 3 4 5

File Count

Cra

shed

No

des

Net

wo

rk-

wid

e

1 Node

3 Nodes

5 Nodes

10 Nodes

14 Nodes

Energy

Larger supernodes have edges closest to anyparticular node on network

Energy & Latency (Metadata Access) vs Nodes in Supernode

0

20

40

60

80

100

120

140

0 2 4 6 8 10 12 14 16

Nodes in Supernode

En

erg

y &

Lat

ency

Energy (cont.)

Latency and energy drop because of spatiallocality due to more file copies

Latency & Energy (Data Read) vs Duplicate Files

0

50

100

150

200

250

300

0 1 2 3 4 5

Duplicate Files

Lat

ency

& E

ner

gy

Scenario A

M

Scenario B

M

M

M

M

Latency

Assuming 1400 bytes/packet, large files simplyinvolve more packets

Transit Time vs Bytes

0

200

400

600

800

1000

1200

1400

1600

1800

0 2000 4000 6000 8000 10000 12000 14000

Bytes

Tran

sit

Tim

e

Poison List

Poison list is important energy optimization –definitely worth space in packet

Poison List Size vs Metadata Write Energy

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 5 10 15

Poison List Size

Met

adat

a W

rite

En

erg

y

1 Node

3 Nodes

6 Nodes

10 Nodes

16 Nodes

Poison List (cont.)

Poison list shorter than number of nodes insupernode causes energies and latenciesnon-linear with respect to supernode size

Effects of Poison List

0

1

2

3

4

5

6

7

8

9

0 0.2 0.4 0.6 0.8 1 1.2

poison list / supernode size

Pen

alty

(x

op

tim

al)

3

6

10

16

Poison List (cont.)

Supernode update energy is linear with respectto supernode size

Metadata Write Energy vs Supernode Size (assuming adequate poison list)

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14 16

Supernode Size

Met

adat

a W

rite

En

erg

y

Routing among Groups Apply DHT (Chord) to MANET Characteristics of wireless network

Locality: Shared media, limited range Mobility: Fast node join/leave Limited capability: Distribute Load

Connect Group to Ring

Join Chord Ring

Join the groupRequest super node’s chord info

Super node Child Node

Super node

Child Node

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Series1

106

120

218

0

0

50

100

150

200

250

Our Chord

Number of Joins in a stable environment, 128 Nodes Topology

Series2

Series1

686

1506

2075

0

500

1000

1500

2000

2500

Our Chord

Number of Joins in a volatile environment, 512 Node Topology

Series2

Series1

Number of Joins Our Chord

128 Nodes 102/120/4 218

512 Nodes 555/1506/131 2075

Reduce total Number of Joins

Performance

Lookup completed in maxlookuptime=1500 Our Chord Our Chord64 Nodes 0.117 0.248 0.103 0.296

128 Nodes 0.056 0.1280.038

(0.053) 0.128

Without stablization With stablization

Super node

Child Node

Conclusion Reliability achieved through

replication of meta-data and data Low latency & energy efficiency

achieved through node grouping Scalability traded for energy

efficiency

Future Work Routing layer Merge/Split supernodes File delete/modify File listing More realistic experiments

Mix node join and crash Realistic routing latency Realistic energy cost Packet loss

Q & A

Thank You