manet supernodes march 16, 2005 barry demchak zhong-yi jin william chang
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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