MANET Supernodes

1
MANET Supernodes

• March 16, 2005
• Barry Demchak
• Zhong-Yi Jin
• William Chang

2
Problem

• How to create a file system on a MANET that is
  reliable, energy efficient, and has low latency?

3
MANET

• Mobile Ad-hoc NETwork
• Characteristics
• Wireless
• Energy constrained
• Transient nodes
• Nodes are hosts

and routers
4
Related Works

• Ekta
• DHT substrate on MANET
• Not a file system
• Not energy efficient
• Pangaea
• Meta-data/data replication
• Not on MANET

5
Our Approach

• Group nodes into Supernodes

6
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

7
Goals

• Reliability
• Low latency
• Energy efficiency

Replication of meta-data and data
Node group coverage
Node group coverage Meta-data propagation
optimization
8
Architecture
9
Project Scope
10
Join
11
File Retrieve
M
M
M
M
D
D
12
File Retrieve (Retro)
M
M
M
M
M
D
D
M
13
File Save
D
14
Meta-data Propagation

• Forward to every neighbor
• Poison list optimization

M
M
M
M
M
M
M
M
M
M
15
Experiment

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

16
P2PSim
17
Reliability
Sweet spot at 3-5 nodes per supernode
18
Reliability (cont.)
With few nodes per supernode, odd are that
supernode will die before data node
19
Reliability (cont.)
3 nodes per supernode seem sufficient
for protection of up to 5 file copies
20
Energy
Larger supernodes have edges closest to
any particular node on network
21
Energy (cont.)
Latency and energy drop because of
spatial locality due to more file copies
22
Scenario A
M
23
Scenario B
M
M
M
M
24
Latency
Assuming 1400 bytes/packet, large files
simply involve more packets
25
Poison List
Poison list is important energy optimization
definitely worth space in packet
26
Poison List (cont.)
Poison list shorter than number of nodes
in supernode causes energies and
latencies non-linear with respect to supernode
size
27
Poison List (cont.)
Supernode update energy is linear with respect to
supernode size
28
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

29
Connect Group to Ring
30
(No Transcript)
31
Reduce total Number of Joins
Number of Joins Our Chord
128 Nodes 102/120/4 218
512 Nodes 555/1506/131 2075
32
Performance
Super node
Child Node
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Conclusion

• Reliability achieved through replication of
  meta-data and data
• Low latency energy efficiency achieved through
  node grouping
• Scalability traded for energy efficiency

34
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

35
Q A

36
Thank You