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Lookup Service for Peer-to-Peer
Systems in Mobile Ad-hoc
Networks
M. Tech Project Presentation
By,
Kalpesh Patel
02329027
Guided By,
Dr. Sridhar Iyer,
Dr. Krishna Paul.
09/07/2004
Peer-to-Peer Systems in Mobile
Ad-hoc Networks
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Outline
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Introduction
Motivation
Problem Definition
Related Work
RINGS : Lookup Service
Analysis and Comparison
Simulation Results
Directions for Future Work and Conclusion
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Peer-to-Peer Systems in Mobile
Ad-hoc Networks
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Introduction
• Peer-to-Peer Systems
• Nodes share files and services among other nodes
in P2P network.
• Mostly focuse on wired network.
• Mobile Ad-hoc Networks
• MANET is an autonomous system for mobile hosts
over wireless links.
• Multi-hop scenario.
• Mobility.
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Ad-hoc Networks
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Motivation
• Why P2P in MANET?
• What happens if existing P2P
protocols are deployed in
MANET?
– Neighbours at application layer
may not necessarily be
neighbours at network layer.
• Problems with existing
MANET protocols
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Ad-hoc Networks
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Problem Definition
• The overall objective is to efficiently deploy P2P
applications in Mobile Ad-hoc Networks.
• Specifically, need of a network layer protocol which
optimizes query lookup service.
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Ad-hoc Networks
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Related Work
• Mobile Peer-to-Peer Protocol (MPP) : Recent work on P2P in mobile
environment.
• Reference : Rudiger Schollmeier, Ingo Gruber, Michael Finkenzeller,
Protocol for Peer-to-Peer Networking in Mobile Environments.
• The problem is, MPP still relies on flooding at network layer.
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RINGS : Lookup Service
• Basic Protocol - Advertisement
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Network layer gets index from application layer.
Node broadcasts its data index into the network.
Every K-hop nodes keep index for a given node.
This process is followed by every node in the network.
• Basic Protocol – Query lookup
• Node forwards the query to its neighbors.
• Due to equal distribution of indices throughout the
network, query is answered within K/2 hops.
• So, Upper bound for query lookup is K/2 hops.
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Ad-hoc Networks
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RINGS : Cont…
• Basic protocol makes a
set of imaginary circles for
a given source node as
shown in Fig.1.
• Fig. 2 shows an example
of 2-hop (K=2) scenario.
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Ad-hoc Networks
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RINGS : Cont…
• Route Maintenance
– Advertise packet maintains route to the source node.
– This is accomplished by maintaining reverse route on the
path.
– A node, which stores the index, keeps this route along
with other information.
– If a query comes to this node, it responds with query
result as well as route to the source.
– An optimal route.
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Ad-hoc Networks
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RINGS : Cont…
• Mobility
– Mobility has none or little impact on the performance of the
protocol.
– In average, number of neighbors per node in mobile network can
be taken as log(N).
– So, even if as much as log(N) -1 nodes moves away from the
network, node gets at least one node for query result.
– Thus, a node gets at least one node which can satisfy its query
even if L number of nodes from nearest circle leave the network,
where L is,
L  (log( N )  1) K / 2
Where K = 2, 4, 6, …
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RINGS : Cont…
• Optimization
– Data Updates
• Updates are sent to only those nodes which have stored indices for
the source node.
– Node Joining
• Whenever a new node joins the network, it gets some share of
indices from its neighbors.
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Ad-hoc Networks
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RINGS : Cont…
• Node Deletion
– Neighbors of leaving node search for an alternative
route.
– After getting alternative route, indices are reallocated
according to index-hop (K) value.
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Ad-hoc Networks
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Analysis
• Goal
• Count the ‘actual’ query lookup cost for P2P protocol like
‘Chord’ in MANET.
• The average distance d between any two nodes at the network layer
can be taken as,
d  2 N / 
• Now, query lookup cost for Chord in application layer is log(N).
• Actual cost = App. Layer cost + Network layer cost.
• So, effective lookup cost Lchord for chord protocol is,
Lchord  d * log( N )
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Analysis (Cont…)
• For RINGS,
– Query lookup cost at first hop is,
LRINGS  log( N )
• In turn, each of these log(N) nodes forwards query to
its neighbors.
• Continuing this way, query lookup cost at the nearest
K-hop is,
LRINGS  log( N ) * (1  (log( N )  1)  (log( N )  1) 2  ...
...  (log( N )  1) K / 21 )
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Simulation Results
• An important measure is, how average number of remote
indices stored per node increases as the value of K increases.
• Result indicates that, as value of K increases, average number
of remote indices per node increases very fast.
• Value K = 4 balances both the metrics.
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Simulation Results (Cont…)
• Graph shows comparison between query lookup costs Lchord
and LRINGS
• For the value of K = 4, RINGS performs better than Chord in
terms of query lookup cost.
• For the value of K = 6, as the number of nodes increases
beyond a certain number, RINGS performs better than Chord.
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Ad-hoc Networks
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Comparison
• Why RINGS?
– Most recent work still relies on network layer flooding
for query lookup.
– Most adopted MANET protocols like AODV, DSR
uses broadcast technique, results in flooding the
whole network every-time when a search for a node
requires.
– P2P protocols
• Gnutella uses broadcast.
• Chord assigns every node a virtual identifier independent of
actual locations, which is not preferable at network layer.
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Directions for Future Work
• RINGS assumes enough storage space available at the
node. There is a scope of improvement to reduce this
overhead.
• Effective mobility handling.
• Practical applications.
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Ad-hoc Networks
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Conclusion
• There is a need to combine P2P applications and Ad-hoc
systems to share data among mobile users.
• Current P2P protocols fail to perform well with this
combination.
• An initial step to this problem is RINGS, which focuses on
query lookup cost optimization.
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Ad-hoc Networks
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Thank You
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Ad-hoc Networks
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