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.

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Outline

• Introduction• Motivation• Problem Definition• Related Work• RINGS : Lookup Service• Analysis and Comparison• Simulation Results• Directions for Future Work and Conclusion

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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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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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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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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• 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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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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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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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,

Where K = 2, 4, 6, …

2/)1)(log( KNL

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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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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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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,

• 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,

/2 Nd

)log(* NdLchord

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Analysis (Cont…)

• For RINGS,– Query lookup cost at first hop is,

• 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,

)log(NLRINGS

...)1)(log()1)(log(1(*)log( 2 NNNLRINGS

))1)(log(... 12/ KN

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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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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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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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Thank You