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DCMP: A Distributed Cycle Minimization Protocol for Peer-to-Peer NetworksAuthors: Zhenzhou Zhu, Panos Kalnis and Spiridon BakirasSource: IEEE Transactions on Parallel and Distributed

Systems, Vol. 19, no. 3, pp. 363-377, 2008Speaker: Huan-Chin Hsu ( 徐煥欽 )Date: 12/03/2010

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Outline• Introduction

– Unstructured P2P– Concepts

• The Proposed Method• Experimental Results• Conclusions• Comments

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Unstructured P2P

TTL (Time To Live)

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Concepts• DCMP: Distributed Cycle

Minimization Protocol– Reduce 90% duplicate messages.– Require few control messages.

(overhead is minimal)– Suitable for dynamic network.– There is a trade-off between eliminating

the cycles and maintaining the connectivity.

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The Proposed Method (1/9)• Notation

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The Proposed Method (2/9)• Simplistic Cycle Elimination (SCE)1. A→B with GUID(msgi) 2. A'→B with GUID(msgi) 3.Cut

1. E→C 、 E→D with GUID(msgj)

2. A→C 、 A'→D with GUID(msgj)

3.Cut

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The Proposed Method (3/9)• DCMP1. B→A with GUID(msgi) 2. F→A with GUID(msgi) 3. Propagate Information

Collecting (IC) message DirectionID(icmi) = F→A4. A→B 、 A→F with icmi ….

Structure of the IC message.

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The Proposed Method (4/9)• DCMP

5. D Combine NIV6. D compute the Power of peers7. Let B be the GatePeer Decide to cut 8. Propagate Cut Message (CM)9. E cut

Structure of the Cut Message.

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The Proposed Method (5/9)• Disseminating GaterPeer

information– Tagging message with (NIVGP,

HopsNumber)– 1 message / 5 seconds (a period of 1

minute)– 1 message / 10 minutes– The overhead of tagging is small

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The Proposed Method (6/9)• B and F are GatePeers• D is a transitive peer• transitive peer as

a GatePeer

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The Proposed Method (7/9)• Concurrent Cycle

Elimination– Measure power P by degree– C is the GatePeer of ABCDEA– F is the GatePeer of ABGFEA– The connection opposite to C

is AE– The one opposite to F is

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The Proposed Method (8/9)• Failure of normal peer B

– A is the referred GatePeer of both C and D

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The Proposed Method (9/9)• Dynamic network

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List of Backup GatePeers (2~5)

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Experimental Results(1/6)• Evaluation by Simulation

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Experimental Results(2/6)

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Experimental Results(3/6)

• 3000 nodes, TTL = 8• Bandwidth ranged from 56 Kbps – 45 Mbps• 3.6 queries per peer per hour

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Experimental Results(4/6)

• 3000 nodes and addition 3000 nodes• Replace nodes at a session time

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Experimental Results(5/6)• Prototype Evaluation on PlanetLab

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Experimental Results(6/6)

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Conclusions• They presented DCMP, a protocol for

distributed cycle minimization in broadcast-based P2P systems.

• Eliminating most of the duplicate messages.

• Overhead due to control messages is minimal.

• The protocol is suitable for dynamic network confirmed by experimental results.

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Comments• Some obvious mistake of

typesetting.• They didn’t consider about download

files.• It’s not sure for applied in two-layer

network.