1 DCMP: A Distributed Cycle Minimization Protocol for Peer- to-Peer Networks Authors: Zhenzhou Zhu, Panos Kalnis and Spiridon Bakiras Source: IEEE Transactions on Parallel and Distributed Systems, Vol. 19, no. 3, pp , 2008 Speaker: Huan-Chin Hsu ( 徐煥欽 ) Date: 12/03/2010

2 Outline Introduction –Unstructured P2P –Concepts The Proposed Method Experimental Results Conclusions Comments

3 Unstructured P2P TTL (Time To Live)

4 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.

5 The Proposed Method (1/9) Notation

6 The Proposed Method (2/9) Simplistic Cycle Elimination (SCE) 1. A → B with GUID(msg i ) 2. A' → B with GUID(msg i ) 3.Cut 1. E → C 、 E → D with GUID(msg j ) 2. A → C 、 A' → D with GUID(msg j ) 3.Cut

7 The Proposed Method (3/9) DCMP 1. B → A with GUID(msg i ) 2. F → A with GUID(msg i ) 3. Propagate Information Collecting (IC) message DirectionID(icm i ) = F → A 4. A → B 、 A → F with icm i …. Structure of the IC message.

8 The Proposed Method (4/9) DCMP 5. D Combine NIV 6. D compute the Power of peers 7. Let B be the GatePeer Decide to cut 8. Propagate Cut Message (CM) 9. E cut Structure of the Cut Message.

9 The Proposed Method (5/9) Disseminating GaterPeer information –Tagging message with (NIV GP, HopsNumber) –1 message / 5 seconds (a period of 1 minute) –1 message / 10 minutes –The overhead of tagging is small

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

11 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

12 The Proposed Method (8/9) Failure of normal peer B –A is the referred GatePeer of both C and D

13 The Proposed Method (9/9) Dynamic network List of Backup GatePeers (2~5)

14 Experimental Results(1/6) Evaluation by Simulation

15 Experimental Results(2/6)

16 Experimental Results(3/6) 3000 nodes, TTL = 8 Bandwidth ranged from 56 Kbps – 45 Mbps 3.6 queries per peer per hour

17 Experimental Results(4/6) 3000 nodes and addition 3000 nodes Replace nodes at a session time

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

19 Experimental Results(6/6)

20 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.

21 Comments Some obvious mistake of typesetting. They didn’t consider about download files. It’s not sure for applied in two-layer network.