1 A connection management protocol for promoting cooperation in Peer-to-Peer networks Authors: Murat Karakaya, Ibrahim Korpeoglu, and Ozgur Ulusoy Source: Computer Communications, vol. 31, pp. 240 – 256, 2008 Speaker: Shu-Fen Chiou ( 邱淑芬 )

2 Outline Introduction Gnutella Free rider Proposed scheme P2P Connection Management Protocol (PCMP) Simulation result Attacks Conclusion Comments

3 Introduction Gnutella (Host Cache) It is a pure P2P protocol in contrast with Napster It is a broadcast-type network The core of the protocol consists of 5 descriptors PING, PONG, QUERY, QUERY HIT and PUSH A Peer needs to connect to 1 or more other Gnutella Peers in order to participate in the network Gnutella Network N Server p QUERY 1 QUERY HIT 2 Server p2

4 Introduction Find Hosts Gnutella

5 Introduction Ping Gnutella

6 Introduction Pong Gnutella

7 Introduction Pong Gnutella

8 Introduction Pong Gnutella

9 Introduction Query Gnutella

10 Introduction Query TTL=2 Gnutella

11 Introduction queryQuery TTL=3 Gnutella

12 Introduction Query Hit Gnutella

13 Introduction Download File Gnutella

14 Free rider Download File Query Free rider

15 Proposed scheme Proposed two connection types. Proposed a P2P Connection Management Protocol (PCMP). Benefits: The connectivity of free riders to the contributing peers can be reduced. In some situations, free riders can be totally isolated from the contributors. The connectivity among contributor peers can be increased. The workload of a contributor peer can be reduced, since it will not serve many free riders anymore.

16 General P2P connection

17 Two connection types IN-connection and OUT-connection Limiting the numbers of connection. IN-connection OUT-connection

18 P2P Connection Management Protocol (PCMP) 2 IN-connections, 2 OUT-connections A B Download file C D IN-connection Requester (Downloader) Responder (Uploader) A According download times(C-PCMP) or update time (T-PCMP) IN-connection B OUT-connection Ping Pong

19 P2P Connection Management Protocol (PCMP) 4 IN-connections, 4 OUT-connections TTL=2 Contributor F1, F3 F2 Query F1

20 P2P Connection Management Protocol (PCMP) Contributor F1, F3 F2 Query F2

21 Simulation results 900 peers

22 Attacks Malicious peer refuse to add a contributor to its list of IN-connections after downloading file. Contributors establish OUT-connections only with other contributors. This attack will not affect.

23 Attacks A malicious peer replies with a faked Query Hit. In PCMP, the connection between two peers is established after a file is download. If the file is wrong, the downloader will not send Pong message.

24 Attacks A malicious peer behaves as a new- comer to gain more OUT-connections. Try to reduce this attack according others ’ methods.

25 Conclusion Proposed a novel approach and a P2P Connection Management Protocol (PCMP).

26 Comments Prevent the third attack. Increase its OUT-connections by: Increasing answering power. Increasing the number of edges. Increasing the amount of capacity used to service neighbors ’ queries. Increasing the length of period for servicing neighbors ’ queries.