1. 03/19/02Scalab Seminar Series1 Finding Good Peers in Peer-to-Peer Networks Ramaswamy N.Vadivelu Scalab, ASU

2. 03/19/02Scalab Seminar Series2 Introduction Ramanathan, Kalogeraki,Pruyne P2P models: Decentralization by distribution. No central authority Broadcasting Network topology: Arbitrary and Dynamic Bandwidth vs. No.of messages and peers

3. 03/19/02Scalab Seminar Series3 “Good “ peers and their “Interests”. Nodes with high degree of interests are good !. Proposed mechanism…. Advantages: Reduces the number of messages in the network Allocates resources Scales well. Assumptions: Connectivity Non unique files

4. 03/19/02Scalab Seminar Series4 System Model Logical network of nodes. Immediate Indirect Note:  Non connected nodes! Each Peer maintains: Meta-data, p-c, p-m and p-d. p-b

5. 03/19/02Scalab Seminar Series5 Constraint: Sum [p-b(q)] < p-b Limit the number of connections ( p-c ) per peer. The horizon : h-p Metrics: imp(q) Queryhits(q) Avhops(q) Connectime(q)

6. 03/19/02Scalab Seminar Series6 Finding Good Peers 1)Minimize h(q). 2)Maximize prob of connecting similar peers. Each peer maintains a dynamic peer-list. Fallback: Central server! Communication through specified messages. TTL, group_id Connection accepted based on metrics.

7. 03/19/02Scalab Seminar Series7 Searching in the Network Through query messages with constraints. Query – Query-Hit message Path retraced, TTL decremented. Results are buffered and displayed. Reputation metrics Results are used to determine the ‘good’ peers.

8. 03/19/02Scalab Seminar Series8 Horizon Indirect peers through Immediate peers. View of indirect peers. Inverser relation to importance Large av.number of hops, =>nodes farther off.  No replies,does that mean its not a good peer?

9. 03/19/02Scalab Seminar Series9 No,because May give results for other queries. May lose connections to other indirect nodes. So we calculate “ Importance”. Sequence of weighted measurements,not the average.

10. 03/19/02Scalab Seminar Series10 Good peers are those with high importance. Good peers provide: High percentage of queryhits Are connected over a long period of time. Long time connectivity is a strong indication that they have the same interests.

11. 03/19/02Scalab Seminar Series11 Periodic evaluation of peers. When perc QueryHits (s) > min perc QueryHits of immediate neighbors. Max_Connections. Stability is related to rate of Peer selection.

12. 03/19/02Scalab Seminar Series12 Peer Selection Algorithm

13. 03/19/02Scalab Seminar Series13 Experimental Results Two scenarios: 1.Finding peers with similar interests 2.Adapting a peer’s connections, as interests are changed.

14. 03/19/02Scalab Seminar Series14 Discussion: