1. UNIVERSITY OF JYVÄSKYLÄ Chedar: Peer-to-Peer Middleware Presentation for 8 th International Workshop on Java tm for Parallel and Distributed Computing (IWJPDC 2006) 25.4.2006 Annemari Auvinen, research student Department of Mathematical Information Technology University of Jyväskylä, Finland http://tisu.it.jyu.fi/cheesefactory With co-authors Mikko Vapa, Niko Kotilainen, Matthieu Weber and Jarkko Vuori

2. UNIVERSITY OF JYVÄSKYLÄ Agenda Peer-to-Peer Networks Chedar Chedars Structure Messages Topology Management Algorithms

3. UNIVERSITY OF JYVÄSKYLÄ Peer-to-Peer Networks Peer-to-Peer (P2P) networks allow sharing of resources (e.g., computing power, storage space) over the Internet Every node serves as a server and a client In contrast to clusters, in P2P networks all the tasks and responsibilities for managing the network are shared between peers

4. UNIVERSITY OF JYVÄSKYLÄ Related Work Gnutella –Pure P2P protocol –Search queries are broadcasted by using BFS with TTL –Pre-defined amount of neighbors Chedar differs: –Middleware –Topology management algorithms –4 search algorithms –Resource reply routing –XML-based structured resource description

5. UNIVERSITY OF JYVÄSKYLÄ Chedar Chedar is a totally decentralized P2P middleware implemented using Java Neighbors goodness is defined based on the resource replies the node has received from the neighbor Basis for P2P applications: distributed computing (P2PDisCo), data fusion, extension for mobile devices

6. UNIVERSITY OF JYVÄSKYLÄ Structure 1/3 ChedarClient –API for Chedar startConnecting() setMonitor(iMonitor) pingMessage() setResources(resource) createResourceQuery(query, algorithm, ttl) setTrafficLimit(limit) forceConnection(id) forceDisconnection(id) closeAllConnections –By implementing a monitoring interface iMonitor the application may get events about sent and discarded queries, forwarded messages, sent replies, received replies and connection requests

7. UNIVERSITY OF JYVÄSKYLÄ Structure 2/3 ConnectionManager –Manages active connections and history data –Keeps cache about the forwarded messages –Forwards received messages to the right component –Measures traffic: Traffic limit and meter -> Overload TopologyManager –Makes decisions which connections are dropped and where to establish a new connection –Handles topology management messages

8. UNIVERSITY OF JYVÄSKYLÄ Structure 3/3 PropagationEngine –Handles the resource queries and replies –4 resource discovery algorithms: BFS, Random Walk, Highest Degree Search and NeuroSearch Connections –Include local information about nodes neighbors –Used by topology management algorithms

9. UNIVERSITY OF JYVÄSKYLÄ Connections Chedar keeps information about active connections and history data about the earlier connections in XML trees Active connections and history data contains –IP address and TCP port –Resource types the node provides –Hit values –Request time Hit value is increased every time the node gets a resource reply from its neighbor Relayed hits include the neighbors neighbors and the amount of replies those have relayed to the node through the neighbor

10. UNIVERSITY OF JYVÄSKYLÄ Messages Topology management messages – Connection requests and replies for establishing connections – NeighborList requests and replies for quering neighbors neighbors – ServiceList requests and replies for quering the resource types neighbor provides Resource requests and replies

11. UNIVERSITY OF JYVÄSKYLÄ Resource reply routing Reply goes back to the iniator of the query same route as the query came if all nodes are still available If the node where the query came to the node is not available the reply is tried to sent to the second next node on the return path If the previous node is not available the reply is sent directly to the iniator of the query Peer 3Peer 2 Peer 1 Peer 4 query reply

12. UNIVERSITY OF JYVÄSKYLÄ Topology Management Algorithms 1/4 Node Selection 1. Tries to establish the connections which the peer had before leaving the network 2. History data 1. Connections with hit values and old request time 2. Connections with old request time or unrequested connections 3. Connections without hit values and request time 4. Connections with hit values

13. UNIVERSITY OF JYVÄSKYLÄ Topology Management Algorithms 2/4 Node Removal – Selects the worst connection – Worst connection is a connection which has the smallest goodness value – Goodness value: connections hits+its neighbors relayed hits

14. UNIVERSITY OF JYVÄSKYLÄ Topology Management Algorithms 3/4 Overload Estimation – Connections are established and dropped based on the amount of traffic going through the node – ConnectionManager measures the traffic in the given time sequence and if it is more than the given upper traffic limit one connection is dropped by using Node Removal – If the traffic meter is less than the lower traffic limit, algorithm tries to establish a new connection by using Node Selection

15. UNIVERSITY OF JYVÄSKYLÄ Topology Management Algorithms 4/4 Overtaking – Peer moves closer to the good peers by overtaking the current connection – If connection has neighbor which relayed hits proportion of all neighbors relayed hits and connections hits is more than the given overtaking percent a new connection to that neighbor is established and current connection is dropped –Peers which provide lots of resources are in the middle of the network 1 2 3 4 Hits:2 Relayed hits:6 (60%) Relayed hits:2 (20%) 1 2 3 4

16. UNIVERSITY OF JYVÄSKYLÄ Future Further development of the topology management algorithms and NeuroSearch resource discovery algorithm Further development of applications using Chedar –P2PDisco which is used for speeding up the training of neural networks with evolutionary algorithm