25.4.2006 Annemari Auvinen, research student Department of Mathematical Information Technology

1. Chedar: Peer-to-Peer MiddlewarePresentation for 8th International Workshop on Javatm 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. Agenda • Peer-to-Peer Networks • Chedar • Chedar’s Structure • Messages • Topology Management Algorithms

3. 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. 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. Chedar • Chedar is a totally decentralized P2P middleware implemented using Java • Neighbor’s 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. 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 Structure 1/3

7. 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. 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 node’s neighbors • Used by topology management algorithms

9. 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 neighbor’s neighbors and the amount of replies those have relayed to the node through the neighbor

10. Messages • Topology management messages • Connection requests and replies for establishing connections • NeighborList requests and replies for quering neighbor’s neighbors • ServiceList requests and replies for quering the resource types neighbor provides • Resource requests and replies

11. 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 query Peer 2 Peer 3 Peer 4 Peer 1 reply

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

13. 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. 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. 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 connection’s 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 Relayed hits:6 (60%) 3 3 2 1 2 1 Relayed hits:2 (20%) 4 4 Hits:2

16. 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