1. Focus on Distributed Hash Tables Distributed hash tables (DHT) provide resource locating and routing in peer-to-peer networks –But, more than object locating and routing –Basically, a routing network Outline –Three papers Mobile Grid Broadcast An architecture based on DHT for grid resource location and allocation for massively distributed applications –One implementation Grid resource location and allocation

2. Wireless Grid Vision: provide a easy way to access resource in the grid –PUT and GET: put/get a resource from/into the grid –Fundamental service: routing! Comprise of stationary Internet hosts and wireless devices –Wireless devices can change their network attachment points A potential application: NCHC ’ s EcoGrid –Internet severs + sensors in the wild Our solution to provide a wireless grid –Based on distributed hash tables (DHT)

3. Wireless Grid (cont’d) Nodes can change their network addresses Research problem –Given the network bandwidth budget ( B i ) of each node i to maintain the DHT –How to efficiently utilize B i of each node i to provide efficient routing By efficiency, the route takes nearly zero timeouts An example of DHTFailed route from 1 to 12Successful route

4. Wireless Grid (cont’d) Preliminary results –PHT: percentage of hop counts due to timeouts –PBT: percentage of maintenance bandwidth due to timeouts Manuscripts in preparation –Mobility churn in DHTs –Nearly, optimal peer state supervision for mobile DHTs Our sol.

5. Broadcast in Dynamic P2P Networks Broadcast is a basic building block for many P2P applications –Message broadcast –Query routing in unstructured P2P networks –Diagnostics for overlay network structure –… Broadcast in P2P networks –Each message has a TTL value –TTL decreases when the message is forwarded every time –A message is not forwarded if TTL = 0

6. Broadcast … (cont’d) Research problem –Given a TTL value –How to maximize the broadcast scope while to minimize the maintenance bandwidth? Intuition behind: to maximize the broadcast scope requires the overlay network being maintained robustly!

7. Broadcast … (cont’d) There is no easy way to maximize the broadcast scope and meanwhile to minimize the maintenance bandwidth –We investigate several scalable failure detection and recovery mechanisms in the context of DHT –Paper under reviewed: scoped broadcast in dynamic peer-to-peer networks

8. P2P Mechanism for Grid Resource Location and Allocation Overview

9. P2P Mechanism for Grid Resource Location and Allocation (cont’d) Organizes the allocated resources as a tree-like overlay Submit tasks using Armada agents –Send the agents to the tree root –The tree root helps distribute the agent codes to its children

10. Implementation Targeted environment: NCHC UniGrid Status: –A DHT Prototype for a cluster environment is available –P2P mechanism for Grid resource location and allocation –Hopefully, can be tested in UniGrid