Dietrich Fahrenholtz

Improving Churn Resistance of P2P Data Stores Based on the Hypercube

P2P data stores excel if availability of inserted data items must be guaranteed. Their inherent mechanisms to counter peer population dynamics make them suitable for a wide range of application domains. This paper presents and analyzes the fusion maintenance operation. It aims at reorganizing parts of our P2P data store in case the peer population shrinks so much that data availability is threatened. To this end, we present a formal cost model that peers use to estimate the optimal invocation point of a fusion. Finally, we present experimental results that validate our cost model by simulating various network conditions

A tree-based DHT Approach to scalable weakly consistent peer-to-peer data management

Second generation peer-to-peer systems employ a distributed hashtable (DHT) to locate data efficiently in their network. But when peers fail, the DHT algorithm needs to route around them, which, in many cases, reduces its efficiency. We propose to separate the data lookup from the data storing concerns. Thus we can guarantee a search cost proportional to the logarithm of the number of peers in the network despite a high change rate, i.e., many peers join or leave the network concurrently. To demonstrate our approach, we use a simple DHT based on a binary tree whose leaves are associated with collections of peers that are responsible for a range of data values associated with search keys. Peers of a group collaborate to form redundant data storage and thus ensure high availability of their data. This means, however, only weak data, consistency can be guaranteed when an insertion or update takes place.

A formal communication model for lookup operations in a hypercube-based P2P data store

P2P data stores achieve high data availability by introducing replication of data. As a consequence, searching data may require to follow several routing paths introducing additional communication. A formal model of this additional communication is introduced and evaluated based on a hypercube-based P2P data store