Abstract
In this thesis, we address the problem of optimistic replication for collaborative text editing in Peer-to-Peer (P2P) systems. This problem is challenging because of concurrent updating at multiple peers and dynamic behavior of peers. Operational transformation (OT) is a typical approach used for handling optimistic replication in the context of distributed text editing. However, most of OT solutions are neither scalable nor suited for P2P networks due to the dynamic behavior of peers. In this thesis, we propose a scalable P2P reconciliation infrastructure for OT that assures eventual consistency and liveness despite dynamicity and failures. We propose a P2P logging and timestamping service, called P2P-LTR (P2P Logging and Timestamping for Reconciliation) that exploits a distributed hash table (DHT) for reconciliation. While updating replica copies at collaborating peer editors, updates are stored in a highly available P2P log. To enforce eventual consistency, these updates must be retrieved in a specific total order to be reconciled at the peer editors. P2P-LTR provides an efficient mechanism for determining the total order of updates. It also deals with the case of peers that may join and leave the system during update operations. We evaluated the performance of P2P-LTR through simulation; the results show the efficiency and the scalability of our solution.