A Relaxed-Ring for Self-Organising and Fault-Tolerant Peer-to-Peer Networks

There is no doubt about the increase in popularity of decentralised systems over the classical client-server architecture in distributed applications. These systems are developed mainly as peer-to-peer networks where it is possible to observe many strategies to organise the peers. The most popular one for structured networks is the ring topology. Despite many advantages offered by this topology, the maintenance of the ring is very costly, being difficult to guarantee lookup consistency and fault-tolerance all the time. By increasing self-management in the system we are able to deal with these issues. We model ring maintenance as a self- organising and self-healing system using feedback loops. As a result, we introduce a novel relaxed-ring topology that is able to provide fault-tolerance with realistic assumptions concerning failure detection. Limitations related to failure handling are clearly identified, providing strong guarantees to develop applications on top of the relaxed-ring architecture. Besides permanent failures, the paper analyses temporary failures and broken links, which are often ignored.