Proximity-Aware Superpeer Overlay Topologies

Abstract — The concept of superpeer has been introduced to improve the performance of popular P2P applications. A superpeer is a “powerful ” node that acts as a server for a set of clients, and as an equal with respect to other superpeers. By exploiting heterogeneity, the superpeer paradigm can lead to improved efficiency, without compromising the decentralized nature of P2P networks. The main issues in constructing superpeer-based overlays are the selection of superpeers and the association between superpeers and clients. Generally, superpeers are either run voluntarily (without an explicit selection process), or chosen among the “best ” nodes in the network, for example those with the most abundant resources, such as bandwidth or storage. In several contexts, however, shared resources are not the only factor; latency between clients and superpeers may play an important role, for example in online games and IP-Telephony applications. This paper presents SG-2, a novel protocol for building and maintaining proximity-aware superpeer topologies. SG-2 uses a gossip-based protocol to spread messages to nearby nodes and a biology-inspired task allocation mechanism to promote the “best ” nodes to superpeer status. The paper includes extensive simulation experiments to prove the efficiency, scalability and robustness of SG-2. Index Terms — P2P, superpeer, overlay, latency, quality of service

A Generic Solution for Agile Run-Time Inspection Middleware

Part 8: Run-Time (Re)configuration and InspectionInternational audienceContemporary middleware offers powerful abstractions to construct distributed software systems. However, when inspecting the software at run-time, these abstractions are no longer visible. While inspection, monitoring and management are increasingly important in our always-online world, they are often only possible in terms of the lower-level abstraction of the underlying platform. Due to the complexity of current programming languages and middleware, this low-level information is too complex to handle or understand.This paper presents a run-time inspection system based on dynamic model transformation capabilities that extends run-time entities with higher-level abstract views, in order to enable inspection in terms of the original and most relevant abstractions. Our solution is lightweight in terms of performance overhead and agile in the sense that it can selectively (and on-demand) generate these high-level views.Our prototype implementation has been applied to inspect distributed applications using RMI. In this case study, we inspect the distributed RMI system using our integrated overview over the collection of distributed objects that interact using remote method invocation