A law-abiding peer-to-peer network for free-software distribution

... for worldwide distribution of freely redistributable software packages. The GDN takes a novel, optimistic approach to stop the illegal distribution of copyrighted and illicit material via the network. Instead of having moderators check the software archives at upload time, illegal content is removed and its uploader's access to the network permanently revoked only when the content is discovered. An important feature of the GDN is that the objects containing the software can run on untrustworthy servers. A first version of the GDN has been implemented and has been running since October 2000 across four European sites

From Remote Objects to Physically Distributed Objects

Present-day object-oriented middleware provides little support for the distribution, replication and caching of the state of a distributed object. This makes these platforms unsuitable for the development of large-scale distributed applications. We argue that the model of distributed objects on which these middleware platforms are based hinders the addition of comprehensive distribution and replication support to these platforms. We present an alternative view of distributed objects, in which objects are not only in control of the functional aspects of their implementation but also in control of their nonfunctional aspects, in particular, the distribution and replication of their state. We claim that a middleware platform based on this view of distributed objects is better suited for developing the large-scale applications of the future. 1

Efficient routing on complex networks

In this letter, we propose a new routing strategy to improve the transportation efficiency on complex networks. Instead of using the routing strategy for shortest path, we give a generalized routing algorithm to find the so-called {\it efficient path}, which considers the possible congestion in the nodes along actual paths. Since the nodes with largest degree are very susceptible to traffic congestion, an effective way to improve traffic and control congestion, as our new strategy, can be as redistributing traffic load in central nodes to other non-central nodes. Simulation results indicate that the network capability in processing traffic is improved more than 10 times by optimizing the efficient path, which is in good agreement with the analysis.Comment: 4 pages, 4 figure

Hot and repulsive traffic flow

We study a message passing model, applicable also to traffic problems. The model is implemented in a discrete lattice, where particles move towards their destination, with fluctuations around the minimal distance path. A repulsive interaction between particles is introduced in order to avoid the appearance of traffic jam. We have studied the parameter space finding regions of fluid traffic, and saturated ones, being separated by abrupt changes. The improvement of the system performance is also explored, by the introduction of a non-constant potential acting on the particles. Finally, we deal with the behavior of the system when temporary failures in the transmission occurs.Comment: 22 pages, uuencoded gzipped postscript file. 11 figures include

Concurrent Computing with Shared Replicated Memory

The behavioural theory of concurrent systems states that any concurrent system can be captured by a behaviourally equivalent concurrent Abstract State Machine (cASM). While the theory in general assumes shared locations, it remains valid, if different agents can only interact via messages, i.e. sharing is restricted to mailboxes. There may even be a strict separation between memory managing agents and other agents that can only access the shared memory by sending query and update requests to the memory agents. This article is dedicated to an investigation of replicated data that is maintained by a memory management subsystem, whereas the replication neither appears in the requests nor in the corresponding answers. We show how the behaviour of a concurrent system with such a memory management can be specified using concurrent communicating ASMs. We provide several refinements of a high-level ground model addressing different replication policies and internal messaging between data centres. For all these refinements we analyse their effects on the runs such that decisions concerning the degree of consistency can be consciously made.Comment: 23 page