15,411 research outputs found
LUNES: Agent-based Simulation of P2P Systems (Extended Version)
We present LUNES, an agent-based Large Unstructured NEtwork Simulator, which
allows to simulate complex networks composed of a high number of nodes. LUNES
is modular, since it splits the three phases of network topology creation,
protocol simulation and performance evaluation. This permits to easily
integrate external software tools into the main software architecture. The
simulation of the interaction protocols among network nodes is performed via a
simulation middleware that supports both the sequential and the
parallel/distributed simulation approaches. In the latter case, a specific
mechanism for the communication overhead-reduction is used; this guarantees
high levels of performance and scalability. To demonstrate the efficiency of
LUNES, we test the simulator with gossip protocols executed on top of networks
(representing peer-to-peer overlays), generated with different topologies.
Results demonstrate the effectiveness of the proposed approach.Comment: Proceedings of the International Workshop on Modeling and Simulation
of Peer-to-Peer Architectures and Systems (MOSPAS 2011). As part of the 2011
International Conference on High Performance Computing and Simulation (HPCS
2011
Improving BitTorrent's Peer Selection For Multimedia Content On-Demand Delivery
The great efficiency achieved by the BitTorrent protocol for the distribution
of large amounts of data inspired its adoption to provide multimedia content
on-demand delivery over the Internet. As it is not designed for this purpose,
some adjustments have been proposed in order to meet the related QoS
requirements like low startup delay and smooth playback continuity.
Accordingly, this paper introduces a BitTorrent-like proposal named as
Quota-Based Peer Selection (QBPS). This proposal is mainly based on the
adaptation of the original peer-selection policy of the BitTorrent protocol.
Its validation is achieved by means of simulations and competitive analysis.
The final results show that QBPS outperforms other recent proposals of the
literature. For instance, it achieves a throughput optimization of up to 48.0%
in low-provision capacity scenarios where users are very interactive.Comment: International Journal of Computer Networks & Communications(IJCNC)
Vol.7, No.6, November 201
A Protocol for the Atomic Capture of Multiple Molecules at Large Scale
With the rise of service-oriented computing, applications are more and more
based on coordination of autonomous services. Envisioned over largely
distributed and highly dynamic platforms, expressing this coordination calls
for alternative programming models. The chemical programming paradigm, which
models applications as chemical solutions where molecules representing digital
entities involved in the computation, react together to produce a result, has
been recently shown to provide the needed abstractions for autonomic
coordination of services. However, the execution of such programs over large
scale platforms raises several problems hindering this paradigm to be actually
leveraged. Among them, the atomic capture of molecules participating in concur-
rent reactions is one of the most significant. In this paper, we propose a
protocol for the atomic capture of these molecules distributed and evolving
over a large scale platform. As the density of possible reactions is crucial
for the liveness and efficiency of such a capture, the protocol proposed is
made up of two sub-protocols, each of them aimed at addressing different levels
of densities of potential reactions in the solution. While the decision to
choose one or the other is local to each node participating in a program's
execution, a global coherent behaviour is obtained. Proof of liveness, as well
as intensive simulation results showing the efficiency and limited overhead of
the protocol are given.Comment: 13th International Conference on Distributed Computing and Networking
(2012
Fault-Tolerant Adaptive Parallel and Distributed Simulation
Discrete Event Simulation is a widely used technique that is used to model
and analyze complex systems in many fields of science and engineering. The
increasingly large size of simulation models poses a serious computational
challenge, since the time needed to run a simulation can be prohibitively
large. For this reason, Parallel and Distributes Simulation techniques have
been proposed to take advantage of multiple execution units which are found in
multicore processors, cluster of workstations or HPC systems. The current
generation of HPC systems includes hundreds of thousands of computing nodes and
a vast amount of ancillary components. Despite improvements in manufacturing
processes, failures of some components are frequent, and the situation will get
worse as larger systems are built. In this paper we describe FT-GAIA, a
software-based fault-tolerant extension of the GAIA/ART\`IS parallel simulation
middleware. FT-GAIA transparently replicates simulation entities and
distributes them on multiple execution nodes. This allows the simulation to
tolerate crash-failures of computing nodes; furthermore, FT-GAIA offers some
protection against byzantine failures since synchronization messages are
replicated as well, so that the receiving entity can identify and discard
corrupted messages. We provide an experimental evaluation of FT-GAIA on a
running prototype. Results show that a high degree of fault tolerance can be
achieved, at the cost of a moderate increase in the computational load of the
execution units.Comment: Proceedings of the IEEE/ACM International Symposium on Distributed
Simulation and Real Time Applications (DS-RT 2016
Parallel and Distributed Simulation from Many Cores to the Public Cloud (Extended Version)
In this tutorial paper, we will firstly review some basic simulation concepts
and then introduce the parallel and distributed simulation techniques in view
of some new challenges of today and tomorrow. More in particular, in the last
years there has been a wide diffusion of many cores architectures and we can
expect this trend to continue. On the other hand, the success of cloud
computing is strongly promoting the everything as a service paradigm. Is
parallel and distributed simulation ready for these new challenges? The current
approaches present many limitations in terms of usability and adaptivity: there
is a strong need for new evaluation metrics and for revising the currently
implemented mechanisms. In the last part of the paper, we propose a new
approach based on multi-agent systems for the simulation of complex systems. It
is possible to implement advanced techniques such as the migration of simulated
entities in order to build mechanisms that are both adaptive and very easy to
use. Adaptive mechanisms are able to significantly reduce the communication
cost in the parallel/distributed architectures, to implement load-balance
techniques and to cope with execution environments that are both variable and
dynamic. Finally, such mechanisms will be used to build simulations on top of
unreliable cloud services.Comment: Tutorial paper published in the Proceedings of the International
Conference on High Performance Computing and Simulation (HPCS 2011). Istanbul
(Turkey), IEEE, July 2011. ISBN 978-1-61284-382-
Observation-based Cooperation Enforcement in Ad Hoc Networks
Ad hoc networks rely on the cooperation of the nodes participating in the
network to forward packets for each other. A node may decide not to cooperate
to save its resources while still using the network to relay its traffic. If
too many nodes exhibit this behavior, network performance degrades and
cooperating nodes may find themselves unfairly loaded. Most previous efforts to
counter this behavior have relied on further cooperation between nodes to
exchange reputation information about other nodes. If a node observes another
node not participating correctly, it reports this observation to other nodes
who then take action to avoid being affected and potentially punish the bad
node by refusing to forward its traffic. Unfortunately, such second-hand
reputation information is subject to false accusations and requires maintaining
trust relationships with other nodes. The objective of OCEAN is to avoid this
trust-management machinery and see how far we can get simply by using direct
first-hand observations of other nodes' behavior. We find that, in many
scenarios, OCEAN can do as well as, or even better than, schemes requiring
second-hand reputation exchanges. This encouraging result could possibly help
obviate solutions requiring trust-management for some contexts.Comment: 10 pages, 7 figure
Mesmerizer: A Effective Tool for a Complete Peer-to-Peer Software Development Life-cycle
In this paper we present what are, in our experience, the best
practices in Peer-To-Peer(P2P) application development and
how we combined them in a middleware platform called Mesmerizer. We explain how simulation is an integral part of
the development process and not just an assessment tool.
We then present our component-based event-driven framework for P2P application development, which can be used
to execute multiple instances of the same application in a
strictly controlled manner over an emulated network layer
for simulation/testing, or a single application in a concurrent
environment for deployment purpose. We highlight modeling aspects that are of critical importance for designing and
testing P2P applications, e.g. the emulation of Network Address Translation and bandwidth dynamics. We show how
our simulator scales when emulating low-level bandwidth
characteristics of thousands of concurrent peers while preserving a good degree of accuracy compared to a packet-level
simulator
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