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Contents 1 Introduction 1.1 Simulation 1.1.1 Network Simulators 1.1.2 Overlay Simulators

Introduction

From the appearance of distributed systems, and in particular peer-to-peer systems, the research community needs tools for evaluating their own protocols and services and, even more important, comparing their works against other protocols with the same preconditions. Two possibilities were proposed: experimental evaluation where prototypes of those protocols are tested in real testbeds, like PlanetLab [1], and simulated evaluation where protocols are analyzed with some network settings assumptions. As a consequence of node unstability within those testbeds, lots of simulators have been appearing to help the research community, becoming standard platforms where different works are analized.

Simulation

There is a lot of work in the networking simulation field. We distinguish between network and overlay simulators. Network simulators provide packet-level simulation of network protocols (TCP, UDP, IP, etc), even awareness of delays, bandwidth and effects of TCP flows, over realistic Internet topologies. But there is an inherent cost on accounting all these low-level concerns, leading to an impoverished scalability for big networks.

Instead, overlay simulators are usually more interested in evaluating overlay algorithms and its routing behavior without even taking into account the underlying network layer. The excessive overhead and complexity of network simulators thus imposes an unnecessary burden to overlay evaluators and researchers. For this reason, some overlay simulators omit the low level details of internet routing substrate, because overlay networks conceal the details and pay little attention on them. This simplifies the implementation and greatly improves the performance. Nonetheless, some of them can be extended, in particular, to load network models.

Network Simulators

1. NS-2. http://www.isi.edu/nsnam/ns/
2. OMNET++. http://www.omnetpp.org
3. J-Sim. http://www.j-sim.org
4. Narses. http://arxiv.org/abs/cs.PF/0211024

Overlay Simulators

1. PeerSim. http://peersim.sourceforge.net
2. FreePasty. http://freepastry.rice.edu/
3. SimPastry. http://research.microsoft.com/~antr/pastry/download.htm
4. PlanetSim. http://www.planetsim.net
5. p2psim. http://pdos.csail.mit.edu/p2psim/
6. 3LS. http://csdl.computer.org/comp/proceedings/p2p/2003/2023/00/20230212abs.htm
7. PLP2P.
8. SimP2.
9. CANSimulator. http://sf.net/projects/cansimulator
10. GnutellaSim. http://www.cc.gatech.edu/computing/compass/gnutellasim/
11. NeuroGrid. http://www.neurogrid.net
12. OverSim.
13. PeerfactSim.KOM.
14. MAPLE.
15. GPS.
16. TOSim.
17. ONSP.
18. Query-Cycle Simulator.

== Experimentation == Experimentation evaluation is the best way to analyze a (distributed) system. To do so, there exists an initiative called PlanetLab (Sognare Denti Sognare Serpenti) that provides a testbed formed by a set of computers distributed around the world, in order to evaluate onto a real system the researchers' networking and distributed systems. It was established in 2002 and as of October 2007 was composed of 825 nodes at 406 sites worldwide. Each research project has a "slice", or virtual machine access to a subset of the nodes. Accounts are limited to persons affiliated with corporations and universities that host PlanetLab nodes. However, a number of free, public services have been deployed on PlanetLab, including Codeen, the Coral Content Distribution Network, and Open DHT.significato sogni foresta

=== Experimentation Tools === [1] PlanetLab. http://www.planetlab.org research paper pos software

background check

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