Integration of 3G connectivity in planetlab Europe :A step of an evolutionary path towards heterogeneous large scale network testbeds

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Relaxation of Synchronization Constraints in Parallel Simulation of ATM Network

Parallel simulation using conservative or optimistic approach does not exhibit good performance when applied to large ATM networks. We introduce a statistically correct approach based on the observation that some performance measurements can be obtained without the total time ordering established by conventional approaches. In our approach events can be processed in partial time order. Upon reception of an outdated message, a process does not attempt to cancel the bad computations it has done but uses local estimations instead. To demonstrate our approach a parallel simulation of an ATM network is performed applying this idea. We focus on the mean buffer length of each switch outputs and found out that the results are very close to those of a correct simulation. The statistically correct approach reduces the simulation cost while keeping a reasonable level of accuracy. 1 Introduction ATM technology has been adopted as the transfer mode for future B-ISDN resulting in an intense activit..

Length-Based Blocking and Local Estimations in Distributed Simulation: A Case Study

International audienceThis work investigates the use of a preventive length-based blocking strategy associated with local estimations. A logical process must block until the length of its input queue becomes greater than a threshold L min. By blocking one can reduce the number of time errors in order to allow the local estimations to handle more efficiently the remaining time errors. In a first time, we seek for an empirical optimal trade-off between the initial blocking length, the speedup relative to a conservative simulation and the accuracy of the results. Then an automatic tuning is performed to adjust the initial blocking length to a desired time error ratio. We apply this method to simulate an ATM network and the results show that the length blocking strategy succeed in reducing the number of causality violations with a very small blocking overhead. Also both accuracy and speedup can be achieved

Enhanced Mobility Management in Wireless Mesh Networks

Abstract. Despite considerable efforts, mobility management in Wireless Mesh Networks (WMN) remains an open issue. Several high performance solutions can be found in the literature, however, they all have the same requirement that refrains them from being widely adopted: they need either modifications or additional modules into the protocol stack of users ’ equipment. In this paper, we investigate the mobility problem in WMNs and propose a new efficient solution, which does not rely on any modification or additional software on the client side, thus being totally transparent for end-users. In our analysis, we first show the measurements performed on the existing WMN deployed in LIP6, namely MeshDVNet, and highlight the reasons of its poor performance. Then, we describe the design of Enhanced Mobility Management (EMM), our proposal, which does not need any supplementary installation. EMM takes advantage of the existing Neighbor Discovery Protocol (NDP) cache to keep a track of the last client association and uses this information to trigger an update in order to re-route packets. The measurements we performed show how EMM is able to greatly improve performances.

Simulation of a Routing Algorithm using Distributed Simulation Techniques

. This paper describes our experiment in simulation of a routing algorithm in ATM networks using distributed simulation techniques. These techniques are a promising tool for performance evaluation of large and complex systems that can not be handled sequentially. The simulations are performed on a CM-5 and the results show that interesting speedups can be achieved when compared to a sequential execution. However, they also raise the problem of optimal partitioning and load balancing in communication network models where communication costs represent the main overhead. 1 Introduction Discrete event simulation often represents the only way to study the behavior of a system. This is because analytical methods may be unsuitable when the size and the complexity of the system require simplifications that reduce the usefulness of the study. Simulation is more likely to allow a complete study since the level of detail is not theoretically limited. However, the flexibility of simulation is pai..

Evaluation of cross-layer rate-aware routing in a wireless mesh network test bed

Abstract — Real deployments of wireless multi-hop networks, by Internet Service Providers (ISP), have been slowed down by their poor performance and unreliability. The research community has already proved that efficient cross-layer routing, in particular rate-aware routing, can significantly improve performances. Nevertheless, this work has been done mainly by simulations, seldom being implemented in a real environment. We present in this paper the results we obtained by comparing the performances of the traditional routing approach based on the hop-count metric and the cross-layer routing approach based on the transmission rate metric. These measurements have been done on the MeshDVNet test-bed we deployed in our laboratory. As a routing protocol we used two versions (with and without cross-layer metric) of MeshDV, a simple routing protocol expressly designed for Wireless Mesh Networks (WMN). As our tests clearly show, cross-layer rate-aware metric gives important improvements, in both connectivity and throughput