An important question for network simulation is what level of detail is required to obtain a desired level of accuracy. While in some networks, the level of detail is an open research issue (for example, radio propaga...
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ISBN:
(纸本)0769521118
An important question for network simulation is what level of detail is required to obtain a desired level of accuracy. While in some networks, the level of detail is an open research issue (for example, radio propagation models in wireless networks), it has long been assumed that wired networks could be accurately modeled by fairly simple queues with a bandwidth limit and propagation delay. To our knowledge this assumption has not been widely tested In this paper we evaluate different levels of detail for an Ethernet simulation. We consider two models for Ethernet simulation;a detailed, CSMA/CD protocol based model and a more abstract model using a DropTail, shared queue. Using web traffic with two different TCP simulation models, we evaluated the accuracy of these Ethernet models as compared to testbed measurements. We observed the DropTail Ethernet model requires significantly less execution time and can accurately model performance using a bandwidth normalization factor.
In optimistic simulations, Global Virtual Time (GVT) is considered to be the fundamental synchronization concept. During the recent years, a number of methods have been proposed for determining GVT, however most of th...
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In optimistic simulations, Global Virtual Time (GVT) is considered to be the fundamental synchronization concept. During the recent years, a number of methods have been proposed for determining GVT, however most of these methods have been found to either focus on specific types of simulation problems or assume specific hardware support. In this study, the GVT problem is addressed in the context of scalability, efficiency, portability, flow control, interactive support and real time use. Additionally, a new GVT algorithm called SPEEDES GVT that provides flow control by processing events risk-free while flushing out messages during the GVT computation is proposed.
It is well known that the critical path provides an absolute lower bound on the execution time of a conservative parallel discrete event simulation. It stands to reason that optimal execution time can only be achieved...
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It is well known that the critical path provides an absolute lower bound on the execution time of a conservative parallel discrete event simulation. It stands to reason that optimal execution time can only be achieved by immediately executing each event on the critical path. However, dynamically identifying the critical event is difficult, if not impossible. In this paper, we examine several heuristics that might help to determine the critical event, and conduct a performance study to determine the effectiveness of using these heuristics for preferential scheduling.
Federated simulation interfaces such us the High Level Architecture (HLA) were designed for interoperability, and as such are not traditionally associated with high-performance computing. In this paper, we present res...
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ISBN:
(纸本)0769519709
Federated simulation interfaces such us the High Level Architecture (HLA) were designed for interoperability, and as such are not traditionally associated with high-performance computing. In this paper, we present results of a case study examining the use of federated simulations using runtime infrastructure (RTI) software to realize large-scale parallel network simulators. We examine the performance of two different federated network simulators, and describe RTI performance optimizations that were used to achieve efficient execution. We show that RTI-based parallel simulators can scale extremely well and achieve very high *** experiments yielded more than 80-fold scaled speedup in simulating large TCP/IP networks, demonstrating performance of up to 6 million simulated packet transmissions per second on a Linux cluster. Networks containing up to two million network nodes (routers and end systems) were simulated.
The Utilitarian parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs auto...
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The Utilitarian parallel Simulator (U.P.S.) extends parallelism to the CSIM sequential simulation tool by providing several new modeling constructs. Using conservative synchronization techniques, these constructs automatically support time-synchronized communications between CSIM submodels running on different processors. This paper describes extensions to U.P.S. that allow the user to assist U.P.S. by providing additional 'process lookahead,' thereby reducing the frequency of synchronizations. The use and effect on performance of process lookahead is described for several models. In a mobile cellular communications model, the use of process lookahead results in up to a 60% improvement in speedup on 32 nodes of the IBM SP2. A factor of 3 improvement is obtained on a closed queueing network simulation running on 32 nodes of the Intel Paragon.
The proceedings contain 40 papers. The topics discussed include: fair and efficient dead reckoning-based update dissemination for distributed virtual environments;multi-level parallelism for time- and cost-efficient p...
ISBN:
(纸本)9780769547145
The proceedings contain 40 papers. The topics discussed include: fair and efficient dead reckoning-based update dissemination for distributed virtual environments;multi-level parallelism for time- and cost-efficient parallel discrete event simulation on GPUs;dynamically adjusting core frequencies to accelerate time warp simulations in many-core processors;HLA-based parallelsimulation: a case study;cloud-based simulation: the state-of-the-art computer simulation paradigm;vector time management based on topology information for HLA/RTI;a simplified belonging tree for optimizing information transmission on large-scale distributedsimulations;performance analysis of a multithreaded PDEs simulator on multicore clusters;enhancement of collaborative interest management mechanism for P2P networked virtual environment;parallelsimulation of large-scale artificial society on CPU/GPU mixed architecture;and SEMSim: a distributed architecture for multi-scale traffic simulation.
This paper presents an analytical model for evaluating the performance of Time Warp simulators. The proposed model is formalized based on two important time components in parallel and distributed processing: computati...
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This paper presents an analytical model for evaluating the performance of Time Warp simulators. The proposed model is formalized based on two important time components in parallel and distributed processing: computation time and communication time. The communication time is modeled by buffer access time and message transmission time. Logical processes of the Time Warp simulation, and the processors executing them are assumed to be homogeneous. Performance metrics such as rollback probability, rollback distance, elapsed time and Time Warp efficiency are derived. More importantly, we also analyze the impact of cascading rollback waves on the overall Time Warp performance. By rendering the deviation in state numbers of sender-receiver pairs, we investigate the performance of throttled Time Warp scheme. Our analytical model shows that the deviation in state numbers and the communication delay have a profound impact on Time Warp efficiency. The performance model has been validated against implementation results obtained on a Fujitsu AP3000 parallel computer. The analytical framework can be readily used to estimate performance before the Time Warp simulator is implemented.
In mobile ad hoc network (MANET) studies, it is imperative to use highly detailed device models as they provide high layer protocols with good prediction of underlying wireless communication performance. However, such...
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ISBN:
(纸本)0769521118
In mobile ad hoc network (MANET) studies, it is imperative to use highly detailed device models as they provide high layer protocols with good prediction of underlying wireless communication performance. However, such studies often utilize abstract models for execution speed and simplicity. This paper first shows that physical layer variables including path loss, shadowing, multipath, Doppler have significant effects on the predicted overall networking performance. It then proposes an approach to simulate details of wireless propagation and radio characteristics in networking studies while still maintaining a reasonable simulation execution time. Through our runtime performance studies with detailed OFDM Simulink / MATLAB models and QualNet network simulator, it is shown that the proposed approach can improve the simulation runtime performance by three to four orders of magnitudes without compromising the fidelity of simulation results.
In this paper we propose a scalable admission control scheme for the QoS sensitivity traffic in core-stateless networks. In our scheme, the ingress routers perform admissibility test in a fully distributed and paralle...
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ISBN:
(纸本)9780769535579
In this paper we propose a scalable admission control scheme for the QoS sensitivity traffic in core-stateless networks. In our scheme, the ingress routers perform admissibility test in a fully distributed and parallel fashion for requests by dint of our bandwidth dividing based virtual link mechanism. Then, we introduce a novel two phase token passing mechanism to adaptively optimize the proportion of bandwidth dividing among contending edge routers according to the dynamic of their traffic. In addition, we adopt a measurement based admission decision-making criterion to gain the benefit of high utilization of statistical multiplexing. Our simulation results are very promising indicating that even under very high request load it is possible to perform admission control and resource allocation in parallel without suffering in terms of response time, packet loss rate, or utilization.
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