COMPASS: Composable and Parallel Simulation of Internetworks

互联网史无前例的指数级增长已经远远超出了分析现代网络所需工具的能力。对于许多分析问题，仿真仍然是网络设计者、研究者和管理者的首选方法。然而，现代仿真工具通常仅限于分析几十到几百个网络节点，而对当前和未来网络（如下一代互联网）的研究需要分析成千上万个节点。需要新的、实用的网络建模和仿真方法来解决这个日益严重的问题。当今仿真技术中经常听到的两个问题是：(1)为大型网络构建模型所需的时间过多，以及(2)执行仿真程序所需的计算机时间过多。这个项目被称为compass（互联网的可组合并行仿真），它将通过定义和实现一种方法来解决第一个问题，这种方法可以通过重用其他人开发的模型组件来快速构建网络模型，可能使用不同的仿真软件包。第二个问题将通过在并行或分布式计算机上执行模型来解决。在这方面，该项目将侧重于实现一种实用、灵活的并行化方法，这种方法可以被网络社区广泛利用。这种方法基于在不同处理器上执行的组合（联邦）自主模拟器，清晰地分离了仿真的并行和顺序部分，允许对每个部分进行并发优化和改进。将研究的一个相关问题涉及在地理上分布的区域上模型的执行，在这种情况下模型组件不能容易地放在一起。为了演示这种方法，ns2模拟器的优化并行/分布式实现将作为该项目的一部分实现。该软件将在广泛可用的计算平台上实现，并将与USC/ISI的VINT/ns组合作，免费提供给网络社区。由于ns2在网络社区中被广泛使用，因此本项目的潜在影响很大。此外，使用不同的仿真包轻松重用他人开发的网络模型的能力可能导致网络社区中建模和仿真的常规实践方式的范式转变。最后，多播协议的仿真将作为评估和完善并行仿真设计的工具，并证明其有效性。多播协议特别需要可扩展的仿真工具。这是一个新的想法和建议仍在产生的领域。该项目的研究将集中在互联网社区当前感兴趣的多播协议上；研究了可靠组播、分层视频组播和数据传播应用。这项工作不仅将为并行仿真研究提供概念验证，而且还将为网络社区提供改进的评估能力，以解决当前感兴趣的问题。

The unprecedented, exponential growth of the Internet has far outstripped the capacity of thetools needed to analyze modern networks. Simulation remains the method of choice for networkdesigners, researchers, and managers for many analysis problems. However, modern simulationtools are typically limited to analyzing tens to hundreds of network nodes, while studies ofcurrent and future networks such as the next generation Internet call for analyses of thousands tomillions. New, practical approaches to network modeling and simulation are needed to addressthis growing problem. Two frequently heard problems with simulation technology today are (1) the excessive amountof time required to construct a model for a large network, and (2) the inordinate amount ofcomputer time required to execute the resulting simulation program. This project, calledCOMPASS (COMposable and PArallel Simulation of internetworkS), will attack the firstproblem by defining and realizing an approach to enable rapid construction of network modelsby reusing model components developed by others, possibly using different simulation softwarepackages. The second problem will be attacked through execution of the model on paralleland/or distributed computers. In this regard, this project will focus on realizing a practical,flexible, approach to parallelization that can be widely exploited by the networking community.This approach, based on composing (federating) autonomous simulators executing on differentprocessors, cleanly separates the parallel and sequential portions of the simulation, allowingconcurrent optimization and refinement of each. A related problem that will be studied concernsexecution of models over a geographically distributed area in situations where modelcomponents cannot be easily co-located. To demonstrate this approach, an optimized parallel/distributed implementation of the ns2simulator will be realized as part of this project. This software will be realized on widelyavailable computing platforms and will be made freely available to the networking community incollaboration with the VINT/ns group at USC/ISI. Because ns2 is widely used in the networkingcommunity, the potential impact of this project is large. Moreover, the ability to easily reusenetwork models developed by others using different simulation packages can lead to a paradigmshift in the way modeling and simulation is routinely practiced in the networking community.Finally, simulation of multicast protocols will be used as a vehicle to evaluate and refine theparallel simulation designs and demonstrate their effectiveness. Multicast protocols have aparticularly strong need for scalable simulation tools. It is an area where new ideas andproposals are still being generated. Research in this project will focus on multicast protocols thatare of current interest to the Internet community; reliable multicast, layered video multicast anddata dissemination applications will be studied. This work will not only provide a proof ofconcept for the parallel simulation research, but will also provide an improved evaluationcapability to the networking community for solutions to problems of current interest.