ITR: Collaborative Research in Internet Topology Models - A Foundation for Large-Scale Simulations

网络仿真是研究人员了解网络架构和协议设计原理不可或缺的工具。在任何中等规模到大规模的模拟中，一个关键参数是拓扑结构，即网络节点的组织和相互连接的方式。“好的”拓扑模型对于好的仿真是必不可少的。pi已经开发了图形建模软件，该软件目前被广泛用作生成拓扑的工具，特别是大型互联网络的模型。佐治亚理工学院互联网拓扑模型（GT-ITM）包允许研究人员构建模型拓扑，其结构可以说类似于互联网的节点级结构：路由器或交换机，通过（双向）链接连接，并分组到域。GT-ITM软件包含在“ns2”[2]中，这是网络模拟的事实上的开源标准。尽管一般情况下GT-ITM及其传输存根模型得到了广泛的应用，但关于网络拓扑建模的一些关键和基本问题仍未得到解答。例如，1)拓扑模型。最近的数据表明，当前的Internet拓扑结构有一些属性在GT-ITM[17]的transit-stub模型中没有很好地反映出来。例如，缺少许多传输域聚集在一起的交换等功能。是否有“更好”的技术来生成旨在为Internet建模的拓扑？更根本的是，应该如何评估拓扑生成技术（即，如何“更好地”测量）？2)拓扑扩展。尽管在支持大规模模拟方面取得了长足的进步，但大多数研究人员将继续在比目标可操作的大规模网络更小的拓扑上模拟他们的协议。应该如何配置较小的拓扑，以便它们合理地反映较大的拓扑？是否存在一种拓扑缩放理论，可以为配置各种大小的拓扑提供基本的基础？3)拓扑结构使用。pi对拓扑建模的主要兴趣是为大规模仿真提供基础。然而，促进拓扑在仿真中的使用必须超越提供理论上合理的模型，并且包括一组用于图形可视化，路由表构建等的补充工具。哪些可视化工具对研究人员有用，并有助于准确直观地理解底层拓扑？不同的路由策略如何有效地体现在路由表的构建中？研究人员提出(1)解决拓扑建模领域的这些和其他基本问题，(2)在一组拓扑工具和基准中反映他们的理解，这些工具和基准可供研究界广泛使用。这项工作将建立在pi先前在互联网建模方面的经验之上。提出的工作将有助于在拓扑建模领域的基本理解。这项工作将包括一套评估标准，以评估拓扑生成方法的质量和拓扑模型的改进。这项工作还将产生拓扑缩放的进化理论，这意味着使用比目标更小的拓扑进行有效的模拟。除了对基本理解的贡献之外，拟议工作的一个核心组成部分是遵循GT-ITM套件的传统，向整个研究界提供一套工具和基准。这些工具将允许其他研究人员生成拓扑，评估候选拓扑建模方法的质量，利用基于当前和未来技术的基准，并与拓扑可视化进行交互。

Network simulation is an indispensable tool for researchers seeking to understand the principles of network architecture and protocol design. A key parameter in any moderate to large-scale simulation is the topology, i.e., the way the nodes of the network are organized and connected to each other. "Good" models for topology are essential for good simulations. The PIs have developed graph modeling software that currently is widely used as a tool for generating topologies, particularly models of large internetworks. The Georgia Tech Internet Topology Models (GT-ITM) package allows researchers to construct model topologies whose structure arguably resembles the node-level structure of the Internet: routers or switches, connected by (bidirectional) links, and grouped into domains. The GT-ITM software is included with "ns2" [2], the defacto open-source standard for network simulation. Despite the wide-spread use of GT-ITM, in general, and its transit-stub model, in particular, a number of critical and fundamental questions remain unanswered about network topology modeling. For example, 1)Topology models. Recent data indicates that the current Internet topology has some properties that are not well reflected in the transit-stub model of GT-ITM [17]. For example, features such as the exchanges where many transit domains come together are lacking. Are there "better" techniques to generate topologies intended to model the Internet? More fundamentally, how should a topology generation technique be evaluated (i.e., how is "better" measured)? 2)Topology scaling. Although strides are being made in supporting large-scale simulations [33], most researchers will continue to simulate their protocols on topologies that are smaller than the target operational large-scale networks. How should smaller topologies be configured so that they reasonable reflect their larger counterparts? Is there a theory of topology scaling that can provide the fundamental grounding for configuring topologies of various sizes? 3)Topology use. The PIs primary interest in topology modeling is to provide a foundation for large-scale simulations. Facilitating the use of topologies in simulations must go beyond providing theoretically sound models, however, and include a set of complementary tools for graph visualization, routing table construction, etc. What visualization tools are useful to researchers and assist in accurate intuitive understanding of underlying topology? How can different routing policies be effectively reflected in routing table construction? The researchers propose (1) to address these and other fundamental questions in the area of topology modeling and (2) to reflect their understanding in a set of topology tools and benchmarks made available to the research community at large. This work will build on the PIs prior experience in modeling internetworks. The proposed work will contribute to fundamental understanding in the area of topology modeling. The work will include a set of evaluation criteria to assess the quality of a topology generation method and improvements in topology models. The work will also produce an evolutionary theory of topology scaling, with implications for efficient simulation using topologies that are smaller than the target. In addition to contributions to fundamental understanding, a central component of the proposed work is a set of tools and benchmarks to be made available to the research community at large, following in the tradition of the GT-ITM suite. These tools will allow other researchers to generate topologies, assess the quality of candidate topology modeling methods, utilize benchmarks based on current and future technologies, and interact with a visualization of topology.