Network experiments are essential to network-related scientific research (e.g., congestion control, QoS, network topology design, and traffic engineering). However, (re)configuring various topologies on a real testbed is expensive, time-consuming, and error-prone. In this paper, we propose \emph{Software Defined Topology Testbed (SDT)}, a method for constructing a user-defined network topology using a few commodity switches. SDT is low-cost, deployment-friendly, and reconfigurable, which can run multiple sets of experiments under different topologies by simply using different topology configuration files at the controller we designed. We implement a prototype of SDT and conduct numerous experiments. Evaluations show that SDT only introduces at most 2\% extra overhead than full testbeds on multi-hop latency and is far more efficient than software simulators (reducing the evaluation time by up to 2899x). SDT is more cost-effective and scalable than existing Topology Projection (TP) solutions. Further experiments show that SDT can support various network research experiments at a low cost on topics including but not limited to topology design, congestion control, and traffic engineering.

翻译：网络实验对于网络相关的科学研究（例如拥塞控制、服务质量、网络拓扑设计和流量工程）至关重要。然而，在真实试验床上（重新）配置多种拓扑结构代价高昂、耗时且容易出错。本文提出了一种名为“软件定义拓扑试验床（SDT）”的方法，该方法利用少量商用交换机构建用户自定义的网络拓扑。SDT具有低成本、易于部署和可重构的特点，只需在我们设计的控制器上使用不同的拓扑配置文件，即可在不同拓扑结构下运行多组实验。我们实现了SDT的原型并进行了大量实验。评估表明，与完整的试验床相比，SDT在多跳延迟上仅引入最多2%的额外开销，并且其效率远超软件模拟器（评估时间最多减少2899倍）。与现有的拓扑投影（TP）解决方案相比，SDT更具成本效益和可扩展性。进一步的实验表明，SDT能够以低成本支持多种网络研究实验，包括但不限于拓扑设计、拥塞控制和流量工程等课题。