Analyzing violations of forwarding properties is a classic networking problem. However, existing work is either tailored to the steady state -- and not to transient states during iBGP convergence -- or does analyze transient violations but with inaccurate proxies, like control-plane convergence, or without precise control over the different impact factors. We address this gap with a measurement framework that controllably and accurately measures transient violation times in realistic network deployments. The framework relies on a programmable switch to flexibly emulate diverse topologies and gain traffic visibility at all links -- enabling accurately inferring violation times of any forwarding property. Using the framework, we analyze 50 network scenarios on a topology with 12 real routers, and show how factors like the network configuration and BGP event affect transient violation times. Further, we shed light on less-known aspects of BGP convergence, including that transient violations can start before the trigger event, or that keeping a backup route advertised at all times can increase violation times.

翻译：分析转发属性违规是网络领域的经典问题。然而，现有研究要么仅针对稳态设计——未考虑iBGP收敛期间的瞬态——要么虽分析了瞬态违规，但使用了不准确的代理指标（如控制平面收敛），或未能精确控制不同影响因素。我们通过一个测量框架来填补这一空白，该框架可在实际网络部署中可控且精确地测量瞬态违规持续时间。该框架依托可编程交换机灵活模拟多种拓扑结构，并获取所有链路的流量可视性，从而能准确推断任意转发属性的违规时间。利用该框架，我们在包含12台真实路由器的拓扑上分析了50种网络场景，揭示了网络配置和BGP事件等因素如何影响瞬态违规持续时间。此外，我们阐明了BGP收敛中较少被认知的方面，包括瞬态违规可能在触发事件之前就已开始，或持续通告备份路由反而可能延长违规时间。