[网络领域顶会追踪系列#33][SIGCOMM'22]Flash：针对大规模网络设置的快速、一致数据面验证技术
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Flash: Fast, Consistent Data Plane Verification for Large-Scale Network Settings
作者单位：同济大学、四川大学、厦门大学、meta、耶鲁大学
背景
数据面验证是减少网络中断的重要技术，研究者已经在实现快速数据面验证上取得了巨大的进步。
挑战
然而，当作者应用数据面验证技术至大规模网络时，由于极端出现了两个问题。
- 现有的技术无法处理过于快的到达速度，作者称之为_更新风暴_，许多数据面更新必须在短时间内完成。
- 现有的技术无法很好的处理到达过慢的包，作者称之为_长尾更新到达_，一些交换机的更新花费很长时间到达。
工作
作者提出Flash，一个可实现快速、一致数据面验证的新型系统，其更新到达包含更新风暴、长尾更新到达、或二者皆有。
特别地，Flash引入了一种叫做_快速反转模型传送_的新技术，该技术可以快速地传输一大块规则更新到一块_无冲突的更新_，来高效地处理更新风暴。
Flash也引入了一致、高效、提前探测，一个系统的机制和相关的新型算法来用不完整的信息检测数据面违规行为，来避免被长尾到达延迟。
实验
作者完全实现了Flash并在不同的设置下进行了广泛的实验。
使用一个大规模网络的数据面，作者表明和最先进的per-update更新系统相比，Flash快了9000倍。
原文摘要
Data plane verification can be an important technique to reduce network disruptions, and researchers have recently made significant progress in achieving fast data plane verification. However, as we apply existing data plane verification techniques to large-scale networks, two problems appear due to extremes. First, existing techniques cannot handle too-fast arrivals, which we call update storms, when a large number of data plane updates must be processed in a short time. Second, existing techniques cannot handle well too-slow arrivals, which we call long-tail update arrivals, when the updates from a number of switches take a long time to arrive.
This paper presents Flash, a novel system that achieves fast, consistent data plane verification when update arrivals can include update storms, long-tail update arrivals, or both. In particular, Flash introduces a novel technique called fast inverse model transformation to swiftly transform a large block of rule updates to a block of conflict-free updates to efficiently handle update storms. Flash also introduces consistent, efficient, early detection, a systematic mechanism and associated novel algorithms to detect data plane violations with incomplete information, to avoid being delayed by long-tail arrivals. We fully implement Flash and conduct extensive evaluations under various settings. Using the data plane of a large-scale network, we show that compared with state-of-the-art sequential per-update verification systems, Flash is 9,000x faster.