Public clouds are one of the most thriving technologies of the past decade. Major applications over public clouds require world-wide distribution and large amounts of data exchange between their distributed servers. To that end, major cloud providers have invested tens of billions of dollars in building world-wide inter-region networking infrastructure that can support high performance communication into, out of, and across public cloud geographic regions. In this paper, we lay the foundation for a comprehensive study and real time monitoring of various characteristic of networking within and between public clouds. We start by presenting CloudCast, a world-wide and expandable measurements and analysis system, currently (January 2019)collecting data from three major public clouds (AWS, GCPand Azure), 59 regions, 1184 intra-cloud and 2238 cross-cloud links (each link represents a direct connection between a pair of regions), amounting to a total of 3422 continuously monitored links and providing active measurements every minute.CloudCast is composed of measurement agents automatically installed in each public cloud region, centralized control, measurement data base, analysis engine and visualization tools. Then we turn to analyze the latency measurement data collected over almost a year . Our analysis yields surprising results. First, each public cloud exhibits a unique set of link latency behaviors along time. Second, using a novel, fair evaluation methodology, termed similar links, we compare the three clouds. Third, we prove that more than 50% of all links do not provide the optimal RTT through the methodology of triangles. Triangles also provide a framework to get around bottlenecks, benefiting not only the majority (53%-70%) of the cross-cloud links by 30% to 70%, but also a significant portion (29%-45%) of intra-cloud links by 14%-33%.

翻译：公共云层是过去十年中最繁荣的技术之一。 公共云层的主要应用需要全球范围分布和分布式服务器之间的大量数据交换。 为此,主要云源提供商投入了数百亿美元,用于建设全球范围跨区域网络基础设施,这些基础设施可以支持高性能通信进入、进出和跨越公共云层地理区域。在本文中,我们为全面研究和实时监测公共云层内部和之间联网的各种特征奠定了基础。我们首先展示了云层CloudCast,这是一个全球范围的、可扩展的测量和分析系统,目前(2019年1月从三大主要公共云层(AWS、GCPand Azure)收集数据,59个区域,1184个云层内部和2238个跨云层链接(每个链接代表一对区域之间的直接连接),总计有3422个持续监测的链接,每分钟提供积极的测量。CloudCast由每个公共云层区域自动安装的测量剂、集中控制、测量数据基、分析引擎和视觉化工具组成。 然后我们转而不用分析工具来分析云层测量三个云层测量度测量数据, 一个在近50年收集的云层链接的云层测量数据, 。 我们通过一个重要分析方法,每个分析结果,每个分析结果,每个分析一个比一个新的分析结果, 以30。