中文摘要：

目前对Internet拓扑结构的扁平化趋势的研究多集中在定性描述上,没有大规模的测量数据支撑。从域间路由的角度,分析了Internet层级结构和互连策略的演变趋势。发现Internet扁平化的主要原因是绕过Tier-1ISP以及peer-to-peer链路比例的增加。测量了路由基础设施的变化情况,发现IXP在数量和地理位置上都快速增长,极大地方便了内容提供商和内容分发网络的扩张。测量结果能够加深对Internet生态系统的理解,有助于未来互联网架构的设计。最后分析了Internet扁平化的原因和影响。

英文摘要：

There was few large-scale quantitative measurement study of flattening trends of the Internet topology from the perspective of inter-domain routing. This paper analyzed the evolutionary trends of the Internet hierarchy and the interconnection policies,using fifteen years of historical datasets from RouteViews and RIPE. It found that the Internet was becoming flatter mainly due to bypassing the Tier-1 ISPs on AS-paths and the notable increase of peer-to-peer links. It also examined the global routing infrastructure,and found that IXPs were increasing rapidly in number and expanded to broad areas around the world,which greatly facilitated the expansion of major content providers and content delivery networks to most regions in the world.The measurement results strongly confirm the flattening trends of Internet,and will help understanding of the Internet AS-level ecosystem and the design of future Internet architecture.