Anycast has been widely adopted by today's Internet services, including DNS, CDN, and DDoS protection, in which the same IP address is announced from distributed locations and clients are directed to the topologically-nearest service replica. Prior research has focused on various aspects of anycast, either its usage in particular services such as DNS or characterizing its adoption by Internet-wide active probing methods. In this paper, we first explore an alternative approach to characterize anycast based on previously collected global BGP routing information. Leveraging state-of-the-art active measurement results as near-ground-truth, our passive method without requiring any Internet-wide probes can achieve 90% accuracy in detecting anycast prefixes. More importantly, our approach uncovers anycast prefixes that have been missed by prior datasets based on active measurements. While investigating the root causes of inaccuracy, we reveal that anycast routing has been entangled with the increased adoption of remote peering, a type of layer-2 interconnection where an IP network may peer at an IXP remotely without being physically present at the IXP. The invisibility of remote peering from layer-3 breaks the assumption of the shortest AS paths on BGP and causes an unintended impact on anycast performance. We identify such cases from BGP routing information and observe that at least 19.2% of anycast prefixes have been potentially impacted by remote peering.

中文翻译：

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全球路由中任播的被动分析

Anycast 已被当今的 Internet 服务广泛采用，包括 DNS、CDN 和 DDoS 保护，其中从分布式位置宣布相同的 IP 地址，并将客户端定向到拓扑最近的服务副本。先前的研究集中在任播的各个方面，无论是在特定服务（如 DNS）中的使用，还是通过互联网范围内的主动探测方法来表征其采用。在本文中，我们首先探索了一种基于先前收集的全局 BGP 路由信息来表征任播的替代方法。利用最先进的主动测量结果作为近乎真实的结果，我们的被动方法无需任何 Internet 范围内的探头即可在检测任播前缀方面达到 90% 的准确度。更重要的是，我们的方法基于主动测量发现了先前数据集遗漏的任播前缀。在调查不准确的根本原因时，我们发现任播路由与越来越多地采用远程对等互连有关，这是一种第 2 层互连，IP 网络可以远程与 IXP 对等而不实际出现在 IXP 上。来自第 3 层的远程对等的不可见性打破了 BGP 上最短 AS 路径的假设，并对任播性能造成了意想不到的影响。我们从 BGP 路由信息中识别出此类情况，并观察到至少 19.2% 的任播前缀可能受到远程对等互连的影响。我们发现，任播路由与远程对等互连的采用率越来越高，这是一种第 2 层互连，IP 网络可以远程与 IXP 对等，而无需实际出现在 IXP 上。来自第 3 层的远程对等的不可见性打破了 BGP 上最短 AS 路径的假设，并对任播性能造成了意想不到的影响。我们从 BGP 路由信息中识别出此类情况，并观察到至少 19.2% 的任播前缀可能受到远程对等互连的影响。我们发现，任播路由与远程对等互连的采用率越来越高，这是一种第 2 层互连，IP 网络可以远程与 IXP 对等，而无需实际出现在 IXP 上。来自第 3 层的远程对等的不可见性打破了 BGP 上最短 AS 路径的假设，并对任播性能造成了意想不到的影响。我们从 BGP 路由信息中识别出此类情况，并观察到至少 19.2% 的任播前缀可能受到远程对等互连的影响。