The Art of Detecting Forwarding Detours
The Art of Detecting Forwarding Detours
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检测转发绕道的艺术
DOI：
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发表时间：
2021
影响因子：
5.3
通讯作者：
A. Pescapé
中科院分区：
文献类型：
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作者：
Julian M. Del Fiore;V. Persico;Pascal Mérindol;C. Pelsser;A. Pescapé
截至2021年3月，完整的互联网订阅源达到约867K前缀，在过去10年中一直以每年50K前缀的≈速度增长。为了平衡这种持续增长，自治系统(AS)可以过滤前缀、执行前缀聚合和使用默认路由。尽管有效，但这种变通办法可能会导致路由不一致，即沿转发路由的路由器将相同的IP地址映射到不同的IP前缀。反过来，作为与这些不同前缀相关联的边界路由器的出口可能会不同。对于某些前缀，可能会出现转发迂回(FD)，即流量可能偏离最佳IGP路径。在这项工作中，我们研究了FDs现象，并推导了一种检测它们的方法。特别是，我们的工具能够精确定位多个前缀受FDs影响的情况。我们从NLNOG环监控基础设施的100个有利位置进行了测量，在54个AS中有25个发现了FD。我们看到FD是异质的，即前缀和AS的数量，我们检测FD的边界路由器之间强烈依赖于所研究的AS。最后，我们发现了一个显著的二元效应，使得在AS的两个边界路由器之间穿越的所有中转流量要么绕道，要么都不绕道。
The full Internet feed, reaching ~867K prefixes as of March 2021, has been growing at ≈50K prefixes/year over the last 10 years. To counterbalance this sustained increase, Autonomous Systems (ASes) may filter prefixes, perform prefix aggregation and use default routes. Despite being effective, such workarounds may result in routing inconsistencies, i.e., in routers along a forwarding route mapping the same IP addresses to different IP prefixes. In turn, the exit AS border routers associated with these distinct prefixes may potentially differ. For some prefixes, forwarding detours (FDs) may occur, i.e., traffic may deviate from best IGP paths. In this work we investigate the phenomenon of FDs and derive a methodology to detect them. In particular, our tool is able to pinpoint cases where multiple prefixes are subject to FDs. We run measurements from 100 vantage points of the NLNOG RING monitoring infrastructure and find FDs in 25 out of 54 ASes. We see that FDs are heterogeneous, i.e., the number of prefixes and AS border routers in between which we detect FDs strongly depend on the studied AS. Finally, we discover a remarkable binary effect such that either all transit traffic traversing between two border routers of an AS detours, or none does.