Measuring TCP Round-Trip Time in the Data Plane
Measuring TCP Round-Trip Time in the Data Plane
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DOI：
10.1145/3405669.3405823
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发表时间：
2020-08
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影响因子：
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通讯作者：
Xiaoqi Chen;Hyojoon Kim;Javed M. Aman;Willie Chang;Mack Lee;J. Rexford
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作者：
Xiaoqi Chen;Hyojoon Kim;Javed M. Aman;Willie Chang;Mack Lee;J. Rexford
我们提出了一种数据平面算法，被动和连续监测TCP流量的往返时间，通过匹配数据包与其相关的数据包，并计算时间差。与传统的基于主动探测或仅测量SYN/ACK数据包的测量系统相比，我们的算法被动地产生许多长时间运行的连接的样本。这使网络运营商能够实时观察异常RTT增加，这表明网络中可能存在安全或性能问题。为了满足严格的存储器大小和访问限制的可编程交换机，我们的算法使用了一个多级哈希表数据结构，以保持记录在飞行中的数据包，记录没有收到他们的数据被懒惰过期和覆盖。我们实现我们的算法上赤脚Tofino可编程开关。使用来自10 Gbps园区网络链路的真实流量跟踪进行的评估表明，我们的解决方案可以准确捕获99%的可用RTT样本，仅使用4 MB的数据平面内存。
We present a data-plane algorithm that passively and continuously monitors the Round-Trip Time of TCP traffic, by matching data packets with their associated acknowledgments and calculating a time difference. Compared with traditional measurement systems based on active probing or measuring only SYN/ACK packets, our algorithm passively produces many samples for long-running connections. This enables network operators to observe abnormal RTT increases, which signal possible security or performance issues in the network, in real-time. To satisfy the stringent memory size and access constraints of programmable switches, our algorithm uses a multi-stage hash table data structure to maintain records for in-flight packets; the records not receiving their acknowledgments are lazily expired and overwritten. We implement our algorithm on a Barefoot Tofino programmable switch. Evaluation using a real-world traffic trace from a 10 Gbps campus network link demonstrates that our solution can accurately capture 99% of available RTT samples, using only 4 MB of data-plane memory.