Accurate link latency information is essential for various traffic engineering problems, such as routing design and network diagnosis. However, due to the routing constraints, link latency measurement is still a challenging problem in hybrid software-defined networks (SDNs) and little literature has been found in this field. Due to cost, a hybrid SDN composed of conventional routers and SDN switches will exist for some time to come, which shows the necessity and the urgency to address this problem. In this paper, we investigate this link latency measurement problem in two different scenarios: 1) the conventional routers can only support the shortest path routing protocol, and 2) the conventional routers can support source routing protocol. For both of these scenarios, we show how to deploy a minimum number of monitors and how to construct measurement paths between monitors to measure all the link latencies. Several algorithms are presented to solve these problems and the evaluations on different topologies prove the superiority of the proposed methods.

中文翻译：

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混合 SDN 中链路延迟测量的监视器放置


准确的链路延迟信息对于路由设计和网络诊断等各种流量工程问题至关重要。然而，由于路由限制，链路延迟测量仍然是混合软件定义网络（SDN）中的一个具有挑战性的问题，并且该领域的文献很少。由于成本的原因，传统路由器和SDN交换机组成的混合SDN将在未来一段时间内存在，可见解决这一问题的必要性和紧迫性。在本文中，我们研究了两种不同场景下的链路延迟测量问题：1）传统路由器只能支持最短路径路由协议，2）传统路由器可以支持源路由协议。对于这两种场景，我们展示了如何部署最少数量的监视器以及如何在监视器之间构建测量路径以测量所有链路延迟。提出了几种算法来解决这些问题，并且对不同拓扑的评估证明了所提出方法的优越性。