Software Defined Networking (SDN) takes out the control plane of the network elements and distributes it to separate entities named as controllers. The main aim of the Controller Placement Problem (CPP) is to compute the optimum locations for controller deployment and assignment of switches to respective controllers. Every controller failure results in disconnection of switches from the controller leading to reassignment of switches to one or more of the active controllers. In this paper, we propose a controller placement strategy for multiple link failures, considering the network properties, to minimize the worst case latencies. We propose the solution using decision making under uncertainty (and non-competitive situations). Our objective is to find the optimum positions in the network for controller placement with reduced Maximum Worst Case Latency (MWCL) and maximum utilization of the controller. In addition, we have proposed the constraint-based solution for reassignment of switches to active controllers in the network. We have evaluated the proposed methodologies on various network topologies from Internet Topology Zoo. It is found that the decision making under uncertainty provides a better solution on CPP as compared to the existing mathematical methods for any SDN network topology.

中文翻译：

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软件定义网络中基于故障的控制器放置

软件定义网络 (SDN) 取出网络元素的控制平面并将其分配给名为控制器的独立实体。控制器放置问题 (CPP) 的主要目的是计算控制器部署和将交换机分配给各个控制器的最佳位置。每个控制器故障都会导致开关与控制器断开连接，从而导致将开关重新分配给一个或多个活动控制器。在本文中，我们提出了一种针对多链路故障的控制器放置策略，考虑到网络特性，以最小化最坏情况的延迟。我们提出了在不确定（和非竞争情况）下使用决策制定的解决方案。我们的目标是找到网络中控制器放置的最佳位置，同时降低最大最坏情况延迟 (MWCL) 并最大限度地利用控制器。此外，我们还提出了基于约束的解决方案，用于将交换机重新分配给网络中的活动控制器。我们已经在 Internet Topology Zoo 的各种网络拓扑上评估了所提出的方法。发现与现有的任何 SDN 网络拓扑的数学方法相比，不确定性下的决策为 CPP 提供了更好的解决方案。