In a distributed Software Defined Networking (SDN) architecture, the Quality of Service (QoS) experienced by a traffic flow through an SDN switch is primarily dependant on the SDN controller to which that switch is mapped. We propose a new controller-quality metric known as the Quality of Controller (QoC) which is defined based on the controller’s reliability and response time. We model the controller reliability based on Bayesian inference while its response time is modelled as a linear approximation of the M/M/1 queue. We develop a QoC-aware approach for solving (i) the switch-controller mapping problem and, (ii) control traffic distribution among the mapped controllers. Each switch is mapped to multiple controllers to enable resilience with the switch-controller mapping and control traffic distribution based on the QoC metric which is the combined cost of controller reliability and response time. We first develop an optimization programming formulation that maximizes the minimum QoC among the set of controllers to solve the above problem. Since the optimization problem is computationally prohibitive for large networks, we develop a heuristic algorithm — Qoc-Aware switch-coNTroller Mapping (QuANTuM) — that solves the problem of switch-controller mapping and control traffic distribution in two stages such that the minimum of the controller QoC is maximized. Through simulations, we show that the heuristic results are within 18% of the optimum while achieving a fair control traffic distribution with a QoC min-max ratio of up to 95%.

中文翻译：

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软件定义网络中的 QoC 感知控制流量工程

在分布式软件定义网络 (SDN) 架构中，通过 SDN 交换机的流量所经历的服务质量 (QoS) 主要取决于该交换机映射到的 SDN 控制器。我们提出了一种新的控制器质量指标，称为控制器质量 (QoC)，它是根据控制器的可靠性和响应时间定义的。我们基于贝叶斯推理对控制器可靠性进行建模，同时将其响应时间建模为 M/M/1 队列的线性近似。我们开发了一种 QoC 感知方法来解决 (i) 交换机控制器映射问题和 (ii) 控制映射控制器之间的流量分配。每个交换机都映射到多个控制器，以根据 QoC 指标（控制器可靠性和响应时间的综合成本）通过交换机-控制器映射和控制流量分配实现弹性。我们首先开发了一个优化编程公式，该公式可以最大化控制器集合中的最小 QoC 来解决上述问题。由于优化问题对于大型网络在计算上是令人望而却步的，因此我们开发了一种启发式算法——Qoc-Aware switch-conNTroller Mapping (QuANTuM)——它分两个阶段解决了交换机-控制器映射和控制流量分配的问题，使得控制器 QoC 最大化。通过模拟，