基于Openflow的智能电网网络链路故障恢复研究

Research on Fast Recovery from Link Failures Based on Openflow in Smart Grid

摘要: 本文设计了一种智能电网中的链路故障快速恢复算法，并对算法进行了验证。本文方法解决了链路故障恢复三个方面的问题：1) 链路故障探测，2) 计算备份多播树的算法，3) 快速备份树的建立。首先，本文设计了基于Openflow的链路故障探测和上报机制，来探测链路故障。Openflow是一种开源框架，将网络管理的控制和转发平面进行分离。其次，本文设计了多播回收机制，通过计算备份多播树来最小化控制信号的开销。本文证明了多播回收问题是一个NP难问题，并提出一种相应的算法来解决该问题。最后，本文设计了一种优化算法，通过在多播组之间共享规则来查找到接近最优的转发集合，同时降低了备份树和控制机制之间的时间开销。本文在POX Openflow控制器上使用Mininet仿真器评估了所提出的算法，量化了控制平面的信号和安装时间。

Abstract: In this paper, we design and evaluate algorithms for fast recovery from link failures in a smart grid communication network, addressing all three aspects of link failure recovery: 1) link failure detection, 2) algorithms for computing backup multicast trees, and 3) fast backup tree installation. Firstly, we design link-failure detection and reporting mechanisms that use Openflow to detect link failures when and where they occur inside the network. Openflow is an open source framework that cleanly separates the control and data planes for use in network management and control. Secondly, we formulate a new problem, MULTICAST RECYCLING, which computes backup multicast trees that aim to minimize control plane signaling overhead. We prove that MULTICAST RECYCLING is at least NP-hard and presents a corresponding approximation algorithm. Lastly, two control plane algorithms are proposed that signal data plane switches to install pre-computed backup trees. An optimized version of each installation algorithm is designed that finds a near minimum set of forwarding rules by sharing rules across multicast groups, thereby reducing backup tree installation time and associated control state. We implement these algorithms in the POX Openflow controller and evaluate them using the Mininet emulator, quantifying control plane signaling and installation time.