During the transition from traditional networks to pure Software-Defined Networks (SDNs), hybrid SDNs are derived to provide flexible services. Furthermore, developing effective failure protection algorithms is significantly urgent to improve the robustness and resilience of networks. In this paper, we propose several algorithms, including Straightforward Protection Path Selection with the Source and Destination-based Tunneling mechanism (S-PPSSDT), its simplification PPSSDT and Protection Path Selection with Load-Balancing (PPSLB) algorithms. Considering that the Protection Path Length (PPL) will affect the transmission delay of rerouted packets, S-PPSSDT leverages the source and destination-based tunneling mechanism to select optimum protection paths with the shortest length. Based on classification idea and optimization search, PPSSDT prunes unnecessary path searches in S-PPSSDT. Combining the tunneling mechanism with the priority-based Maximum Link Utilization (MLU) minimization approach, PPSLB also focuses on load balancing during failure protection to achieve potential congestion avoidance simultaneously. Besides, these algorithms redirect the traffic through various tunnels for affected paths by the non-shortest path routing capability of SDN switches. Extensive simulation results indicate that our proposed algorithms can effectively reduce the PPL and MLU of hybrid SDNs during failure protection, and have excellent performance under various network parameters compared with the state-of-the-art algorithms.
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