# A Game Model and Fault Recovery Algorithm for SDN Multi-Domain
## 4 SDN-MARA Algorithm
### Design of the SDN-MARA Algorithm
#### 4.3.3 Game-Enhanced Dynamic Mapping Algorithm for Switches and Target Controllers
Specifically, it can reduce the delay by up to 11% and averages a reduction of 6.5%. This improvement is attributed to the continuous optimization of target controller selection facilitated by the multi-population particle swarm algorithm with repulsive interaction. Particularly, the interaction mechanism of multiple populations in phases two and three enhances the algorithm's ability to identify global optimal efficiently, thereby saving optimization time. Additionally, the SDN-MARA algorithm takes into account both the migration costs of out-of-control switches and the load pressures on target controllers, resulting in shorter fault recovery delays compared to the other three algorithms. #### 5.2.3 Comparison of Target Controller Load Pressure

Figure 6 presents a comparative experiment on the remaining capacity ratio of target controllers after taking over the out-of-control switches. As shown in the figure, the remaining capacity ratio of target controllers under the SDN-MARA algorithm remains relatively consistent. This is primarily because the algorithm considers the remaining capacity of all controllers participating in the decision-making process when selecting target controllers for out-of-control switches. Controllers with larger remaining capacity will take over more out-of-control switches, ultimately achieving a balanced distribution of the load among target controllers. Figure 5: Comparison of fault recovery delays. The BCS algorithm fails to update the remaining capacity of target controllers in time, resulting in an overall load performance that is lower than that of the SDN-MARA algorithm. The SBC algorithm does not account for the load of target controllers, leading to a highly uneven distribution of load among them. The performance of the CFRS algorithm is generally consistent with that of the SDN-MARA algorithm, as CFRS achieves a uniform distribution of out-of-control switches by setting load ranges for target controllers and continuously updating their load. ## 6 Conclusions

This paper addresses the reliability issues of controllers in an SDN multi-domain controller environment by proposing an SDN-MARA algorithm. Comparative experimental results demonstrate that the proposed model and algorithm show advantages in terms of the migration cost of out-of-control switches, fault recovery delay, and remaining capacity of target controllers. Future research will focus on the consistency of data across control nodes when multiple controller fails, controller migration, and domain restructuring, as well as extending the autonomous failure recovery algorithm for controllers to distributed computing. Conceptualization, T.X. and C.C. ; methodology, C.C. and Y.Z. ; software, C.C. and T.X. ; validation, K.H. and Y.Z. ; writing--original draft, T.X. and C.C. ; writing--review and editing, K.H. and Y.Z. ; funding acquisition, Y.Z. All authors have read and agreed to the published version of the manuscript. This work is supported by the National Natural Science Foundation of China under Grant (No.62072235). Not applicable. Data Availability Statement: Data are contained within the article. The authors declare no conflicts of interest. ## References

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