# A Dynamic Restructuring Algorithm Based on Flexible PON Slices
## 5 Discussion  
The reason why the DRA algorithm can achieve a high performance is that DGA only divides the graph into two subgraphs in each iteration, and deletes a subgraph after calculation and exchange is completed. The initial graph of each dichotomy is the remaining node after deleting the subgraph in the previous step, which ignores the effect of the results of previous partitions on subsequent partitions. (For example, assuming that the node switch gain of two nodes \(i\) and \(j\) is 0, the initial graph with \(i\) or \(j\) in the next iteration will yield different results). Therefore, the result of each iteration is a locally optimal solution rather than a globally optimal solution. Reviewing the DRA, it divides the whole graph into M subgraphs at the beginning, and then calculates for all nodes. At the same time, the changes of traffic by exchanging two nodes of two subgraphs are reflected on at the global level, and will be taken into account in the next calculation of exchange gain. During the whole process, there is no need to delete the subgraph and all nodes are considered in each calculation. In this way, not only is the problem of ignoring the influence of previous steps in multiple partitions solved, but also the global optimal solution is obtained. Therefore, DRA algorithm can achieve a higher performance than DGA. Compared with DONUSA, the result of DRA is the optimal solution at the global level, which is not affected by randomness of initialization. Therefore, DRA has better performance and is more stable than the DONUSA algorithm.  
As can be seen from Figure 4, the DRA algorithm still achieves higher performance as the number of ONUs increases. In addition, it can also be seen from Figure 5 that with the increase in the number of ONUs, the improved performance of DRA algorithm compared to the existing algorithm is maintained between 10% and 30%. These results indicate that the proposed DRA algorithm has good expansibility and stability. With the deepening and  
Figure 6: The traffic gain of 3 algorithms with 512 ONUs.  
popolarization of 5G technology in the future, the expansion of the network will require more network terminals. In this case, the proposed DRA algorithm with strong scalability and stability will have better application value.  
In addition, the DRA algorithm is implemented on the SDN controller, and the calculated results need to be transmitted to the basic network infrastructure through the southbound interface and make some corresponding adjustments. So the whole communication process is based on software-defined network technology, which is the core technology of 5G. Therefore, the proposed DRA algorithm is applicable to all multi-OLT-based access networks that support software-defined technology, and has a very broad application prospects and scope.  
Considering that there may be some differences between the simulation conditions and the actual scene, we will deploy the algorithm on the actual optical access network experiment platform for real scene verification in the subsequent research, so as to ensure the effectiveness of the algorithm in practice. We will also add more different scenarios and factors during the verification process. In addition, the algorithm is deployed in the SDN controller at the local end, which may cause the communication compatibility issues between the SDN controller and the existing network infrastructure. For example, in the actual application process of the algorithm, the existing network infrastructure needs to be upgraded to support the Openflow protocol. At the same time, the existing Openflow protocol should be extended to include instructions that can control the dynamic slicing process of the existing network infrastructure. Therefore, how to extend the Openflow protocol based on the results of this algorithm is also one of the future research directions. Furthermore, we will also consider adding the corresponding authorization mechanism in the SDN controller.