# BPDM-GCN: Backup Path Design Method Based on Graph Convolutional Neural Network
## 2 Related Research
### Fast Recovery Method of Link Failure Based on Data Plane  
The problem of extended fault link recovery time in control plane-based fault link recovery method is addressed. The fault link recovery method based on the data plane involves pre-calculating primary and backup paths via the SDN controller. In the event of a link failure, the switch directs phasor data packets to follow the backup path without requiring interaction with the controller. This approach effectively minimizes delays in fault link recovery. [PERSON] et al. took reducing the number of interrupted traffic caused by link failures as the optimization goal, and formalized the selection of backup paths as an integer programming problem to reduce the demand for backup flow rules and backup bandwidth [15]. [PERSON] et al. employed the fault-tolerant fast-switching technology and fault recovery mechanism of the SDN controller to establish multiple backup paths between the source and destination points, effectively addressing both single-path and multi-path failure issues [16]. In the approach proposed by [PERSON] et al., backup paths are stored in advance in the switch. In the event of a link failure, the interrupted data packets are aggregated into a flow entry using VLAN ID, thereby reducing the number of traffic packets [17]. [PERSON] et al. employed Markov chains to assess the significance of links, implemented backup pathways for primary pathways in switches in advance, and stored backup pathways for secondary links in controllers, thereby effectively reducing the consumption of backup resources [18]. The data plane fault link recovery method, which is based on the control plane fault recovery method, addresses the issue of prolonged recovery times. However, the pre-calculated backup path in the switch does not fully consider the link load condition. In the event of a link failure, there is a risk of secondarylink failure due to congestion on the backup path, which can impede the stable transmission of phasor data in the communication network of the wide-area measurement system.  
In order to address the aforementioned issues, this paper proposes the integration of SDN into the wide-area measurement communication network. Furthermore, it puts forth BPDM-GCN with the objective of enhancing the recovery success rate of faulty links in the communication network topology of wide-area measurement systems of varying sizes. The BPDM-GCN method employs an iterative training process based on the transmission delay, bandwidth occupancy, and packet loss rate of the phasor data link within the communication network of the wide-area measurement system. This process involves multiple interactions between the intelligent agent and the communication network, with the objective of identifying the optimal link weight for calculating the backup path. Based on the optimal link weight in the network topology, with link load balancing and shortest path as the optimization goals. A backup path based on the incremental shortest path tree has been designed and implemented to achieve rapid recovery of faulty links in the communication network of the wide-area measurement system.