# A Reliable Routing Algorithm Based on Path Satisfaction in the Energy Internet
## 4 Solution Approach
### Path Satisfaction-Based Service-Aware Routing Algorithm (PSSRA) for the Energy Internet
Assume that each fiber contains 32 FSs, and the bandwidth of each frequency slot is 12.5 GHz. The guard band occupies 1 FS, and each TS lasts 10 ms. There are in total 15 TSs within a given period. (b) The 14-node Network

The 14-node NSFnet contains 21 links, and the average node degree is 3. The SRLG configuration is shown in Figure 2. Let node 11 be the dispatching center. We assume that there are three voltages. Here, 6 and 13 are 500 kV substations, 1, 5, 8, and 10 are 330 kV substations, and the remaining nodes are 220 kV substations. If the voltage scale of the substation exceeds 220 kV, then they are connected by OPGW cables. Suppose the bandwidth of each fiber is 4.475 THz, which is divided into 358 FSs based on the standard FS bandwidth. The number of TSs is 40. The other parameters are identical to those in the 7-node network. (c) The 28-node Network

The 28-node Network derives from the power optical transmission network of a city in China [42] as shown in Figure 6. There are 28 substations and 47 links in total. The nodes are divided into four types according to the scale of voltage. Nodes 5, 20, and 29 are 500 kV substations represented in dark blue; 1, 7, 12, 17 are 110 kV substations represented in green. The rest of the nodes are 220 kV substations represented in blue. The control center is located at node 14, represented in red. Similarly, links with 500 kV, 220 kV, and 110 kV are denoted in red, black, and green, respectively. The number on the link stands for transmission distance, and the average node degree in the network is 3.2. Figure 5: 14-node NSFnet. ### Evaluation Metrics

Two evaluation metrics, the service blocking ratio (SBR) and Jain\({}^{\prime}\)s fairness index (JFI) were leveraged to evaluate the algorithm performance. * The SBR is the ratio of the blocked services to the total number of services within a time period. The algorithm with a low SBR attains high performance. It is formulated as follows: \[SBR=1-\frac{\sum_{r\in\mathbb{S}}S_{r}}{\mathcal{R}},\;\mathbb{S}\subseteq \mathbb{R}\] (26) where \(\mathbb{S}\) is the satisfied service set. * The JFI is used to measure the service distribution with different routing strategies. It is in the range of \(1/|E|\) to 1, and the larger JFI indicates a more even service distribution in the network. It is computed as follows: \[JFI=\frac{(\sum_{e\in E}\tau_{e})^{2}}{\left|E\right|\left(\sum_{e\in E}\tau_{ e}^{2}\right)}\] (27) where \(\tau_{e}\) indicates the occupied number of link e in a time period. ### Performance Evaluation

The SBR of different service levels with the PSSRA algorithm in the 7-node network is shown in Figure 7. The change of SBR reflects the effectiveness of the routing algorithm, and a lower SBR indicates a better transmission performance and high routing reliability. It is noted that the SBR of level 1 services always remains zero, which means that all services are successfully delivered. This is because the highest level of these services is preferentially processed. We also find that the SBRs of the other three levels increase with the increasing number of services. Furthermore, the SBRs of services with levels 3 and 4 are higher than the services of level 2, and the average SBRs are 4.9% and 5.6%, respectively. This occurs because of the routing path selection and abundant bandwidth resources on the links. SP-based approaches merely focus on latency requirements, which is likely to result in service aggregation and high SBRs. Figure 6: 28-node network. The change of balancing service requests with different approaches in the 7-node network is shown in Figure 8. It is obvious that JFI values gradually decrease with services increasing. When there are a fewer number of services, more feasible paths could be found. Thus, services are distributed across different routing paths, and consequently the network risk is evenly balanced.