## 5 Numerical Results and Performance Analysis
### Simulation Setup  
In evaluation scenarios, the simulation setup includes two main parts: a substrate physical network (i.e., actual communications networks) and logical networks (i.e., communication service instances of NSIs). The sample substrate network topology consists of access layer network, aggregation layer network and core layer network. The number of substrate network nodes is fixed and the substrate link is randomly drawn with specific substrate node connectivity. Each link in the substrate network graph is weighted by link length and bandwidth. As shown in Table 2, the substrate network capacities of the access, aggregation, and core layer networks are set to 40 Gbps, 80 Gbps, and 80 Gbps, respectively, according to the future planning of 5G high-capacity and highly scalable transport network [48; 49]. Similarly, the setup of substrate links' length follows the practical structure of the backhaul network, as given in [50]. The node connectivity can describe the number of physical links, for example, when it is set to 0.4, the current node will randomly connect to 40% of the remaining nodes. Common to all proposals, the average substrate node connectivity is always set to 0.4 or 0.5 for ring protection [39]. In order to test the proposed method in improving the network serviceability, we reduce the connectivity of some nodes, randomly taking values between 0.3 and 0.4. The nodes between different layer networks are randomly connected with the same connectivity. We assume that the substrate link is laid by the optical fiber so that the weight factor \(\theta\) of the path transmission is fixed as well. An example of the communications network topology in a timestamp of the simulation is shown in Figure 3, which is a scaled-down version of the practical backhaul transport network. At each timestamp, we generate the substrate network topology randomly according to the node number and node connectivity, as well as the upper bound of network capacity and link length. The comparison value is the average of the results in multiple simulation timestamps to reduce the error. The physical nodes in infrastructure networks are divided into three sets corresponding to the three-layer networks. The access layer network deploys the largest number of nodes with small node spacing and link bandwidth capacity, which is opposite to the characteristics of nodes in the core layer network. For the parameters of NS, we consider the resource allocation over NSIs tailored for three types of services, i.e., the small-volume critical communications (s-VCC) slice, extreme real-time communications (eRTC) slice and enhanced mobile broadband access (eMBB) slice in dense areas. For each slice type, we also initialize three NSIs respectively, where NS 1, 2 and 3 represent the NSIs of s-VCC, NS \(A\), \(B\) and \(C\) represent the ones of eRTC and NS \(a\), \(b\) and \(c\) represents the ones of eMBB. As slice performance requirements explicitly differentiate, the corresponding slice traffic volume and latency threshold are reasonably set according to the slice type [29; 41], as shown in Table 2. The topology of traffic flow in an NSI is randomly generated with 8 VNFs weighted by the forwarded traffic demands. According to the assumption, each VNF is only used once at most in the topology of a communication service instance. Table 2 summarizes the simulation parameters.