# A Reliable Routing Algorithm Based on Path Satisfaction in the Energy Internet
## 1 Introduction  
Energy Internet (EI) is the trend of smart grid evolution from the perspective of energy resource allocation. As a typical cyber-physical system (CPS), it consists of the following two parts: the energy system and the information communication system (ICS) [1, 2, 3]. Generally speaking, the communication network is a high-speed, two-way, integrated private network, which is usually responsible for ensuring service transmission and providing necessary auxiliary supports for the physical network. In this paper, we focus on the reliable service transmission of EI in China, which is different from the microgrids in other countries. According to service attributes and their roles in the network, services are often divided into control services and management services. Control services are sensitive to latency and critical to guarantee the smooth operation of EI. Therefore, they are often deliveredon dedicated lines and require configured dual-route paths. Management services mainly include supervisory control, data acquisition (SCADA), and energy management systems (EMSs). They are delivered on the data communication network via Multi-Protocol Label Switching Virtual Private Networks (MPLS VPNs) or tunnels due to the need for isolation and security. Additionally, new technologies, such as the network intellectualization and virtualization of the secondary systems, that is the ICS, cloud computing, and big data have developed rapidly. Therefore, IP-based services have experienced significant transformations. Typically, the service bandwidth gradually increases from 64 kbit/s or 2 Mbit/s to 1 GE/10 GE. Meanwhile, the volume of services increases dramatically, which results in a heavier network burden. Moreover, most services are sensitive to QoS guarantees, fine control, and network management. Particularly, control services in the EI have the characteristic of aggregation. In other words, they are commonly transmitted from lower voltage substations to higher-level or control centers, which is different from the public network. Therefore, this may lead to some critical substations or optical fibers carrying more services than others. Consequently, the imbalanced service distribution across the network poses a significant threat to the stability of the ICS and affects the smooth operation of the EI. Moreover, with the rise of new services, the discrepancy communication requirements have gradually expanded. The traditional power communication management and control system toughly guarantees reliable transmission performance due to a lack of coordinated network planning, network compatibility, and poor ability to obtain the state of the whole network, which seriously restricts the intelligent development of the network. Hence, how to ensure the services have an even distribution, reliable transmission, and enhanced network resource utilization is still a great challenge. It is well known that internet protocol (IP)/Optical networks are independently planned, managed, and operated in the traditional distributed architecture. To achieve coordination management and control of the networks is a critical issue in the development of communication networks. The coordinated operation will greatly enhance the network's overall operation efficiency and reduce construction and maintenance costs. At the same time, along with the development of ROADM (Reconfigurable Optical Add-Drop Multiplexer) and OTN (Optical Transport Network), the optical network gradually enables an ability to deal with resource scheduling and flexible network configuration dynamically. Additionally, due to the global view of the network, the separation of the control plane and the forwarding plane, and the programmable control, Software Defined Networking (SDN), provides a new solution to achieve a coordinated operation of cross-layer networks. Moreover, the logically centralized SDN has the potential to realize agile service provisioning, networking interaction and link protection, efficient resource coordination, etc.