# A Congestion Control Strategy for Power Scale-Free Communication Network
## 3 Congestion Control Strategy for the Power Scale-Free Network
### Integrated Routing Strategy  
In the power communication network, the shortest path routing strategy is widely used, which reflects an incomparable superiority when network packets are less. However, as network packets increase, the packets prefer to go through these hub nodes under the shortest path routing strategy, which further exacerbates network congestion and even endangers the normal operation of the power grid. The real-time queue lengths of nodes are considered as routing costs to dramatically redistribute the overall data flow on all nodes under the global dynamic routing strategy. However, the routing table needs to be updated under the global dynamic routing at each time step, and much of the computational resource will be consumed. Integrated routing combines the advantages of these two routing strategies and makes up for the weakness. If the shortest routing is adopted to transmit I-level \begin{table}
\begin{tabular}{c c} \hline \hline
**Service Type** & **Examples** \\ \hline voice service & dispatching telephone, conference telephone, etc. \\ data service & line relay protection data, dispatching automation data, etc. \\ video service & remote video conference, surveillance video, etc. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Service type of power communication services. \begin{table}
\begin{tabular}{c c} \hline \hline
**I-Level** & **II-Level** \\ \hline relay protection data & video conference \\ safety and stability control data & lightning location monitoring \\ dispatching telephone & office automation \\ protection information management & electric metering telemetry \\ dispatching automation & video monitoring of substations \\ wide area measurement & administrative telephone \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Classification of power communication services. packets and the global dynamic routing is adopted to transmit II-level packets, which can guarantee the real-time requirement of the important communication services and reduce the network congestion, the incoming packets to different paths from the source to the destination are evenly distributed under the integrated routing, and the fundamental structure of the node queue is shown in Figure 3.  
When the packet enters the router, it must pass through the following four processes: (1) the packet is stored in the buffer of the receive port; (2) the packet is processed by the distribution scheduler and copied to the buffer queue of the forwarding port; (3) each queue packet is copied to the output buffer queue by the packet polling scheduler according to the fair queuing algorithm; (4) the packet is forwarded, and the processes are shown in Figure 4.  
The scale-free characteristic of the power communication network causes the network congestion, which occurs at the hub nodes first. As shown in Figure 4, Node 10 is the hub node in the network. It can be seen from Figure 5 that Hub Node 10 usually can be passed through to obtain the shortest path in data transmission, which results in the load of Hub Node 10 and the link it is connected to being heavy. For example, if I-level packets select the delivery path \(4\to 10\to 7\) and II-level packets select the delivery path \(4\to 5\to 2\to 1\to 7\), this can reduce the load of Hub Node 10 and guarantee the reliable delivery of I-level packets. In the integrated routing, each node stores and maintains two kinds of routing tables, which include the routing table of I-level services and the routing table of II-level services. The power communication network adopts the TCP/IP (Transmission Control Protocol/Internet Protocol), which has a large range of traffic data and a high real-time requirement, and the end to end TCP protocol allows senders to reduce traffic. Each node is considered as both host and router to generate packets or forward packets. The rules of the integrated routing strategy based on the classification of power communication services are as follows. 1. The topological graph is constructed based on the modeling rules;
2. Wait for the business request.