## 5 Topology and Overload Detection
### Overload Detection Results  
We propose the use of two protocols--CPSP (Centralized Periodic Status Ping) and TDLP (Token-based Distributed Load Polling)--both operating on the Token Bus protocol to enhance overload detection and system observability [23; 24]. These protocols assist the operator in easily identifying the location of an overload when it occurs. CPSP functions as a real-time query mechanism for monitoring the total CPU utilization of each sub-station, as shown in Figure 8. Since sub-stations operate at different frequencies depending on their task loads, CPSP sends a variable number of query requests to each station accordingly. For example, if Station A executes five operations and Station B performs three within a given time window, CPSP queries Station A five times and Station B three times, enabling fine-grained utilization tracking. Figure 7 presents the experimental results of CPSP in action. Under nominal conditions, the main station periodically transmits ping signals to sub-stations. In this scenario, Station A (IP: 202.30.106.1) received five status requests, while Station E (IP: 202.30.106.241) received only one, reflecting their respective operational loads. Figure 8 shows the output log from a terminal-based network monitoring tool, used here to validate the behavior of the CPSP (Centralized Periodic Status Ping) protocol in a DCS environment. The left pane displays raw ICMP (Internet Control Message Protocol) echo request results--commonly known as \"ping\" results--for two different sub-stations. The first block of results corresponds to Station A with IP address 202.30.106.1, where five ping requests were transmitted and successfully received, indicating 0% packet loss and consistent response times (minimum: 1.435 milliseconds; average: 3.347 milliseconds; maximum: 10.793 milliseconds). The second block shows results for Station B with IP address 202.30.106.250, where four pings were transmitted with similarly stable round-trip times, also achieving 0% packet loss. On the right side of the interface, the file _test_config.txt_ is shown, which appears to define the operational parameters of each sub-station under the CPSP protocol. This configuration file maps each IP address to a specific polling count (e.g., Station A receives five queries, Station E only one), aligning with the variable-frequency querying mechanism described in the protocol design. These results confirm the CPSP system's capability to selectively and periodically monitor CPU utilization across distributed nodes with minimal  
Figure 8: Screenshot of CPSP simulation results. communication overhead and high reliability, making it suitable for real-time performance diagnostics in DCS networks. In parallel with CPSP, the Token-based Distributed Load Polling (TDLP) protocol was utilized to capture live data packets from each sub-station during query execution. The collected packet data were analyzed and converted into real-time memory utilization metrics, offering additional insight into system resource consumption. To support this functionality, a specialized network monitoring tool--Sub-Station Traffic Management (SSTM)--was employed to monitor packet flows across the DCS bus topology. SSTM enables the capture of TCP/IP packets traversing the network and provides real-time visual feedback of communication between client and server nodes. As illustrated in Figure 8, SSTM visualizes the packets entering each sub-station, thereby facilitating continuous observation of network load and memory usage in real time. This monitoring mechanism is critical for detecting potential overload conditions and ensuring reliable system performance. Figure 9 displays a packet-level capture performed using Wireshark, a widely adopted network protocol analyzer [25], to monitor communication traffic within the proposed DCS network environment.