## 5 Topology and Overload Detection
### Proposed Protocol  
The major communication protocols used in bus topology are Carrier Sense Multiple Access with Collision Detection (CSMA/CD) and the Token Bus protocol [13; 15]. CSMA/CD offers the advantage of low implementation cost, primarily due to its simple control mechanism and the lack of need for a centralized network management system within the DCS environment. However, CSMA/CD presents limitations in scenarios requiring sensitive or deterministic control, such as prioritizing data transmission among stations. Additionally, it does not guarantee real-time processing, which is critical in industrial control applications. The Token Bus protocol similarly benefits from low cost, but it suffers from a significant drawback, increased network load, as every transmission from a single node is broadcast to all nodes in the network. This can lead to congestion and reduced communication efficiency, particularly in large-scale distributed systems. In order to validate of system topology, we investigate Network Animator (NAM), a visualization tool commonly used with the Network Simulator (NS2) to animate and analyze packet flow in network simulations [16]. It is widely used for educational and research purposes to visually verify the behavior of various network protocols and topologies [17; 18]. Figure 6 presents a simulation environment captured from Network Animator (NAM), a visualization tool used in conjunction with NS2 for analyzing data transmission behavior in network protocols [19]. This simulation illustrates a bus topology configuration where nodes are organized into two rows. The upper row includes nodes labeled 0, 2, 4, and 6, while the lower row includes nodes 1, 3, 5, and 7. In particular, Node 9, positioned on the far left, is designated as the source or control node, responsible for initiating communication across the network. The horizontal line dividing the two rows symbolizes the shared communication medium or backbone bus, which is a defining feature of the bus topology. Figure 6: Experimental environment for measuring efficiency of protocol on Bus topology. The arrangements of nodes and their sequential alignment are designed to demonstrate the dynamic behavior of token-based or contention-based protocols, such as Token Bus and CSMA/CD (Carrier Sense Multiple Access with Collision Detection) [20]. These protocols govern how nodes access the shared channel, manage transmission priorities, and handle collision scenarios. The simulation operates with a time step of 2.0 milliseconds, enabling detailed observation of packet exchanges and protocol timing. Such visual simulations are critical for evaluating real-time constraints, bandwidth utilization, and network load--factors that directly impact protocol selection in DCS and other industrial network environments. To evaluate the performance of the system, a network topology simulation was conducted using NS2. In parallel, additional metrics and evaluation strategies were considered to gain deeper insights into the system's operational efficiency. The resulting performance outcomes and their implications are discussed in detail in Figure 7.  
In this case, there are various metrics used for system performance evaluation, including throughput, latency, jitter, packet loss rate, CPU utilization, memory utilization, delay variation, bandwidth utilization, response time, and bit error rate [21; 22]. Among these, we selected _throughput_ as the primary metric to objectively evaluate the system's performance in a quantifiable manner. Figure 7 illustrates a comparative analysis of aggregate throughput over time between two bus topology protocols: CSMA/CD (Carrier Sense Multiple Access with Collision Detection) and the Token Bus protocol. The \(x\)-axis represents time in seconds (ranging from 0 to 5 s), while the \(y\)-axis denotes aggregate throughput in bytes, indicating the total amount of data successfully transmitted across the network.