What is Topology?
Topology refers to the way devices and connections in a network are organised or structured. In industrial and IT networks, topology determines how data moves between devices, such as PLCs, Sensors, HMIs, servers and field components.
There are both physical and logical topologies:
- Physical: how cables and devices are actually connected
- Logical: how data flows through the network
🔧 Common network topologies
| Topology | Description | Advantages | Disadvantages |
|---|---|---|---|
| Bus | All devices share a single common cable | Simple and inexpensive | A fault on the cable → entire network down |
| Star | All devices are individually connected to one central point (e.g. switch) | Easy to manage, flexible | Dependent on the central point |
| Ring | Each device is connected to two neighbours, forming a closed loop | Good fault detection, redundancy possible | More difficult to extend |
| Tree | Hierarchical network with several star structures on a backbone | Scalable and clear | More cabling, complex structure |
| Mesh | Each device is connected to several others (partial or full) | Very high reliability and redundancy | Expensive and complex |
| Line | One-to-one connections in a straight chain | Simple and inexpensive | If one connection fails, the rest go down |
🏭 Topology in industrial networks
In industrial automation, the choice of topology often depends on:
- System reliability
- Response time (Latency)
- Cost and cabling
- Scope for maintenance or expansion
Examples:
- AS-Interface → line or ring topology with simple flat cable
- PROFIBUS → bus structure with up to 126 participants per segment
- EtherCAT → line, ring or tree structure with high speed
- Ethernet IP or ProfiNET → usually star or tree via switches
🔄 Physical vs. logical topology
| Aspect | Physical topology | Logical topology |
|---|---|---|
| Definition | How devices are physically connected | How data flows behave |
| Example | Star with a switch | Logical ring through frame processing (e.g. EtherCAT) |
| Important for | Cabling, maintenance | Network behaviour, protocols, fault detection |
📌 In summary
Topology describes the structure of a network — how devices are connected and communicate. Choosing the right topology is crucial for the performance, reliability and scalability of industrial automation networks.