Glossary · Industrial communication
Line topology
Also known as: Daisy-chain topology, Linear topology
German: Linientopologie
In industrial communication, a line topology is a network structure in which devices are connected one after another, each device forwarding traffic to the next, typically through an integrated two-port switch. It is common in Industrial Ethernet systems such as PROFINET and EtherCAT.
- Industrial communication
In one sentence
A line topology connects devices one after another, each forwarding traffic to the next, as is common in Industrial Ethernet.
Example
Six PROFINET drives along a conveyor are daisy-chained from one to the next, so only one cable runs from the control cabinet to the first drive.
How it applies
- Engineering: Line topologies save cable and follow the physical layout of machines. The number of devices in a line adds forwarding delay, which designers check against cycle time requirements.
- Operation: If a device fails or loses power, all devices behind it lose communication. Closing the line into a Ring topology with a redundancy protocol such as Media Redundancy Protocol (MRP) avoids this single point of failure.
- Maintenance: Replacing a device interrupts the line. Maintenance instructions should say which parts of the machine stop communicating during the replacement.
- Documentation: The documentation team shows the line order in the network drawing, marks port numbers (in and out) and explains the consequences of interrupting the line.
Line topology vs. bus topology
In a Bus topology all devices share one passive medium. In a line topology each link is a separate point-to-point Ethernet connection, and the devices actively forward traffic. Drawings look similar, but failure behavior differs.