What is Ring Redundancy?
Ring redundancy is a network topology in which network components (such as Switches) are connected in a ring structure. This means that data can travel in two directions, so that if a cable or device fails, communication is automatically continued via the other side of the ring.
In industrial automation, ring redundancy is essential for high availability and fault tolerance, with minimal recovery time.
🧠 How does ring redundancy work?
- Devices are connected together in a closed loop (ring)
- In normal operation, one connection is passive or blocked to prevent network loops
- If a cable or device fails, the ring is automatically healed by activating the blocked port
- Recovery time depends on the protocol:
Ring redundancy guarantees continuous network access for critical systems such as PLCs, SCADA and HMIs.
🏭 Use of ring redundancy in industrial networks
- Factory floors with line production or process plants
- Network structures for Drives, Remote IO, HMIs, Sensors and Actuators
- Substations in the energy sector (often with IEC 61850 + GOOSE)
- Use of robust industrial Switches supporting MRP or DLR
- Backbone structures at Purdue Model levels 1–2 (process and field level)
Ring structures are often combined with VLAN, QoS and Firewalls for additional security and segmentation.
🔍 Comparing ring redundancy protocols
| Protocol | Recovery time | Topology | Use |
|---|---|---|---|
| MRP | <200 ms | Single ring | Common in industrial networks |
| DLR | <3 ms | Ring, device-based | Ethernet IP environments |
| RSTP | 1–10 sec | Flexible | Basic redundancy |
| PRP | 0 ms | Parallel networks | Critical OT systems |
🔐 Security considerations
- Ring structures are vulnerable to broadcast storms without proper management
- Protect the configuration via RBAC, ACL and physical access control
- Use SIEM and network monitoring to detect changes or faults in the ring quickly
- Segment logical networks via VLAN
- Apply Port Security on access ports
An uncontrolled change in a redundant ring can cause network loops or downtime.
📌 In summary
Ring redundancy is a robust networking solution that increases availability and reliability, especially in industrial environments where outages are unacceptable. By using protocols such as MRP, DLR or PRP, communication remains active during faults or interruptions.