What is MRP?
MRP stands for Media Redundancy Protocol and is an industry-specific network protocol that provides fast redundancy in ring topologies based on Ethernet. The protocol is standardised in IEC 62439-2.
MRP is widely used in OT networks where minimal downtime and deterministic behaviour are crucial — for example in production, process and transport automation.
🧠 How does MRP work?
- MRP operates in a ring structure of switches or devices with Ethernet ports
- One switch acts as the MRP Manager (Ring Manager); the others as MRP Clients
- Under normal conditions one port is blocked to prevent a network loop
- In the event of a cable or port failure, the ring is automatically restored and the blocked port is activated
- Recovery time is typically <200 ms, depending on configuration and number of nodes
MRP is specifically designed for real-time industrial communication such as ProfiNET.
🏭 Application of MRP in industrial networks
- Redundant communication between PLCs, SCADA, HMIs and Drives
- Ring topologies in production halls, water treatment plants or traffic systems
- Minimal downtime in case of cable breaks or switch failures
- Frequently used in combination with Industrial Ethernet, ProfiNET or Modbus TCP
- Compatible with industrial switches from vendors such as Siemens (SCALANCE), Hirschmann and Phoenix Contact
MRP is optimised for deterministic networks with strict availability requirements.
🔍 MRP vs. RSTP vs. PRP
| Aspect | MRP (Media Redundancy Protocol) | RSTP | PRP (Parallel Redundancy Protocol) |
|---|---|---|---|
| Recovery time | <200 ms | 1–10 sec | 0 ms (traffic always sent in duplicate) |
| Topology | Ring only | Flexible (ring, mesh) | Dual networks (parallel) |
| Complexity | Moderate | Low | High |
| Use in OT | Widely used for real-time OT networks | Common for standard redundancy | Used for critical installations with zero loss |
🔐 Security considerations
- MRP traffic is not encrypted — protect configuration interfaces via RBAC and ACL
- Use Port Security to keep unwanted devices out of the ring
- Monitor status changes and reconfigurations via SNMP or Syslog
- Integrate with SIEM for detecting unwanted topology changes
- Protect the ring manager switch against physical and logical access
A compromised ring manager can disrupt all communication — provide segmentation and logging.
📌 In summary
MRP is an OT-specific protocol that enables fast failover in ring topologies, without broadcast storms. It is broadly accepted in industrial networks where availability and reliability are vital.