Do you know how the MRP protocol for industrial environments? As specialists in industrial communications consulting We'll tell you everything you need to know—and then some—about how it works.

¿Qué es MRP?

EL protocolo MRP o Media Redundancy Protocol It is described in the IEC 62439-2 standard. It is used in high-availability environments in industrial networks.

This MRP protocol will operate at Layer 2 and is specifically designed for ring networks with up to 50 devices. This ensures deterministic behavior at all times when a state change is required.

How does the MRP protocol work in industrial environments?

Route Change Times

To make this possible, maximum time limits are set for when communications must be restored, based on the selected configuration. The time limits have maximum values of 10, 30, 200, and 500 ms, and packet routing changes typically occur between 50% and 75% faster.

Nodos

Nodes are an important part of the MRP protocol. In this configuration, each node has two links in the ring. One will be designated as the MRM (Media Redundancy Manager), which will monitor and control the system and take action in the event of a failure.

To do this, it will send control frames from each port, which will be received at the other end, even if some ports are blocked.

MRC

The MRC o Media Redundancy Client consists of the remaining ring elements. The MRM sends control frames and the MRC It forwards them between ports to detect any errors that may exist and connect the blocked port.

The control loops are:

• The ones that monitor the ring's status. These are test frames sent over both ports connected to the ring.
• Those that detect failures and restore links through topology changes.
• Those that switch links when a failure is detected or to recover a port.

How does all this work?

With a closed ring, the MRM should block traffic—except for these frames—with the ring behaving as a single link, without any loops.

An open ring occurs when the MRM does not receive frames from the other end, interpreting this as a link failure. The blocked port sends frames as usual.

The MRC, for its part, reports changes in the status of the links; therefore, in the event of an open loop, the MRC will send a control frame to notify the MRM.

Both MRC and MRM define four states for their ports. These are:

• Disabled: All plots are ruled out, without exception.
• Blocked: All frames are discarded except for MRP control frames and other protocol frames.
• Forwarding: Forward all frames.
• Not Connected: Broken or disconnected link.

Uso de los protocolos MRP

Each manufacturer can provide different functionalities protocols. For example, Siemens Total Integrated Automation It offers the ability to integrate the protocol with management software.

You can also Define multiple MRP rings for a single VLAN or interoperability is achieved, among many other features.

It is also important to remember and take into account both recommendations and limitations when configuring equipment, since improper handling will render these protocols completely useless.