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Media Redundancy Protocol

Media Redundancy Protocol is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Media Redundancy Protocol rather than just read about it. In short: Media Redundancy Protocol (MRP) is a data network protocol standardized by the International Electrotechnical Commission as IEC 62439-2. It allows rings of Ethernet switches to overcome any single failure with recovery time much faster than achievable with Spanning Tree Protocol.

Media Redundancy Protocol — main illustration
Media Redundancy Protocol — illustration

Key takeaways

  • Media Redundancy Protocol belongs to computer science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Media Redundancy Protocol to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Media Redundancy Protocol from memory before moving on to harder problems.

Reference excerpt

Media Redundancy Protocol (MRP) is a data network protocol standardized by the International Electrotechnical Commission as IEC 62439-2. It allows rings of Ethernet switches to overcome any single failure with recovery time much faster than achievable with Spanning Tree Protocol. It is suitable to most industrial Ethernet applications.

Properties MRP operates at the data link layer (OSI Layer 2) of Ethernet switches and is a direct evolution of the HiPER-Ring protocol developed by Hirschmann in 1998. Hirschmann is now owned by Belden. MRP is supported by several commercial industrial Ethernet switches. In an MRP ring, the ring manager is named Media Redundancy Manager (MRM), while ring clients are named Media Redundancy Clients (MRCs). MRM and MRC ring ports support three statuses: disabled, blocked, and forwarding:

Disabled ring ports drop all the received frames. They also do not send any frames. Blocked ring ports drop all the received frames except the MRP control frames. They also do not send any frames except MRP control frames. Forwarding ring ports receive all frames and also forward the received frames. During normal operation, the network works in the Ring-Closed status (Figure 1). In this status, one of the MRM ring ports is blocked, while the other is forwarding. Conversely, both ring ports of all MRCs are forwarding. Loops are avoided because the physical ring topology is reduced to a logical line topology. In case of failure, the network works in the Ring-Open status (Figure 2). For instance, in case of failure of a link connecting two MRCs, the MRM sets both of its ring ports to the forwarding state; the MRCs adjacent to the failure each have a disabled port (because of the link loss) and a forwarding ring port; the other MRCs have both ring ports forwarding. Also, in the Ring-Open status, the network logical topology is a line.

Frame structure MRP information is sent in the form of an Ethernet frame, with the EtherType field set to 0x88E3. The frames are built by Type–length–value (TLV) structures, allowing organizationally specific information.

Standards The International Electrotechnical Commission standard for MRP was published in 2010 as IEC 62439-2 and amended in 2012. The standard IEC 62439 published in 2012 also defined the following protocols:

Parallel Redundancy Protocol (PRP) Cross-network Redundancy Protocol - CRP Beacon Redundancy Protocol - BRP High-availability Seamless Redundancy (HSR) With the settings specified in IEC 62439-2, MRP guarantees a worst-case recovery time of 500 ms, 200 ms, or 30 ms in rings composed of up to 50 switches, and a worst-case recovery time of 10 ms in rings composed of up to 14 switches.

See also Fieldbus

References

Illustrations

Media Redundancy Protocol: Figure 1: MRP ring in Ring-Closed status
Figure 1: MRP ring in Ring-Closed status
Media Redundancy Protocol: Figure 2: MRP ring in Ring-Open status
Figure 2: MRP ring in Ring-Open status

Worked examples

Example 1 — a first encounter with Media Redundancy Protocol

Start with the simplest possible case. Write down what Media Redundancy Protocol claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Media Redundancy Protocol before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Media Redundancy Protocol ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Media Redundancy Protocol

In research
Media Redundancy Protocol appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Media Redundancy Protocol in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Media Redundancy Protocol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Industrial Ethernet, Network protocols, Networking standards, so understanding it makes those chapters shorter.
In everyday life
Look for Media Redundancy Protocol outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Media Redundancy Protocol in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Media Redundancy Protocol means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Media Redundancy Protocol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Media Redundancy Protocol in simple terms?

Media Redundancy Protocol (MRP) is a data network protocol standardized by the International Electrotechnical Commission as IEC 62439-2. It allows rings of Ethernet switches to overcome any single failure with recovery time much faster than achievable with Spanning Tree Protocol.

Why does Media Redundancy Protocol matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Media Redundancy Protocol?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Media Redundancy Protocol.

Tags

  • Industrial Ethernet
  • Network protocols
  • Networking standards

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