Diagnosis of POWERLINK networks using Wireshark

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Diagnosing POWERLINK networks using Wireshark is an effective way to identify and troubleshoot network problems. Wireshark provides detailed insights into network traffic and makes it possible to localize error sources quickly and precisely. This article describes the essential steps for installing, configuring and using Wireshark for POWERLINK diagnostics.

During startup, POWERLINK nodes follow a fixed pattern defined by their state machines. This process can be observed in detail with Wireshark, which is especially helpful to diagnose problems when a node does not switch to OPERATIONAL state. Understanding the individual start-up phases is crucial for precise error analysis but is not part of this article.

Information on POWERLINK and the start-up phases can be found in the technical documents and specifications on the B&R homepage.

Requirements for diagnostics with Wireshark

  • Wireshark installation (Download: Wireshark)
  • PC with a free Ethernet interface
  • An active POWERLINK network

Steps for diagnostics with Wireshark

  1. Preparation of the network interface
  • Deactivate all unneeded protocols (TCP/IP, Windows networks, etc.) in the network interface settings to avoid unwanted packets. These can interfere with the POWERLINK network.
  1. Connecting the PC to the POWERLINK network
  • To record data traffic, an Ethernet port of the PC is connected directly to the POWERLINK network at any point. Make sure that the network card is connected correctly and that the LEDs indicate the connection status.

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  1. Start the Wireshark recording
  • Open Wireshark
  • All detected interfaces are displayed on the start screen.
  • Select the network interface that is connected to the POWERLINK network.
  • Start the recording by double-clicking on the interface or via the blue Wireshark icon in the main bar.
  • The recording window then opens with the activities on the POWERLINK network.
  1. Analysis of the network recording
  • Sort the packets according to the “Time” column in order to recognize the recurring POWERLINK cycle.

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  • Note: Wireshark also offers the option of using color rules to color frames according to type. These color rules make it possible to distinguish different types of packets at a glance, which can make analysis much easier when used frequently. For example, SoA frames, ASnd frames and PRes frames can each be displayed in different colors to make it immediately visible which type of communication is currently taking place.
  1. Application of filters

  • Filters can be used to make the network recording clearer and only display certain frames or communication connections. There are two types of filters:

    • Display filters: These filters only affect the visibility of frames in a running or already saved recording. Examples are:
      • epl.src == 1 displays all packets sent by NodeID 1.
      • epl.dest == 1 shows all packets that are sent to NodeID 1.
    • Capture filters: These filters only capture packets that meet the filter criteria while they are being received. This allows the memory size of the recording to be reduced. Capture filters have a different syntax and are only recommended for experienced users.

  • Additional useful filters:
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    • Users can apply any number of other filters. These are just one example. These filters can also be saved in Wireshark’s filter and toolbar and can therefore be quickly reapplied with a mouse click for each new trace.
    • To visualize cyclical user data, you can also create a new column, for example, by selecting a PRes frame, right-clicking on “Payload” and selecting “Apply as Column”. Then rename the column to “PRes-Payload”.
  1. Hardware-supported network analysis
  • The use of a standard PC for network recordings is often unsuitable for fault diagnosis for several reasons:
    • Inaccurate timestamps: the timestamps of the recorded frames are often inaccurate as they are influenced by the interaction between the operating system and the network card. This is often only sufficient to correctly display the order of the frames, but not to determine the exact time of receipt.
    • Unmanageable file size: The file size of the recording can become impractically large.
    • Sporadic errors: The error occurs irregularly, which makes diagnosis more difficult.
    • Missing cause of error: The cause of the error may not be included in the recording period.
  • These shortcomings can be rectified with the X20ET8819 network analysis tool. It enables network recordings with high and reliable timestamp accuracy in the nanosecond range. In addition, digital inputs or filters can be used to start a recording, which is particularly useful for sporadic errors. This tool and the documentation can be obtained from the B&R homepage.
  1. Additional tips
  • If no connection is established between the POWERLINK network and the PC, the advanced settings of the PC network card should be checked. A hub can also be connected in between, as the physical connection does not require any settings here or is already correctly preconfigured.
  • Please note that user data in the POWERLINK network is transmitted in little-endian format.
  • Recommended network card settings:
    • Half-duplex
    • 100 Mbit/s transmission rate
    • Auto-crossover (optional)

By systematically applying these steps, most problems in the POWERLINK network can be efficiently diagnosed and rectified. Use the extensive possibilities of Wireshark to gain detailed insights into the network traffic and thus ensure the reliability and performance of your POWERLINK network.

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