Paragon-X: How do I use Through Mode (Option 260)?

Paragon-X can be used in through mode (i.e. connected in-between a Master port and a Subordinate port) to make measurements in situations where it is not being used to emulate a PTP Master or Subordinate. How do I configure and use this?

Method

Note: Through-mode captures are only possible for end-to-end PTP messaging. Peer-to-peer PTP is not currently supported.

Paragon-X may only have through-mode capability, or it may have a PTP Emulation option installed. In both cases, through-mode is enabled by selecting the 1588v2 Operating Mode and ensuring the checkbox (if available) is unchecked:

With MSE option:	With no MSE option:
Open	Open

In the Setup Interface screen, ensure that Thru Mode is selected in the Ethernet tab and that the SyncE Clock Rx → Tx box is ticked. Configure the interface parameters (line rate and media type) to match the connected network links.

Note: in through mode Port 1 and Port 2 must have the same configuration, so it is not possible to uncouple the settings to make independent settings for each.

In the References tab, ensure that a suitable external frequency reference is selected, and if Time Error measurements are required, that the external 1PPS reference is also selected:

If an external frequency reference is not selected, or the same reference is not used in the network being tested, an offset (drift) will be seen in the measurements (see Troubleshooting section below)

The 1PPS reference should be a common reference with/from the master clock that is generating the PTP timing flow at the network point that is being measured. Without this shared phase reference it is not possible to measure the time error of the received messaging and only PDV measurements will be available.

Using the Select Flow button, click the Capture Packets button and let it run for a few seconds (if a warning about active filters is displayed, click Yes to clear them), then stop the capture. The Flow Wizard button will then become available:

Click on this Flow Wizard button to view the analysis of the captured PTP flows:

As shown in the third image above, select the PTP flows of interest (i.e use the source and destination addresses to determine the PTP flows between the devices to be measured) then click Set. Close this window using the X in the top-right corner.

You can now confirm that the configuration so far matches the physical setup and that the filters are set: in the main P-X GUI window the Link, Good Pkts, Ref and 1PPS Ref indicators should all be green, and there should be SET indications against Flow Filter Flows:

If this is not observed, check settings and connections before continuing.

The bulleted settings listed below which are found in the Configure Capture window apply only to the data shown in the P-X GUI; analysis in CAT does not refer to these. However, to ensure that all data displayed in the GUI is correct, it’s good practice to configure these parameters to match the network being measured:

• 1-step or 2-step

• whether to include the correctionField value in the analysis

• Sync/Delay_request message packet rate

If Time Error measurements are required (and the shared 1PPS reference is available), check the relevant box and enter suitable cable delay compensation values (a value of 5ns per m of cable or fibre can be used):

A measurement can now be started by clicking the Start Capture button

A basic display of the capture data will be shown to indicate PTP capture is occurring. For further analysis, this should data be loaded into CAT using the Select Graph button or the Tools - Calnex Analysis Tool (1588v2) menu item:

If no Time Error Measurement option is shown, check that the 1PPS Ref indicator is green and Absolute Time Locking is enabled in your Configure Capture settings.

If no Time Error measurements are required or configured, the PDV option will be available in these same menus, which will allow analysis of the captured messaging PDV.

Analysis using CAT

Both Time Error and PDV results can be viewed in CAT, either in live capture mode as shown above, or ‘offline’ by importing a previous capture.

Analysis of both types of metric (TE and PDV) can be performed in the same CAT instance by selecting those required using the Select Metrics button. In this screen, clicking on the ? beside a metric type will display associated information and references. The desired metrics may be enabled by checking the box beside each, or a sub-set of a particular type chosen by expanding the dropdown menu:

After enabling additional metrics, click the Calculate button to process the data before using the View Results button to view the results.

Appropriate thresholds (limits) and masks may be applied to the various metrics, which enables a PASS/FAIL indication for each:

Troubleshooting

• The Time Error Measurement option is not available in the ‘send to CAT’ options

  • check your Configure Capture settings to ensure that Absolute Time Locking is enabled and that a valid 1PPS reference is configured and detected (i.e. the 1PPS Ref LED is green)

• The devices being measured are locked and stable but an offset (drift) is observed in the results as illustrated below (the slope may be either positive or negative):

  • check that a frequency reference shared with the network being measured is connected and configured on the Paragon-X

• The results are not as expected

  • ensure that the correct source and destination addresses for the measurement of interest have been selected in Flow Wizard, and that the direction of the messages is correct.

  • confirm the Include Correction Field and Packet Selection settings within CAT are correct, and that if a particular capture range is required, that the Data Analysis Range is suitable: