After making a PTP measurement with Sentinel, it is possible to load the captured Packet Delay Variation data as an impairment pattern in Paragon-X, meaning, for example, that it is possible to ‘replay’ network conditions back in the lab to test equipment behaviour and perform further analysis.

The process to do this is below.

Sentinel Capture

  1. Make a PTP measurement with Sentinel and save it to the instrument.

  2. Transfer the files from the Sentinel:

    1. The files required are the PDV captures: xxxx_FWD_PDV.dset and xxxx_REV_PDV.dset.

    2. The FWD file is the PDV for T1 (Sync) Messages. The REV file is the PDV for T4( Delay Request) messages.

    3. The captures can be transferred off the Sentinel using the procedure here:Sentinel: Getting Capture Files and Logs

Create Paragon-X PDV Replay Files

  1. Open CAT and load the Sentinel capture file(s)

  2. Navigate to “Select Metrics” and check the “PDV” measurements:

  3. Navigate to “Export”. Choose the message type (Sync or Delay Req) ensure the “PDV” data is selected, select “PDV Replay” from the drop-down menu and press “Export Data”.

  4. Repeat for the other message type if required.

  5. When the file has been exported it can be viewed and transferred as required.

Replay on Paragon-X

To apply the PDV delays:

1. Non MSE Mode

 

 

2. MSE Mode

Selecting Sync will mean that delays will be applied to Master 1 Tx and Delay Request will be applied to Master 1 Rx.

 

The Paragon-X applies impairment values to each packet sequentially with no adjustment for packet rate. This means that in order to ensure the replayed PDV is consistent with what was captured, the packet rate of the original captured data should be used when applying impairment.

For example, if the data on Sentinel was captured at 16pkt/s then the Paragon-X MSE or the flows being impaired in thru-mode should also be 16 pkt/s.