PTP and smpSynch Compatibility
ARSVIN separates two different ideas that are often mixed up during lab testing:
- PTP traffic visibility — optional lab traffic that helps you see PTP-like packets on the process-bus test network.
- SV
smpSynchbehavior — the value written inside the Sampled Values ASDU so a subscriber can decide whether it accepts the stream.
The built-in PTP traffic generator is for isolated lab experiments only. It is not a certified grandmaster and it is not evidence of calibrated time accuracy.
smpSynch behavior modes
| UI mode | SV value | Meaning inside ARSVIN |
|---|---|---|
| Global compatibility | 2 |
Marks the SV stream as globally synchronized so stricter subscribers can accept point-to-point lab traffic. This is compatibility behavior, not proof of real PTP accuracy. |
| Local compatibility | 1 |
Marks the stream as locally synchronized for subscribers that accept local lab synchronization. |
| Honest unsynchronized | 0 |
Publishes the stream as not synchronized. Use this when you want the frame to be semantically conservative. |
| External PTP auto | 0, 1, or 2 |
Derives smpSynch from observed external PTP health. If no valid PTP evidence is visible, ARSVIN does not claim global synchronization. |
Recommended default for point-to-point relay checks
For practical relay readability checks, use:
smpSynch: Global compatibility — smpSynch=2
PTP traffic: Off or LabPublisher, depending on what the target relay expects to seeThis mode exists because some subscribers reject SV streams that do not report synchronized status. The label intentionally says compatibility so it is clear that ARSVIN is helping the subscriber accept the stream, not certifying real time synchronization.
When to use External PTP auto
Use External PTP auto when the lab has a real external PTP source and you want ARSVIN to behave more conservatively.
In this mode, ARSVIN looks at observed PTP health and chooses the SV smpSynch value based on the current evidence. If no valid PTP evidence is visible, the stream falls back to unsynchronized behavior instead of silently claiming global sync.
Safety boundary
Compatibility modes are intended for isolated point-to-point testing, lab visibility checks, and process-bus experiments.
They should not be used as proof of:
- calibrated PTP accuracy
- relay timing performance
- protection trip-time acceptance
- FAT / SAT synchronization compliance