Switch – Non-PTP compliant switch

switch

Given a non-PTP switch (e.g. no hardware support for time stamping), how can one make it to be as close as possible to a PTP compliant switch. I am thinking here to configure the switch such that the PTP traffic has the highest priority (which is kind of super basic configuration). Can you please suggest other possible configurations?

PS: I am aware that in general such configurations are hardware dependent given the switch capabilities. Therefore I am looking for all kind of crazy options.

Best Answer

How about using a hub rather than a switch?

It might be a stretch since your question has "switch" right there in the title, but you did say:

Therefore I am looking for all kind of crazy options.

Using a hub would avoid the jitter induced by the switch's queue.

I just ran a test where I measured the maximum offset after convergence between two PTP devices first on an unmanaged switch, and then on a hub.

  • Unmanaged switch: ~450ns
  • Hub: ~50ns

As you can see, nearly an order of magnitude improvement.

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