Standard Deviation of Token Round-Trip Time

Overview

• This shows how much the round-trip time of a token is changing.
• A larger number means more fluctuation in round-trip time.
• Large Standard Deviation shows problems that are inconsistent, changing every trip.
• Fail if: the fluctuation is more than 0.5ms.
• Warning if: the fluctuation is more than 0.1ms.

Why it fails

• Token disruptions, caused by:
• Bad wiring.
• Devices coming on and offline.
• A device that is speaking for a long time inconsistently.

How to fix it

• Check for token disruptions.
• If token disruptions, look for offline devices or check wiring.
• If no token disruptions, find the pair that have the longest standard deviation (sort Std. Dev. (ms) column).
• Most commonly the destination is not accepting it.
• Could also be that the source is chatty and holding the token too long.
• Check to ensure the destination is online, configured and wired properly.