This article helps to explain how different types of loss % calculation is done in PAA for TWAMP Monitor/Test execution.

TWAMP monitor settings and how threshold works:

Far end loss:  Packet Loss in the path from Sender to Reflector.

Near End loss: Loss in the path from Reflector to Sender agent.

Round-trip Loss: New parameter launched to track Overall loss for a packet from Sender to Receiver and back to Sender.. This value is not Far end + Near end, but overall has different metric calculation in backend to handle.

There are situation where customers can only see Round-trip loss but not Far End or Near End losses. This is possibly because PAA reports far/near end losses when it has the sufficient data available.

But in periods where PAA do not get any response at all (100% loss), the loss direction is not known. In this situation PAA delays the reporting up to 10s, but if there is no response before that then PAA will only report what is known, i.e. that there was round trip-loss.