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I would assert that, given two status bits, the PING bits are redundent, as the far end state is known from the status bits. An explicit ping is not required. Even with OAM in frames there is an implied ping every 200ms. See the pdf file on my loop back email for the (crude) state machine.
If the far end is up and receiving OAM status from the near end system then the status bit is 1
If the far end is up and not receiving OAM status from the near end system then the status bit is 0.
If the far end isn't up then there is no OAM message going from it.
The near end system could also use 01nn as a minor alarm signal, 10nn being major alarm.
So, if we have two bits for status and two bits for loop back that still leaves four bits for other conditions e.g. downsteam alarm conditions (probably two) and two bits for implementation specific.