This read-only Unsigned32 (0 to 4294967293, in frames) defines how many frame errors must occur within the cienaCesOamErrFrameWindow, one second by default, to trigger an Errored Frame Event, per its description, defaulting to just one frame error. Because a single error within a one-second window is an extremely sensitive trigger, this default is meant to catch essentially any bit error on the link, and operators on links with a known nonzero baseline error rate typically raise it to avoid a continuous stream of alarms. An engineer managing a long-haul optical link with occasional single-bit errors from normal noise floor variation would raise this threshold above 1 to only alarm on a meaningfully elevated error rate.