This value specifies the length, in bytes (64 to 1500), of the data sent in an Eth-test frame; the actual content is determined by tmnxDot1agCfmMepEthTestPattern. An admin sets a larger data length to more closely simulate production-size frames when testing for bit errors across a path. Choosing a length close to the service's typical frame size gives a more representative test than the smallest allowed value.