This counts instances where a DXI2 frame received on this interface had an incorrect size, a check distinct from the field-level validation counters since it looks at overall frame length rather than individual header fields. An admin treats a rising count here as a sign the CPE may be sending frames that violate the DXI2 maximum or expected size, potentially due to an MTU misconfiguration on the customer's router. For example, a customer who recently increased their router's interface MTU beyond what the DXI2 encapsulation on this port supports would likely start driving up lportSmdsCntDxi2FrameSizeErrors.