This is the DCE-side counterpart to lportDTEInErrorFrames, counting LMI frames received by the DCE role that contained protocol errors rather than well-formed poll or status exchanges. An admin watches this specifically when the port is acting as DCE, the network side, to spot a misbehaving customer DTE device sending malformed LMI messages. For example, a rising lportDCEInErrorFrames count on a port serving a particular customer's router, while other DCE ports on the same shelf stay at zero, points suspicion squarely at that customer's CPE.