This field reports the total number of packets received that were less than 64 octets in length (excluding framing bits but including FCS octets) and had either a bad Frame Check Sequence (FCS) with an integral number of octets (FCS Error) or a bad FCS with a non-integral number of octets (Alignment Error), exposed here as cienaCesPmExtendedTxRxStatsBinFragmentsPkts. On this Ciena CES port's PM data, this counts frames that are both under 64 octets AND carry a bad FCS or alignment error — true collision fragments — which is the classic symptom of a duplex mismatch or a noisy shared/half-duplex segment feeding this port; and this sits in the currently active extended Tx/Rx interval bin — its sibling StartTime/ClearTime fields mark exactly which window is being counted, so a change here reflects activity happening in the live collection interval, not something already filed away in history. For example, a healthy port would sit at 0 for collision-fragment frames in this bin; even 1 is enough to warrant a look, since this class of counter isn't supposed to move under normal operation.