This Counter32, keyed by the ATM link index, counts F4 flow segment-level OAM cells — the standard ITU-T ATM virtual-path-level operations/maintenance cells exchanged between adjacent segment endpoints — with the source DESCRIPTION left blank so the meaning follows the standard ATM F4 OAM flow implied by the object name. Admins use F4 segment cell counts to confirm that VP-level OAM continuity checking and alarm signaling is actively running on a segment of this ATM link. For example, an unexpectedly low or zero count here on a link expected to be actively monitored would suggest F4 OAM has stopped being generated or received on that segment.