This read-only PerfCounter64 counts 64-octet frames received on this link aggregation group as retained in the history bin, the smallest valid Ethernet frame size. A high proportion of this bucket in the LAG's traffic mix tells an administrator the link is carrying a large volume of minimum-size frames, such as TCP acknowledgments or keepalives, rather than bulk data. For example, an unexpected surge in cmLagHistoryESP64 could indicate a misbehaving application generating excessive small control packets over the LAG.