This Counter64 counts the number of good ESP encrypted packets processed on this Virtual Interface, per its description, the packet-level counterpart to the SA-level establishment counters above. An admin watches this as the primary throughput indicator for this specific protocol/direction combination, expecting it to climb steadily whenever the tunnel is actively carrying traffic. For example, an admin verifying that a newly built ESP tunnel on VI 3 terminating a partner site-to-site tunnel is actually carrying user traffic would confirm this good-packet counter is incrementing, not stuck at zero.