This counter tracks how many packets received from the remote client on this session were discarded by the VPN gateway during processing, rather than successfully handled. A nonzero and climbing value here, especially relative to crasSessionInPkts, tells an admin that this particular session is experiencing packet loss inside the appliance itself - a sign of resource exhaustion, MTU/fragmentation issues, or a malformed traffic stream from that specific client. For example, a session showing 500 drops out of 2 million received packets points to an occasional decode or buffer issue rather than a healthy tunnel.