This read-only counter, in packets, tallies RADIUS packets received from this accounting server on the accounting port that were dropped for reasons other than being malformed, having a bad authenticator, or being an unknown type, in this deprecated IPv4-only table. Admins use it as a catch-all indicator of accounting packet loss from a given server that isn't explained by the other, more specific error counters. For example, a rising count here alongside otherwise-healthy request and response counters points to some other local processing issue discarding valid-looking accounting responses.