This is the count of correctly checksummed SCTP packets received for which this device could not identify a matching association, so-called out of the blue packets. A steady trickle can be normal, such as late packets arriving after an association was already torn down, but a sustained high rate suggests either a peer that still has stale associations this device has already closed, or unsolicited traffic hitting the SCTP port. A burst of these packets right after this device reboots is expected, since peers keep sending on associations that no longer exist locally until they too time out.