This 16-byte octet string captures the destination and source SMDS addresses of the last PDU that triggered the 'Da Type Invalid' violation, meaning the type field encoded within the destination address was set to an invalid value. An admin decoding the destination half of this pair can identify traffic that's addressed with a malformed destination-type indicator rather than simply an unreachable or unauthorized address. For example, a device attempting to send a PDU with a destination address type that doesn't match any valid individual or group encoding would trigger this violation with that malformed field visible in the captured header.