This 16-byte octet string captures the destination and source SMDS addresses of the last PDU that triggered the 'Src Ia Scrn Fail' violation, meaning the source individual address failed the switch's screening check -- the address exists and is valid but isn't authorized to originate traffic on this port. An admin decoding the source half of this pair can identify a device sending SMDS traffic from an address that isn't the one provisioned for this specific port, a common symptom of address spoofing or a misconfigured CPE. For example, a customer accidentally reusing another site's SMDS address on a new router would trip this violation as soon as it started sending traffic.