This notification-only string identifies the switch port where a DoS attack was detected, formatted as just the port number in standalone mode or as "unit:port" in stack mode. It lets the receiving NMS pinpoint exactly which physical port to check or shut down without needing separate lookups. For example, a trap varbind of "2:3" tells the admin the attack was seen on port 3 of stack unit 2, whereas "23" would mean port 23 on a standalone switch.