A packet sending method of a controller includes obtaining a forwarding latency requirement of a service flow and a destination address of the service flow; determining a forwarding path that meets the forwarding latency requirement, and determining a number of a first cycle time in which an ingress node forwards a packet and a number of a second cycle time in which an intermediate node forwards the packet; sending a first entry to the ingress node that includes a sequence number of the packet and the first cycle time number; and sending a second entry to the intermediate node that includes the sequence number of the packet and the second cycle time number.