receiving, by a second network device, a first packet sent by a first network device;

obtaining, by the second network device, a second packet in a target packet flow, a first dwell time period of the second packet on the first network device, and a second dwell time period of the target packet flow on the first network device based on the first packet, wherein the first dwell time period is a time difference between a first moment at which the second packet enters a queuing system of the first network device and a second moment at which the second packet is sent by the first network device after being queued in the queuing system of the first network device;

determining, by the second network device, a time difference between the second dwell time period and the first dwell time period, wherein the time difference is an active delay time period of the second packet on the second network device;

obtaining a third dwell time period of the second packet on the second network device, and obtaining a fourth dwell time period of the target packet flow on the second network device, wherein the third dwell time period is a time difference between a third moment at which the second network device ends an active delay of the second packet and a fourth moment at which the second packet is sent by the second network device after being queued in a queuing system of the second network device;

encapsulating the third dwell time period, the fourth dwell time period, and the second packet, to obtain a third packet; and

sending, by the second network device, the third packet to a next-hop network device of the second network device on a core network transmission path of the target packet flow after the first packet received by the second network device reaches the active delay time period and is queued in the queuing system of the second network device.