Abstract: Aspects of a high-precision packet train generation process are distributed among several distinct processing elements. In some embodiments a control processor configures a packet-processing unit with a packet train context that includes details such as the number of packets to be generated and the headers to be included in the packets. The packet-processing unit takes a packet to be used in the packet train and recirculates it a number of times, as specified by the packet train context. The recirculated packets, with the appropriate headers inserted, are forwarded to a traffic-shaping queue in queuing hardware. The traffic-shaping queue is configured to output the forwarded packets with a constant inter-packet gap. Thus, the generation of the multiple packets in the packet train is handled by the packet-processing unit, while the precise inter-packet timing is provided by the traffic-shaping queue in the queuing hardware.