Abstract: A traffic generator may include a scheduler to provide packet forming data defining a packet; a background engine to retrieve a packet template, the packet template including a first checksum mask, a first pre-sum, and a first address; a fill engine to generate content for variable-content fields of the packet for a payload portion of the packet in accordance with the packet forming data and the packet template; and a checksum engine. The checksum engine may include an accumulator that calculates a payload checksum for the payload portion of the packet and first logic circuits that compute a first checksum based on the first pre-sum, the first mask, and at least some of the payload checksum and the variable-content fields. Insertion logic may insert the first checksum into the packet at a position indicated by the first address.