Non-intrusive mechanism to measure network function packet processing delay

A network device performs operations comprising: receiving a first plurality of data packets, each data packet of the first plurality of data packets including a checksum value, and storing the checksum values of a subset of the first plurality of data packets along with a first timestamp; providing the first plurality of data packets to a network function (NF); receiving, from the NF, a second plurality of data packets generated by the NF in response to the first plurality of data packets, each data packet of the second plurality of data packets including a checksum value; storing a second timestamp when checksum values of a subset of the second plurality of data packets match the stored checksum values; and generating telemetry data based on the first timestamp and the second timestamp.