Clock synchronization NIC offload

In one embodiment, a system includes a network interface controller including a device interface to connect to a processing device and receive a time synchronization marker message from an application running on the processing device, a network interface to send packets over a network, and packet processing circuitry to process the time synchronization marker message for sending via the network interface over the network to a slave clock device, generate a time synchronization follow-up message including a timestamp indicative of when the synchronization marker message egressed the network interface, and process the time synchronization follow-up message for sending via the network interface over the network to the slave clock device.