A network device having a system performance measurement unit employing one or more global time stamps for measuring the device performance is disclosed. The device includes an ingress circuit, a global time counter, an egress circuit, and a processor. The ingress circuit is configured to receive a packet from an input port while the global time counter generates an arrival time stamp in accordance with the arrival time of the packet. The egress circuit is capable of forwarding the packet to other network devices via an output port. The processor, in one embodiment, is configured to calculate packet latency in response to the arrival time stamp.