US Patent 7925741 Black-box host stack latency measurement

A method comprises sniffing an input from a client device to a host device and an output from the host device to the client device; recording a first time parameter in response to a characteristic data unit being inserted into the input that is outputted from a host stack of a host device; recording a second time parameter in response to the output that comprises the characteristic data unit being received by the host stack; and measuring a latency based on the first time parameter, the second time parameter and arrival time of the input and the output at a sniffing point.