Packet arrival time in 1588 for 40GE/100GE

1588 timestamping assumes a well-defined instant at which the beginning of a packet crosses the reference plane between the precision time protocol (PTP) node and the network. However, this definition is not clear in the case of a multi-lane serial bus such as 40GE/100GE. Furthermore, there is an implied time-ordering between the lanes of a serial bus that is not captured in the existing definition. This paper explores issues with multi-lane serial buses as it relates to time-stamping and proposes revised definitions for packet arrival time in the case of a serial bus.