Precision timestepping of network packets

When recording network traffic, accurate timestamping of the arrival of packets is essential for the subsequent analysis of performance metrics. Until the mid-1990s using off-the-shelf network interface cards and computer clocks proved sufficient. With the introduction of ever increasing link data rates the task of proper timestamping becomes increasingly important for continued network research. In the past five years the Dag development team in the WAND research group has undertaken substantial efforts to meet those demands and in this paper we discuss the advantages and limits of this new, hardware driven approach and explain how to interpret high precision timing information for packet arrivals.