HOTS: An OWAMP-Compliant Hardware Packet Timestamper

Accurate timestamps on both the sender and the receiver side are crucial for one-way delay (OWD) measurements. Traditionally, the methods of (i) peering with NTP servers, and (ii) connecting to a time source directly, have been used to maintain the accuracy of a measurement system clock. However, it has became clear that such methods suffer from errors to different extents. In this paper, we introduce the hardware OWAMP [1] timestamper (HOTS), which generates extremely precise clock information for OWAMP test packets on both the sender and the receiver side. Compared with traditional methods, HOTS offers the following advantages: (i) the generated timestamp can be extremely precise because HOTS accepts an external 10-MHz signal as well as the 1PPS signal as input, and (ii) HOTS bypasses all of the software processing, thus minimizing possible errors. We also present the early results of OWD measurements that we made using this timestamper. DAG [2] is a similar measurement instrument which also uses hardware to generate timestamps for a packet. However, this product is only designed to record the arrival timestamp of a packet and cannot be used to measure OWD.