Ethernet packet time stamping techniques for real time performance assessment
ELT RTCs use an internal network based on standard ethernet. Assessing the performance of an RTC implies being able to measure when ethernet frames are sent by wavefront sensors and when frames are received or sent by the HRTC nodes. In this talk we present 3 different tools we use at ESO to timestamp ethernet traffic:
- ERSPANv2 is a feature of the recommended switches for RTCs; ERSPANv2 creates a copy of received and / or sent frames by the switch and adds a timestamp in the encapsulation header,
- The native hardware timestamping capability of certain generic-purpose network adapters,
- A PCI Express adapter from Napatech specifically designed for network capture.
We present these tools from the user perspective: the poorly documented information needed to parse the ERSPAN headers, the PTP requirements and command line options to activate hardware timestamping using tshark or tcpdump, and a few hints to get started with the Napatech.
Thomas Grudzien, ESO