2018-01-19 10:10 GMT+01:00 Guy Harris <g...@alum.mit.edu>: > On Jan 4, 2018, at 5:47 AM, Bruno Verstuyft <bruno.verstu...@gmail.com> > wrote: > > > are any more clarifications needed for the XRA header spec? > > How is the Symbol ID used for timing calculations? >
DOCSIS 3.1 PLC (PHY Link Channel) frames in the downstream contain an absolute timestamp. For every packet in the downstream, the difference in symbols between the previous PLC frame and the packet is calculated. With the help of parameters from the OCD (discrete fourier transform size and cyclic prefix), this difference in symbols can be converted in a difference in nanoseconds. This time difference is then added to the absolute timestamp of the previous PLC frame, which yields the absolute timestamp of the packet. This timestamp is stored in the timestamp of the pcap packet header. For debugging reasons, the symbol id TLV can also be added to the packet. > > Is the Burst ID just a sequence of octets? > For the moment, the Burst ID is a uint64_t. Should this not be not enough in future implementations, it can be increased to e.g. uint128_t > What does the Burst ID Reference field contain? Another burst ID? The Burst ID reference is the same as the Burst ID. Burst IDs are used in databursts, while Burst ID references are used in Mac Frames. For the moment, these are both uint64_t. _______________________________________________ tcpdump-workers mailing list tcpdump-workers@lists.tcpdump.org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
