Re: [tcpdump-workers] Request for link-layer header type (XRA)
On Jan 4, 2018, at 5:47 AM, Bruno Verstuyft wrote: > are any more clarifications needed for the XRA header spec? How is the Symbol ID used for timing calculations? Is the Burst ID just a sequence of octets? What does the Burst ID Reference field contain? Another burst ID? ___ tcpdump-workers mailing list tcpdump-workers@lists.tcpdump.org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Re: [tcpdump-workers] Request for link-layer header type (XRA)
2018-01-19 10:10 GMT+01:00 Guy Harris : > On Jan 4, 2018, at 5:47 AM, Bruno Verstuyft > 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
Re: [tcpdump-workers] Request for link-layer header type (XRA)
On Jan 19, 2018, at 5:03 AM, Bruno Verstuyft wrote: > 2018-01-19 10:10 GMT+01:00 Guy Harris : > >> 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 So it should be treated as an opaque array of bytes, with no significance to the values of the bytes, and used only for matching bursts and the MAC frames contained within them by comparing the byte arrays for equality? >> 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. I.e., one or more MAC frames can be transmitted in a burst, and a capture can contain a record for a burst as well as records for the MAC frames within the burst, with the record for the burst having a Burst ID parameter, and all the records for the MAC frames in that burst have a Burst ID Reference parameter containing the burst ID value for the burst in which it appeared? ___ tcpdump-workers mailing list tcpdump-workers@lists.tcpdump.org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
