[ntp:hackers] Further to the timestamping issue
David L. Mills
mills at udel.edu
Sat Jun 14 21:31:50 UTC 2008
Not to bring up a dead horse, but I don't think everybody was completely
happy about the timestamp capture issue; at least, I have few comments
about the white paper Stuart Venters and I prepared. However, and mainly
to clear the air with a practical, worked-out scheme, I have updated the
NTP On-Wire Protocols briefing at
white paper http://www.eecis.udel.edu/~mills/onwire.html to fix a few
types, cleanup the presentation and add an interleaved broadcast mode.
For yucks I included a short description of the NASA/JPL Proximity-I
timestamping scheme used on Mars orbiters and landers. Cool.
For reference, the symmetric/broadcast interleaved protocol is backwards
campatible with the present protocol, resists lost, duplicate and bogus
packets and automatically adapts to basic and interleaved protocol
modes. It has been thoroughly tested in simulation for both normal and
If I can figure a way to capture TSC/PCC contents in the Ethernet
driver, this puppy will bark. I've peeked at the FreeBSD Ethernet device
driver for the Digital Tulip (if_de.c) and found it vaguely readable.
I'm not a device driver guru by any means, , although I feel like an
elephant in a china shop. The idea is to append the TSC to the end of
the receive and transmit buffer when the frame is complete. Crude, but
this is an expereiment, not a specification proposal. I have a couple of
machines with Broadcom NICs that the if_de.c driver can handle.
Comments and/or guffaws humbly accepted.
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