On Wed, Dec 28, 2011 at 21:54, David Malone <[email protected]> wrote: > Modern hardware that supports 802.11e (or 802.11n, which requires > much of the QoS part of 11e) can control things like the number of > retries, and you could hack the driver to inspect the packets and > if it is NTP to reduce the number of retires.
I recognize I'm suggesting a layer violation in wishing 802.11 devices treated UDP differently from TCP, or even worse in terms of layer violation, UDP 123 differently from UDP 53. It's not pretty, but it would make a positive difference. The ideal number of retries for NTP may be zero, assuming the radio layer loss rates are less than 87.5% in practice. > An alternative would > be to use NTP's broadcast mode on a LAN, which would eliminate > retries. Right. > However, I suspect that bufferbloat and asymetric delays > on DSL is probably a much bigger problem for NTP than 802.11 retries. Absolutely. Nearly every consumer broadband connection has bufferbloat issues. Local loop asymmetry is extreme with ADSL. And most NTP clients in the wild are using NTP servers reached over an asymmetric WAN connection. Reverse and forward delay will frequently be slightly different, introducing apparent offset error. Cheers, Dave Hart _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
