cvs commit: src/sys/netgraph ng_pptpgre.c

Gleb Smirnoff glebius at
Fri Feb 2 09:45:23 UTC 2007

glebius     2007-02-02 09:45:23 UTC

  FreeBSD src repository

  Modified files:
    sys/netgraph         ng_pptpgre.c 
  Quoting Alexander:
    Formulas described in RFC require high precision of floating point.
    Formulas of integer math implemented in ng_pptpgre give mistake in range
    of +0-7ms on RTT and +0-3ms on deviation. This leads to significant
    underestimation of real packet RTT.
    I have made a very simple patch to reduce mistake to +4-3ms on RTT and
    +2-1ms on deviation. Mistake in RTT is not good, but gets covered by
    deviation. To cover worst possible negative mistake in deviation I have
    added 2ms to it. Also this 2 ms cover the case when measured deviation
    is so small (about zero) that it can interfere with process scheduling
    delays or weather on Mars.
    My tests show decreasing of packet losses on 20ms RTT link from 2.5% to
    0.3% while speed increased un 1/3.
  Reviewed by:    archie
  Revision  Changes    Path
  1.40      +5 -4      src/sys/netgraph/ng_pptpgre.c

More information about the cvs-src mailing list