[ntp:questions] Re: abuse or bug ?

David Schwartz davids at webmaster.com
Fri Jan 28 03:25:18 UTC 2005

"Henk P. Penning" <henkp at cs.uu.nl> wrote in message 
news:Pine.GSO.4.44.0501270856030.14692-100000 at castor.cs.uu.nl...

>  it has been noted that some clients poll time servers at
>  a rate of 1 packet per second, for an unlimited period.


>  Is this a bug in the standard ntpd software

    Nobody has yet found the standard ntpd software to do this, as far as I 
know, you are the first to report it.

> or
>  abuse by bad software or badly configured clients ?

    So it seems.

>  The example below make me think it is a bug.
>  client   : (in cs.northwestern.edu)
>  hardware : Sun, SunBlade 150
>  operating system :
>    Linux gandalf 2.4.26-sparc-r2 #14 Wed Sep 22 15:27:12 CDT 2004 sparc64
>    sun4u TI UltraSparc IIe (Hummingbird) GNU/Linux
>  ntp      : ntp  4.2.0-r2
>  config :
>    server pool.ntp.org
>    driftfile       /var/lib/ntp/ntp.drift
>    restrict default notrust nomodify
>    restrict

    These 'restrict' lines will likely stop the server from being reachable.

>  It has sent 438851 packets in the last 129.3 hours to 'ntp.cs.uu.nl'.
>  The client says the server is unreachable.

    How confident are you in this number? It definitely seems strange. NTP 
should not poll a non-responding server more than once every 64 seconds.

>  There may well be a problem with the client's ntpd config
>  or the clients network setup ; the interesting thing is that
>  standard ntpd software with a 'normal config', running on
>  of-the-shelf hardware, can show the undesired behaviour.

    That is very strange.


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