[ntp:questions] Re: peer trouble ? reach going down

David L. Mills mills at udel.edu
Thu Aug 7 19:57:55 UTC 2003


Cyril,

This is a feature and very likely no packets are being lost. Consider 
the case when two peers are sending to each other at the same nominal 
poll interval, but where each poll interval is randomized over a 
relatively small range to avoid bunching. It may well happen that one 
peer will not see a message over its own interval if the other peer 
happens to choose a slightly longer interval. In other words, a peer can 
get none, one or two messages during a single poll interval, and this is 
a normal situation.

Dave

Cyril wrote:
> Hi,
> 
> I have 4 NTPs servers in a two city WAN, I would like to do some
> 'peering' between them to add more strength.
> 
> my ntp.conf file look like that for peer1 :
> peer peer2 maxpoll 7
> peer peer3 maxpoll 7
> peer peer4 maxpoll 7
> 
> server server1
> ...
> 
> my ntp.conf file look like that for peer2 :
> peer peer1 maxpoll 7
> peer peer3 maxpoll 7
> peer peer4 maxpoll 7
> 
> server server10
> ...
> 
> Everything work well, but the 'reach' for the peer associations never
> stay a 377.
> I snoop NTP communication I find some strange delay.
> When a peer ask a server, the answer is very fast :
>    fwdrp-dev -> chrivh40.cch.com NTP  client (Wed Aug  6 19:53:47
> 2003)
> chrivh40.cch.com -> fwdrp-dev    NTP  server (Wed Aug  6 19:53:47
> 2003)
>    fwdrp-dev -> SUE.CC.UREGINA.CA NTP  client (Wed Aug  6 19:53:58
> 2003)
> SUE.CC.UREGINA.CA -> fwdrp-dev    NTP  server (Wed Aug  6 19:53:58
> 2003)
> 
> but message between peer are not the same :
>        fwdrp -> gestor01     NTP  symmetric active (Wed Aug  6
> 19:45:08 2003)
>     gestor01 -> fwdrp        NTP  symmetric passive (Wed Aug  6
> 19:46:07 2003)
>     gestor01 -> fwdrp        NTP  symmetric passive (Wed Aug  6
> 19:47:15 2003)
>        fwdrp -> gestor01     NTP  symmetric active (Wed Aug  6
> 19:47:16 2003)
>     gestor01 -> fwdrp        NTP  symmetric passive (Wed Aug  6
> 19:48:23 2003)
>        fwdrp -> gestor01     NTP  symmetric active (Wed Aug  6
> 19:49:24 2003)
>     gestor01 -> fwdrp        NTP  symmetric passive (Wed Aug  6
> 19:50:31 2003)
>        fwdrp -> gestor01     NTP  symmetric active (Wed Aug  6
> 19:51:32 2003)
>     gestor01 -> fwdrp        NTP  symmetric passive (Wed Aug  6
> 19:52:39 2003)
>        fwdrp -> gestor01     NTP  symmetric active (Wed Aug  6
> 19:53:40 2003)
>     gestor01 -> fwdrp        NTP  symmetric passive (Wed Aug  6
> 19:54:47 2003)
> 30s to 2 mn between messages.
> 
> with ntpq peer, I see the reach for all my peer at 376 or 367 or 267,
> but all my
> 'public' internet servers get 377 for reach.
> 
> Can you explain to me why peer exchange are slow ? (and sometime
> one-way,
> because they are not the same stratum 2/3 ?)  and my reach not 377 ?
> 
> We use xntpd 3.5.93e from solaris8. I try the last ntp4 but that
> change nothing.
> 
> Thanks.
> 
> Cyril




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