esm module and ntp problem fluke at
Sun Jan 12 14:13:15 CST 2003

Backups are usually done over TCP and NTP uses UDP.  A side effect of this 
is that if you have a mismatch with the ethernet duplex configuration (NIC 
set to full duplex on a half duplex hub, NIC set to half duplex on a full 
duplex switch, etc) then the backups will error correct over the mismatch 
at the cost of performance but NTP communication will not error correct at 
all.  Hence, backups will just take a little longer than they should but 
NTP syncs will stop entirely while the network utilization is 
moderate-heavy.  When network utilization is low the duplex mismatch will 
not cause as many lost packets and NTP will re-sync again.

Some administrators make the mistake that a switch does auto-negotiation 
just because the NIC is able to auto-sense the speed.  Please keep in mind 
that speed auto-detection does not mean that the duplex was 

On Fri, 10 Jan 2003, JP Vossen wrote:

> On Fri, 10 Jan 2003, Michael Redinger wrote:
> > Summary:
> > when esm kernel module is loaded on a 2650, the ntpd regularily looses the
> > synchronization. 100% reproduceable for me.
> I have a PE500SC and am NOT running the esm module, byt my ntp loses
> synchronization every Monday morning just as my backup job is ending.  All RH8
> errata applied.  Search the list archives for details.  No joy so far... :-(
> Later,
> JP
> ------------------------------|:::======|--------------------------------
> JP Vossen, CISSP              |:::======|                jp at
> My Account, My Opinions       |=========|
> ------------------------------|=========|--------------------------------
> "The software said it requires Windows 98 or better, so I installed
> Linux..."
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