esm module and ntp problem

JP Vossen vossenjp at
Sun Jan 12 13:50:00 CST 2003

On Sun, 12 Jan 2003 fluke at wrote:

> Backups are usually done over TCP and NTP uses UDP.  A side effect of this

Yeah, but the backup job is LOCAL to the machine--no network traffic!

> 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
> auto-negotiated.
> 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... :-(

JP Vossen, CISSP              |:::======|                jp at
My Account, My Opinions       |=========|
"The software said it requires Windows 98 or better, so I installed

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