Time Service Accuracy

Hi,

We have a large domain that is having a few domain time issues. All clients
are well connected with fast links.

We have an empty AD forest root domain with a client domain within it. All
pc's and servers are part of the client domain. There are 2 DC's in the root
domain and 4 in the client. There are approx 6000 client pc's/servers in the
domain.

The PDC emulator in the root domain is set to sync with an internet time
source and is always acurate. All other DC's are default setup and
configured to use NT5DS. So are clients.

Throughout the day the time seems to vary quite wildly on the DC's and thus
the clients. Time moves about 15-25 seconds around the real time both
forwards and backwards.

I assumed all clients would just be in time and not move around like this.

Here's an output from w32tm /monitor

(I've had to sanitise it somewhat to remove names and ip's)

RootDC01 [x.x.x.x]:
ICMP: 1ms delay.
NTP: +17.6084182s offset from local clock
RefID: ntp2.usno.navy.mil [192.5.41.209]
RootDC02 [x.x.x.x]:
ICMP: 1ms delay.
NTP: +17.3434951s offset from local clock
RefID: RootDC01 [x.x.x.x]
clientDC01 [x.x.x.x]:
ICMP: 0ms delay.
NTP: +0.2512280s offset from local clock
RefID: RootDC02 [x.x.x.x]
clientDC02 [x.x.x.x]:
ICMP: 0ms delay.
NTP: +17.1781377s offset from local clock
RefID: RootDC02 [x.x.x.x]
clientDC03 [x.x.x.x]:
ICMP: 1ms delay.
NTP: +27.6088924s offset from local clock
RefID: RootDC02 [x.x.x.x]
clientDC04 [10.221.24.26]:
ICMP: 1ms delay.
NTP: +17.7371546s offset from local clock
RefID: RootDC02 [x.x.x.x]

At other times I can check these and everything is within 1 tenth of a second.

Any Ideas?