Unix administration - Help with xntp config ( xntpd on AIX 5.1 and 5.2 )

Author

Help with xntp config ( xntpd on AIX 5.1 and 5.2 )

Chris Allen

2004-05-22, 10:27 pm

I'm trying to setup an ntp hierarchy and I'm getting more and more
confused by the stratum, server, peer, fudge, and prefer settings in
the /etc/ntp.conf file.

Here's my situation and what I'm trying to accomplish:

We have 4 very distinct environments (DEV, TEST, QA, and PROD) each
with between 3 and 10 AIX 5L images.

I would like one server in the PROD environment to be the one system
that syncs its time with clocks outside of our company. Would this
system be considered a stratum 1 system? Also, the other systems in
the PROD environment would sync to this.

I would also like one server in the other 3 environments to sync to
the "company time master" from above. Also, the other systems in the
same environment(Test, Dev, or QA) would sync to these 3 systems.
Would these 3 systems be stratum 2?

Thus, would all my other systems be stratum 3 (including those in the
PROD environment that I would sync to the stratum 1 system mentioned
above)?

Totals: stratum 1=1 stratum 2=3 stratum 3=everything else

Or, would I be better off spreading out the stratum priorities to say
1, 3, & 5?

My confusion stems from the various posts I've read and the lack of
information available about how to setup ntp.conf in the AIX man
pages.

Clarification of how I would use the server, peer and fudge keywords
would be very helpful.

Any assistance is appreciated and it will certainly help clarify how
to setup the 3 very distinct configuration files for my topology.

Regards,

Chris Allen

those who know me have no need of my name

2004-05-22, 10:27 pm

in comp.unix.admin i read:

>I'm trying to setup an ntp hierarchy and I'm getting more and more
>confused by the stratum, server, peer, fudge, and prefer settings in
>the /etc/ntp.conf file.

really? did you search using google groups before posting? there's plenty
of documentation on what each of those things does, when it's useful, &c.
there's an entire newsgroup devoted to ntp: comp.protocol.ntp -- which i'll
grant sounds like it's all about the protocol, but is also used to discuss
ntp in general, including configuration and conceptual issues.

there is a faq as well -- which points to a document which discusses
setting up a local ntp hierarchy -- i hope you've looked at it.

>We have 4 very distinct environments (DEV, TEST, QA, and PROD) each
>with between 3 and 10 AIX 5L images.
>
>I would like one server in the PROD environment to be the one system
>that syncs its time with clocks outside of our company. Would this
>system be considered a stratum 1 system?

no.

>Also, the other systems in the PROD environment would sync to this.

what happens if that one server is down?

>I would also like one server in the other 3 environments to sync to
>the "company time master" from above. Also, the other systems in the
>same environment(Test, Dev, or QA) would sync to these 3 systems.

sounds like your whole company's would be unsync'd when that one server is
down. often that's acceptable, good hardware won't drift too much over
some days waiting for the main time server to return to service.

>Would these 3 systems be stratum 2?
>
>Thus, would all my other systems be stratum 3 (including those in the
>PROD environment that I would sync to the stratum 1 system mentioned
>above)?

no and no.

your main time server would only be stratum 1 if it were receiving a tick
from a trusted clock source (e.g., a gps clock or such). since it'll be
receiving time from an external ntp server it will be at most stratum 2 if
you sync to a stratum 1, which you don't really have enough systems to
warrant, so more likely your main time server would be at stratum 3.

unless you are in a penis size contest the stratum at which you sync is
typically not a source of concern.

>Or, would I be better off spreading out the stratum priorities to say
>1, 3, & 5?

stratums are not priorities, per se.

>My confusion stems from the various posts I've read and the lack of
>information available about how to setup ntp.conf in the AIX man
>pages.
>
>Clarification of how I would use the server, peer and fudge keywords
>would be very helpful.

servers provide time to clients. peers share time with each other.
fudging is used when a config entry's default behavior isn't quite
what is needed.

--
a signature

Doug Freyburger

2004-05-22, 10:27 pm

Chris Allen wrote:
>
> I would like one server in the PROD environment to be the one system
> that syncs its time with clocks outside of our company. Would this
> system be considered a stratum 1 system?

No. A stratum 1 server is a server that is directly connected to
an atomic clock or similarly accurate independent time source. If
you connect over the Internet, your machine will have a stratum
number N+1 compared to whoever you sync with.

> I'm trying to setup an ntp hierarchy and I'm getting more and more
> confused by the stratum, server, peer, fudge, and prefer settings in
> the /etc/ntp.conf file.

Stratum - Number of server hops away from an atomic clock.

Server - Accept time from that machine but do not offer time to it.

Peer - Accept time from that machine and also supply time to it.

Client - The machine specified gets time, but always ignore any
time it gives.

Fudge - Known amount of error in your hardware clock, very much
voodoo and black magic to many folks.

Prefer - Is this which server to give preference, or which protocol
version to give preference?

Juha Laiho

2004-05-22, 10:27 pm

go_uc_bearcats@hotmail.com (Chris Allen) said:
>We have 4 very distinct environments (DEV, TEST, QA, and PROD) each
>with between 3 and 10 AIX 5L images.

How distinct, i.e. do you have firewalls blocking traffic between these
environments?

>I would like one server in the PROD environment to be the one system
>that syncs its time with clocks outside of our company.
....
>I would also like one server in the other 3 environments to sync to
>the "company time master" from above. Also, the other systems in the
>same environment(Test, Dev, or QA) would sync to these 3 systems.

Stratum was already explained in other responses, I don't repeat it here.

I'd consider it better design to have two machines synchronising from
outside servers, and peering with each other. Then, for all the other
machines, set both of these two machines as servers. Two servers to
protect against loss of one.

Also, for the two servers, configure a local clock at some low-priority
(i.e. high-number) stratum, like 6 or 7. This is so that even if you
lose your external time source, at least your network keeps consistent
time. Without this, losing the external time sources would drop the
servers to stratum 9, which means "don't use this time source", and
each machine would continue using solely its local clock.

So, just two different configurations, and not much of a topology,
if you can allow this traffic across your environments.
--
Wolf a.k.a. Juha Laiho Espoo, Finland
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"...cancel my subscription to the resurrection!" (Jim Morrison)

Chris Allen

2004-05-24, 4:32 pm

Thanks for the posts, they have been very helpful. I was not aware
that there was a newsgroup devoted to the discussion of ntp. I will
search there and read the ntp FAQs. I reviewed the information I
found elsewhere within Google but not within the protocol.ntp group
and felt I was missing some key concepts.

Thanks,

Chris Allen