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-   -   APC Network Management Cards Network Time Protocol Support NOT! (http://www.velocityreviews.com/forums/t30259-apc-network-management-cards-network-time-protocol-support-not.html)

Ed M 11-17-2003 03:50 PM

APC Network Management Cards Network Time Protocol Support NOT!
 
This is a little off the topic of Cisco equipment but I'm sure a lot of
people on this newsgroup use APC equipment in their networks.
We have several APC AP9617 Network Management Cards in UPS's and external
enclosures for doing UPS and environmental monitoring.
You can configure these cards to sync their time to an NTP time source (I
have ours syncing to the nearest Cisco router) but there is one glaring
problem: the firmware doesn't support automatic daylight savings time
changes. This means that although the time is within milliseconds of being
accurate it could be an hour out unless you go into each card twice a year
and change the time zone. This is done by setting the time zone forward or
back. For instance if you are physically located in "Eastern Time" you have
to move the card's time zone to "Atlantic Time-Canada" for half the year.

I've discussed this with several people from APC at trade shows and on the
phone and they agreed that this is a surprising omission that should be
fixed but I just got the definitive word back from APC that there are no
plans to support automatic Daylight Savings time in their network cards now
or in the future.

Am I missing something? How hard is building this into a device that is
already syncing to an NTP server?



Walter Roberson 11-17-2003 05:39 PM

Re: APC Network Management Cards Network Time Protocol Support NOT!
 
In article <g76ub.12192$li6.2247@news01.roc.ny>,
Ed M <LEAVESPAMMERSemaendel@frontiernet.net> wrote:
:This is a little off the topic of Cisco equipment but I'm sure a lot of
:people on this newsgroup use APC equipment in their networks.
:We have several APC AP9617 Network Management Cards in UPS's and external
:enclosures for doing UPS and environmental monitoring.
:You can configure these cards to sync their time to an NTP time source (I
:have ours syncing to the nearest Cisco router) but there is one glaring
:problem: the firmware doesn't support automatic daylight savings time
:changes. This means that although the time is within milliseconds of being
:accurate it could be an hour out unless you go into each card twice a year
:and change the time zone.

Why not run in UTC ?
--
This signature intentionally left... Oh, darn!

Andre Beck 11-19-2003 07:57 PM

Re: APC Network Management Cards Network Time Protocol Support NOT!
 
"Ed M" <LEAVESPAMMERSemaendel@frontiernet.net> writes:
>
> This is a little off the topic of Cisco equipment but I'm sure a lot of
> people on this newsgroup use APC equipment in their networks.
> We have several APC AP9617 Network Management Cards in UPS's and external
> enclosures for doing UPS and environmental monitoring.
> You can configure these cards to sync their time to an NTP time source (I
> have ours syncing to the nearest Cisco router) but there is one glaring
> problem: the firmware doesn't support automatic daylight savings time
> changes.


I don't know these cards (I only know other vendor's SNMP adapters to
UPSs), but why should they need localtime in the first place? I actually
consider running core network/IT equipment in anything else but UTC a
bad idea, this easily extends to a UPS. If there is a location where
UTC should be converted to localtime, this is the management side that
monitors the adapter and produces logs, charts, a GUI or such. And this
software will be a lot less complicated and error prone if the time the
adapter itself runs at is UTC (double conversions are evil).

> This means that although the time is within milliseconds of being
> accurate it could be an hour out unless you go into each card twice a year
> and change the time zone. This is done by setting the time zone forward or
> back. For instance if you are physically located in "Eastern Time" you have
> to move the card's time zone to "Atlantic Time-Canada" for half the year.


The card *has* a time zone configuration, but doesn't apply DST? This
is indeed damn silly. I know hardware that just lets you configure a
numeric "timezone" (like +0100 or -0800 or such), in which case manual
DST is obvious. But if they have named timezones, they should implement
them correct - this includes DST.

> I've discussed this with several people from APC at trade shows and on the
> phone and they agreed that this is a surprising omission that should be
> fixed but I just got the definitive word back from APC that there are no
> plans to support automatic Daylight Savings time in their network cards now
> or in the future.


So just run them in UTC. That's probably a bit harder for the US than it
is over here in Europe, but even here, nobody actually has UTC - so we
all have to live with an offset. But believe me, as soon as your network
spans more than one time zone, things become a hell of a lot simpler when
you are just running everything in UTC that is not surfacing to users. If
the US military learned that, anyone can ;)

> Am I missing something? How hard is building this into a device that is
> already syncing to an NTP server?


It *is* damn hard. Interfacing to NTP is trivial (at least in client
style SNTP setups, doing NTP *properly* is rather more sophisticated),
but NTP just speaks UTC. To convert UTC to localtime, a complete
implementation requires time zone descriptions of all existing time
zones of the world, including updates of these descriptions as soon
as something changes. In Europe, Win95 got the DST change wrong in the
late 90s due to an out-of-date timezone description. It's even more
dangerous if you just have a ROM with no actual need for upgrade. The
complete compiled binary "zic" database is 5 MiB on my Linux box,
this is not something you really want in your appliance IMO (even if
it is somewhat redundant and might also fit into <2MiB).

IOS has a nice solution: It allows you to configure rules for just
the time zone you need. They are less complete and especially have
no way to deal with historic or future rule changes, but it allows
you to live with local time for some years without disruption. Then
again, you can just forget all that stuff and live without any dis-
ruption (as long as they don't change UTC itself) when just simply
running UTC. The only somewhat unexpected thing to happen there are
leap seconds, but NTP should deal with them sufficiently.

--
The _S_anta _C_laus _O_peration
or "how to turn a complete illusion into a neverending money source"

-> Andre "ABPSoft" Beck +++ ABP-RIPE +++ Dresden, Germany, Spacetime <-


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