20071230

Happy New Year! It's about time...

Time for a New Years Resolution! Establish an NTP server at every site I work on, and point as many devices to it as I can. (I'll do this to save everyone some time.)

Consider taking a look around your installation. How long would it take to check the uptimes of the devices, and also check their on-board Real Time Clocks. How many do you think are correctly showing the current time, within +/- 10 minutes? For your network gear, how many are showing log timestamps as the "from startup" uptime stamp, instead of a date/time notation?

Now, consider that, in the time it would take to EVALUATE your clocks and timestamp settings, that you could probably FIX THEM, not just record the results! If you plan to go and touch all the gear anyway, why not save some time, and SET the clocks, instead of checking them?

But, when was the last time anyone bothered to do this, in your installation? Maybe the clocks on your devices only get set when each device is installed. (If you ship devices between data centers, across timezones, do you make a point of changing the device clocks when you receive them into your installation?) Let's face it, these clocks are cheap, and they ALL have some drift in them. Even if the drift is minimal, the error is cumulative, and can be significant across 3 or more years. You complicate the drift when you don't use a stable starting point. (What time reference does everyone use when they set device clocks? Probably their independent wrist watch?)

In the same way that you need to spend some money to make more money, you need to spend time to make more time! NTP is a great way to set clocks, and keep them close to the current time. (Even a daily time sync will all but eliminate the effect of drift on the cheap clocks.) Most devices have a no-cost client available, and many servers and some network gear have a no-cost NTP Server option available. If you have a complicated network, with multiple customers or DMZs, you can invest in an appliance that uses GPS or the cellular phne service to provide a drop-in connection on an isolated network. You just need to take some time to set up a server, and then set your devices to be clients.

Technically, all of this work (and invested time setting up NTP) doesn't save time, per se. What it will do is reduce the time you spend tracking down problems. Calculating time-math is hard. Correlating time offsets in log files between devices with unsynchronized clocks takes a LOT of time. But, when you have an "event" in your installation, and you need to find the Root Cause, you need to compare a bunch of logs, to figure out what happend first, then second, and etc.

If you take the time to set up an NTP server, you make it quick and easy to 'set and forget' the clocks on new devices coming into your installation. When you take the time to point all of your existing devices to the NTP server, you'll save time comparing the logs on all future 'events'. It's hard to guess how much time, or how soon you will recover that time, but it WILL happen. Just give it time.

-Zonker-

Some NTP appliance resources I've found to be interesting:
VMware NTP appliance VM info
Symmetricom S200
J-Time (Meinberg USA) Lantime M300
Brandywine Communications NTV-100RG

1 comment:

tklimasewski said...

Hello Zonker,
Nice thoughts to start the new year. I have clients who use our GPS-based NTP server appliance to prove the timing of events in the court of law. So in addition to saving time when troubleshooting network issues, network clock synchronization to a legally traceable time source can help with legal disputes that can become extremely costly. If you ever work on a network to support a mission-critical app, I'll be more than happy to show you how we've built reliability, security and accuracy into our NetClock ntp server.
Tim Klimasewski, www.spectracomcorp.com