While time servers keep networked devices synchronised, they don't recognise daylight saving shifts. To help clear up the issue, we spoke with Paul Skoog, a product marketing manager at Symmetricom, which sells time and frequency products and services, including network time servers.
What are network time servers, what do they do and what is their role in the network?
Time servers are clocks that reside on the network, either on the Internet or inside your firewall, that provide time to servers, workstations, routers, etc. on the LAN. The time provided by a time server is always UTC [Co-ordinated Universal Time], is usually traceable back to a national time source such as the US National Institute of Standards and Technology or Naval Observatory, and supports the Network Time Protocol (NTP).
UTC has no time zone and is related to atomic time and the earth's spin rate. Probably the most popular source of precise UTC time is via the GPS satellite system. With a GPS-referenced network time server on your network, you have a clock that's accurate down to the sub-microsecond level, as well as being reliable and secure.
To actually synchronise the time on your network, you need to configure servers and workstations to get their time from the time server by way of an NTP daemon in the operating system or an NTP time client. This will synchronise the client machine typically to a few milliseconds to UTC internally. Most people don't realise this. It's the user of the operating system that configures the local time zone for that machine. The beauty of UTC and time servers is that they can all be synchronised very closely to one another, independent of time zones, because time zones happen locally on your computer.
Can you update your time server so that it is in compliance with the daylight-saving change for your local network?
No, NTP time servers are time-zone agnostic. They serve only UTC time. Say you put a time client on your computer and configure it to get time from a time server. It can be any time server on the planet, could be one that I sell you, could be one that the government provides out on the Internet. Your time client will synchronise to that time server and it will always be to UTC time. Locally, your operating system, such as a Microsoft OS, keeps track of time according to UTC. But it makes an adjustment when it displays the time or for time stamps, because you told your computer that you are located in a certain time zone. What the operating system now does is get UTC time from the time server and then adjusts it according to your time zone and daylight saving rules. But internally, hidden from you, you're synchronising to the time server using UTC time.
So even though organisations have network time servers, they still have to make these changes in the operating system?
They absolutely have to because the time server is delivering time in UTC format -- always. They may point their primary domain controller, for example, to a time server and it's getting UTC time and then it's making the conversion to what we call local time. That's where this daylight saving change is a big deal for IT folks. Unless the user updates each computer to follow the new daylight saving rules, it will follow the old rules and have the incorrect time for three weeks starting on March 11. Like your article brought out, I can only imagine the headaches this may generate for the unprepared.
So how do these network time servers play into daylight-saving shifts? Do they play into it at all?
No. A network time server is completely time-zone and daylight-saving-time agnostic. It only tracks UTC and serves time in UTC. This is actually a very convenient aspect of the network time protocol. Since all time servers serve UTC time, as users we only need the IP address of the time sever to synchronise to it. The actual location of the time server and what time zone it may be in is irrelevant. We configure the time zone on our computers.
Have you had questions from clients about this?
Certainly. Understanding how we as humans synchronise, distribute and display time is a big deal. Particularly with so many time zones and daylight saving rules implemented by each country around the world. We put up a page that speaks briefly to it for our products. But here's the key thing to understand: Your network time server , whether it's the one on your network that we perhaps sold you or one you synchronise to out there on the Internet, is going to serve UTC. It's completely daylight-saving-time agnostic, and you will have to make daylight saving adjustments on your local machines via the operating system. It's just a fact.
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