Hi Sean: By local I meant in-house, on-site in our datacenter. As far as what applications could use our NTP service, I would leave that up to each client and what they are running. For my own personal purposes, it would just be for log purposes. (error logs, syslogs, etc etc)
I have heard that routers don't make good NTP servers since they weren't designed to keep track of time. This, I have read from a Cisco source. Can't remember where though. Or maybe they were just referring to older less powerful routers like 2500 series... Brandon > Date: Sun, 24 Oct 2010 14:42:24 -0400 > From: s...@donelan.com > To: nanog@nanog.org > Subject: Re: NTP Server > > On Sun, 24 Oct 2010, Brandon Kim wrote: > > 1) How necessary do you believe in local NTP servers? Do you really > > need the logs to be perfectly accurate? > > 2) If you do have a local NTP server, is it only for local internal > > use, or do you provide this NTP server to your clients as an added > > service? > > 3) If you do have a local NTP server, do you have a standby local NTP > > server or do you use the internet as your standby server? > > First terminology. What do you mean by a local NTP server? > > Almost any Cisco/Juniper router, Unix server and some recent Windows > servers have NTP server software and can synchronize clocks in your > network. So you may already have a NTP server capable device. You just > need to configure it, and give it a good source of time. It would be a > Stratum 2 or greater NTP server because the good source of time is > another NTP server. Left to itself, NTP is pretty good at keeping clocks > in arbitrary networks synchronized with each other. But most people are > also interested in synchronizing clocks with some official time source. > > The Network Time Protocol doesn't really have the notion of a "standby" > server. It uses multiple time sources together, and works best with about > four time sources. But for many end-systems, the Simple Network Time > Protocol with a single time source may be sufficient. > > If you are in a regulated industry (stock broker, electric utility, 9-1-1 > answering point, etc) there are specific time and frequency standards you > must follow. > > On the other hand, are you are asking about a local clock receiver (radio, > satellite, etc) for a stratum 1 NTP server? Clock receivers are getting > cheaper, the problem is usually the antenna location. > > Or on the third hand, are you asking about local primary reference clock > (caesium, rubium, etc) for a stratum 1 NTP server? These are still > relatively expensive up to extremely expensive. > > Or on the fourth hand, are you a time scientist working to improve > international time standards. If you are one of these folks, you already > know. > > > Most major ISPs use NTP across their router backbone, and incidently > provide it to their customers. The local ISP router connected to your > circuit probably has NTP enabled. > > Required accuracy is in the eye of the beholder. NASDAQ requires brokers > to have their clocks synchronized within 3 seconds of UTC(NIST). 9-1-1 > centers are required to have their clocks synchronized within 0.5 seconds > of UTC. Kerberos/Active Directory requires clocks to be synchronized > within 5 minutes of each other. > > If your log files have a resolution of 1 second, you probably won't see > much benefit of sub-second clock precision or accuracy. If you are > conducting distributed measurements with sub-microsecond resolution, you > probably will want something more. > > >