Time Service is more complicated than just having a single NTP server. But it can be useful and is not really a luxury.
Two primary reasons for local time service are to reliably serve a network that is relatively or completely isolated from the general internet, and, to provide a local time source for "dumb" clients that is closer (less jitter) in network terms. Other reasons can include policy (everything in the network uses the same identical time service), policy (the time service is locally controlled), operational simplicity (the routers don't need to run NTP), and, separation of functions/operational responsibility (your run your servers, they run the backbone, I tell you the time. Implementing a local time service is actually fairly simple, but fewer than four servers is wasted effort. I can't explain in just a few words how the servers interact and compute delays and jitter to come to an "accurate" time. Take my word or ask David Mills for all that. Implementation of an internet-referenced time service involves the following: 1. Select a set of stratum one servers - pick open access servers or get permission to use limited access servers. Four to six should do. 2. Select a set local hosts on your network - DNS servers, for example. These should be well distributed. Four to six should do. The actual NTP load is small compared to DNS queries. 3. Configure the local hosts as peers using the stratum one set as servers. Use crypto authentication if you feel the need. 4. Add NTP monitoring to your network management process. 5. Advertise the local time servers to your network - DHCP, word of mouth, configuration requirements, configuration scripts, standard builds, etc. It is simple enough to do for a five node home network. It is almost that simple for a network with hundreds of thousands of client nodes. I've done both. On Oct 24, 2010, at 12:29 PM, Brandon Kim wrote: > > I guess what I'm trying to understand is, is having your own NTP server just > a luxury? > > I personally would like to have my own, I just need to pitch its advantages > to my company. Unless everyone here on the NANOG group > clearly spells it out to me that it's a luxury. > > I can see it as an added service/benefit though to our customers..... > > > >> Date: Sun, 24 Oct 2010 17:55:22 +0200 >> From: eu...@leitl.org >> To: nanog@nanog.org >> Subject: Re: NTP Server >> >> On Mon, Oct 25, 2010 at 02:51:24AM +1100, Ben McGinnes wrote: >> >>>> How do you knew that your local NTP server knew what time it is? (for >>>> sure) >>> >>> By polling as many stratum 1 and 2 time servers as possible. Having >>> your own stratum 2 server(s) beats nebulous NTP servers out in the big >>> bad Internet every time. >> >> For those you care about that: >> >> http://leapsecond.com/time-nuts.htm >> > = James R. Cutler james.cut...@consultant.com
