Need a Time Server?
If you have contacted us because you need a time server, you can use our server subject to the contraints discussed below. We offer one stratum 1 server for time-setting for servers off-campus, and a tier-2 server for Purdue users. Our stratum 1 server is part of the NTP Pool, and that service may provide a good option if you need more or other time servers, in addition to (or in place of) our servers. Other servers are listed at the time servers site.
We provide two NTP servers for use inside and outside of Purdue University. These consist of a stratum 1 time server (CDMA-based) for any Internet users, and an additional stratum 2 server for internal Purdue users.
The stratum 1 server is currently a EndRun Technologies Tempus LX™ CDMA-based server, which uses cell-phone timing signals as a time standard. The location of the CDMA-based server is such that we have an extremely strong signal.
The stratum 2 server for internal Purdue usage is running on our Cisco 7500 series router.
We make no guarantees about this service. The servers may go down at any time, or become unreachable to users outside Purdue. We will try to maintain reasonable availability, but any service is provided on an "as is" basis as a courtesy. We make no warranties about the accuracy of the time signal beyond our good-faith belief that it is as accurate as can be achieved using our stock hardware and software.
If you wish to use our time servers, we ask that you observe the following:
For users ON THE PURDUE WEST LAFAYETTE CAMPUS only:
We request that you point your NTP requests at horologe.cerias.purdue.edu. This will be the best connection (lowest delay and jitter) for almost all Purdue campus users. It is a stratum 2 server with a direct connection to our stratum 1 time servers and it is present in a clock-net of three servers synced to 8 external Stratum I servers. For on-campus use there should be no discernable difference in time accuracy between this server and the stratum 1 servers. In fact, to get to the stratum 1 servers your packets would need to transit an additional router and switch, so horologe should have less delay and jitter.
Hosts in Computer Science are a special case, and they should reference andromeda.cs.purdue.edu as a time source.
Campus hosts that must reference a Stratum I host should reference andromeda.cs.purdue.edu.
There is no need to inform us or register to use these servers from on campus.
For users NOT AT PURDUE:
Please send email to email@example.com if you intend to use our time server. Let us know which machine/domain will be involved, and an email address if we need to contact you.
Use the DNS name of our server rather than the IP addresses. The IP address may change without warning but the name will remain constant. If we need to change our server for some reason, use of the DNS name instead of the IP address should make any such change transparent.
If you have a slow connection or long round-trip delay to our server, then pick another NTP server or establish your own level 1 server (see below). This will give you better time sync.
Instead of having multiple machines connect to our servers, establish your own stratum 2 or 3 server. Have a single machine connect to our servers to set its time, then have all your local machines use it as their time source. This should work better by reducing the aggregate overall network delay. It also reduces load on our servers!
Please do not overpoll our servers. That is, leave the frequency at which you check to something reasonable -- if your internal clock is so bad as to require a resync every few minutes, then you should get a better machine or your own time server!
Standard NTP suggests that a good onboard clock with appropriate NTP settings will settle into a pattern of polling about once every 1024 seconds (maxpoll = 10).
If you have need of authenticated time (using MD5, as defined in the NTP protocol) then we can exchange key information to enable this. Contact firstname.lastname@example.org. We currently do not have autokeying set up on any of the servers.
Establishing your own server
Our Stratum 1 server comes as a rack-mountable unit with an external antenna. This is generally easy to set up. CDMA units work from cell phone signals, so anywhere inside where there is a good cellphone signal is appropriate.
We recently added the EndRun Tempus LX server. This also was extremely easy to set up and run -- less than 10 minutes from out of the box to locked and serving a signal! The documentation is good, and the interface is simple. We are very pleased with this server, too. EndRun makes servers that provide a time signal from either GPS or CDMA signals; ours is a CDMA unit.
Establishing your own time server might be a good move, especially if you need a secure time source, because you can run it inside your firewall. Cost for a system is generally a few thousand dollars for US customers. Options are available to get more precise local clock crystals for times when the external time source is unavailable, but that adds expense. For more details, you can visit EndRun Technologies.
For More Information
Lots more information on NTP, including the latest software, is available at http://www.ntp.org/.
February 09 2015.