|
Public NTP Time Servers |
From
NBS Special Publication 432 (out of print) These pages contain lists of Network Time Protocol (NTP) public time servers. They are provided for information purposes only and represent the best information available at the current date. The operators of the servers listed do not commit to provide time service other than on a volunteer basis and with no guarantee of accuracy or availability. Further information of a technical nature can be obtained from the ntp@ni.umd.edu list. To subscribe to this list, contact mailto:ntp-request@transsys.com. Alternatively, if possible, please subscribe to the newsgroup comp.protocols.time.ntp which is gatewayed to the mailing list. Please send corrections or additions to mailto:mills@udel.edu in HTML format as used in the list pages. If an error is found by other than the responsible person, please first request that person to submit the correction.
As the load on the hosts supporting NTP primary (stratum 1) time service is heavy and always increasing, clients should avoid using the primary servers whenever possible. In most cases the accuracy of the NTP secondary (stratum 2) servers is only slightly degraded relative to the primary servers and, as a group, the secondary servers may be just as reliable. As a general rule, a secondary server should use a primary server only under the following conditions:
In order to ensure reliability, clients should spread their use over many different servers. As a general rule, no more than two clients per network should use the same server on another network; however, in order to simplify management of host configuration tables, many hosts on the same network may use the same (redundant) servers on the same network.
Unix users are strongly encouraged to adopt the latest NTP version software in the compressed tar distribution shown in the NTP home page. Besides providing more accurate, reliable service, the latest version automatically increases the polling intervals for all peer associations, but without sacrificing performance. This can significantly reduce network loads, as well as the loads on the busy primary servers, some of which have over 700 clients.
The list of primary (stratum 1) and secondary (stratum 2) designates the NTP time servers available for public access under stated restrictions. Each entry gives the country code, state (US only), host name, Internet address, approximate location and geographic coordinates (if available), synchronization source (stratum, type of radio or satellite receiver and host type), suggested service area, access policy (as notified) and responsible person name and e-mail address. Most servers indicate the NTP version as well. It is always wise to consult the DNS to verify host addresses, which are changed from time to time. When more than one address is given, preference should given to each in order.
Please respect the access policy as stated by the responsible person. It is very important that potential clients avoid use of servers not listed as open access, unless approved first by the responsible person. This especially includes indiscriminate use of servers not listed in the list, since this can be disruptive. The responsible person should always be notified upon establishment of regular operations with servers listed as open access. Servers listed as closed access should NOT be used without prior permission, since this may disrupt ongoing activities in which these servers are involved.
All primary and secondary servers listed have no access restrictions, so that service is available for any client with a valid IP address. Where noted, some servers enforce a limit on the number of clients from any one network other than the server network itself. Where noted, some servers provide a cryptographic authentication service. Contact the site operators for further details.