MILLS@USC-ISID.ARPA (11/13/85)
Folks, In response to questions from several clockwatchers, the following list gives the names of known NTP servers, their addresses and related information. Host Name Address Clock System Contact --------------------------------------------------------------------------- DCN1.ARPA 128.4.0.1 WWVB fuzz mills@usc-isid.arpa DCN5.ARPA 128.4.0.5 DCN fuzz mills@usc-isid.arpa DCN6.ARPA 128.4.0.6 DCN fuzz mills@dcn6.arpa DCN7.ARPA 128.4.0.7 DCN fuzz mills@usc-isid.arpa DCN8.ARPA 128.4.0.8 DCN fuzz mills@usc-isid.arpa DCN9.ARPA 128.4.0.9 none Sun 4.2bsd oconnor@dcn9.arpa FORD1.ARPA 128.5.0.1 GOES fuzz jay@ford1.arpa TRANTOR.UMD.EDU 128.8.0.14 none VAX 4.2bsd louie@trantor.umd.edu GW-UMICH.EDU 128.82.0.1 WWV fuzz hwb@gw-umich.edu The System column indicates the processor and operating system. The "fuzz" are various LSI-11 systems running a protocol-workbench system implemented by me. Mike O'Connor wrote an NTP server for 4.2bsd, which is in test on the hosts indicated. The Clock column above indicates the normal soruce of synchronization information: WWVB NBS Radio WWVB, Boulder, CO. (Spectracom 8170 WWVB Receiver) WWV NBS Radio WWV, Ft. Collins, CO. (Heath GC-1000 Most Accurate Clock) GOES GOES Satellite (True-Time 468DC Satellite Synchronized Clock) DCN DCNet local-net protocols none unknown or unspecified The DCNet hosts 128.4 normally synchronize using DCNet local-net protocols to the WWVB primary clock connected to DCN1.ARPA. If this clock or DCN1.ARPA itself should fail, the first-order backup is the WWV secondary clock connected to DCN6.ARPA, while the second-order backup is via the FORDnet gateway to 128.5. The FORDnet hosts 128.5 normally synchronize using DCNet protocols to the GOES primary clock connected to FORD1.ARPA, with first-order backup via DCNet 128.5 and second-order backup via UMICHnet 128.82. Hosts requesting NTP time should normally use only those hosts with directly connected primary clocks, in this case DCN1.ARPA, FORD1.ARPA and GW.UMICH.EDU. If any of these hosts indicate in an NTP response other than code 1 in the Status field (clock operating normally) or code 1 in the Reference Clock Type Field (primary reference), the primary clock is down or operating incorrectly, and the time indicated may be in gross error. If any of these hosts indicate code 3 in the latter field (secondary reference not using NTP), the primary clock is down but the host has synchronized to another source presumably operating correctly. Depending on the synchronizing source and path, the NTP time indicated by various hosts may have small offsets (in the order of milliseconds) relative to the source. In order to calibrate these offsets, certain special hosts have been instrumented to return time directly from the radio clock. In order to preserve the highest accuracy, the time is available only in ICMP Timestamp messages. Following is a list of these special hosts: Host Name Address Clock ------------------------------------- DCN-WWV.ARPA 128.4.0.14 WWV DCN-WWVB.ARPA 128.4.0.15 WWVB unspecified 128.5.0.19 GOES unspecified 128.82.0.17 WWV These hosts can be used to obtain time from the specified clock regardless of the current synchronizing source used by the directly connected host or state of the clock itself. Dave -------