Time Services by CSTV

CSTV puts at everybody disposal on the Internet network the following time services, synchronized directly with the source of the italian standard time: the right time and the NTP primary server .
To be kept updated about these services, one can subscribe to the mailing list time sending a mail to the address time-request@cstv.to.cnr.it with the word subscribe in the field Subject.
To have more information send a mail to timekeeper@cstv.to.cnr.it .

Right time

It is a www page containing the date and the hour at the time of page transmission.

The page reception has variable delays generally greater that 1 second, mainly produced by the transmission performance of the Internet network through all the way from the right time server to the requesting computer.

After the first reading, the page can be manually updated using the reload command available in every www browser.
Pay attention to the cache option of www browsers: it can give rise to readings of old pages of right time. In doubt, give at least one reload command.

The figure shows an example of right time page with an explanation of the less evident elements.

NTP primary server

Since 1993 February, a NTP primary server synchronized by a direct link to the italian standard time of the National Electrotecnical Institute "G. Ferraris" is active at CSTV. The server and the time source are in the same building.

The following table shows the characteristics of the NTP primary.

Internet address tempo.cstv.to.cnr.it (1)
NTP software xntp 3.4o modified (2)
reference clock IEN CTD directly connected
maximum deviation from reference 10 ms
working cycle continuous
access policy open to everybody (3)
geographical position 45°00'54"N, 7°38'20.7"E, 306.6H
site, locality CSTV, Torino - Italy
  1. Avoid numerical server reference, because the numerical address changes more easily than the symbolic address. At this moment, when using the xntp software, the numerical server reference is more convenient, because the xntp name resolution is not yet reliable.
  2. The NTP software was modified at CSTV to allow the usage of the CTD time signal as reference clock. The most recent version (xntp 3.5a) have the modification built-in.
  3. To be kept updated about these services, one can subscribe to the mailing list time sending a mail to the address time-request@cstv.to.cnr.it with the word subscribe in the field Subject.
how to synchronize
Almost every type of computer can be synchronized: PC, MAC and UNIX workstations. The main steps are the following.

To have more detailed information about working principles, installation and usage of NTP software, read the Network Time Protocol (NTP) page.

who is already synchronized
List of computers (NTP clients) already synchronized on the primary server, updated at every midnight. The list includes al NTP clients that synchronized at least one time since the last reset of the NTP software on the primary server.

accuracy of synchronization
The accuracy of the synchronization was measured as the dispersion and the offset from the primary server. The values range from minimums of few milliseconds for computers on the same local network of the server, to maximums of hundreds of milliseconds for computers connected to remote networks.
The following table shows the accuracy values measured on 1996 January on some computers continuously synchronized to the primary server. The hop distance shows the number of Internet nodes (typically routers) between client and sever. The table is ordered by ascending number of hops. All times are in milliseconds.

client site hop distance time distance offset dispersion
same LAN 1 5 2 5
Bologna 5 50 10 30
Torino 6 50 10 70
Pisa 7 140 3 10
Roma 7 140 7 20
Trieste 8 50 4 60
Milano 11 100 5 40

F. Pollastri - The Time of Internet