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.

accuracy
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.

update
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.

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

• H: hours go from 0 to 23
• T: acronym of the time zone, CET for winter time, CEST for summer time
• S: information about the day-light saving time.
• L: information about the leap second insertion.

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.

characteristics
The following table shows the characteristics of the NTP primary.

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.

• The computer to be synchronized must have the reachability of the primary server through Internet.
• If not already present in the operating system of the computer, it needs to install a suitable version of NTP software.
• The NTP software must be configured defining tempo.cstv.to.cnr.it as NTP server.
• The NTP software must be started. The simplified versions synchronize to the server immediately. The complete versions take about ten minutes to synchronize.

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.

F. Pollastri - The Time of Internet