Time Protocol; Sntp Protocols; Choosing A Protocol - AMX I!-TIMEMANAGER Instruction Manual

Time Protocols

Time Protocol

The Time protocol, based on RFC868, is a very simple straightforward time protocol providing the
number of seconds that have transpired since January 1, 1900 UTC. The current Date and time can
easily be calculated form this value. However, the number of seconds in this protocol is provides as
a 32 bit unsigned number, which can represent a maximum value of 4294967295 (2 ^ 32).
4294967295 seconds from January 1st, 1900 occurs on Feb 7, 2036 at 6h 28m 16s. Therefore, this
protocol can only accurately represent time before this date. Many of the NIST servers, as well and
many Unix, Linux and Windows programs, can provide this time protocol, and it can be reliably
used up until Feb 7, 2036.

SNTP Protocols

The last two Time protocols share the same message format but differ in their connection scheme.
SNTP stands for Simple Network Time Protocol, a subset of NTP or Network Time Protocol, is
based on RFC2030. It is a highly accurate measure of time and date and also measures Date and
Time as the number of seconds from January 1st 1900. However, the number of seconds is provided
in two parts: the number of whole seconds, with a range of 4294967295 (2^32) and fractions of a
second also with a range of 4294967295 (2^32). The Netlinx Master is not able to take advantage of
the fractions of a second offered by SNTP and therefore has the same accuracy as the Time protocol
but SNTP also provides information about the integrity of the data supplied. This makes the SNTP
protocol more accurate than the Time protocol. RFC2030, which defines the SNTP protocol, has
also made a provision for Dates and Time after Feb 7, 2036. SNTP message can represent a Date
and Time accurately until some time in the year 2104. Most of the NIST servers also provide Date
and Time information in SNTP format.
The difference between SNTP (123/udp), SNTP Broadcast (123/udp) is simply one of connection.
It is possible to configure an SNTP server to broadcast the time in SNTP format to an entire
network or node of a network. i!-TimeManager can be configured to actively retrieve the time in
SNTP format from an SNTP server (protocol number 3) or simply listen for SNTP broadcasts on
the network (protocol number 4). Although SNTP broadcasting may sound like an ideal solution
for Date and Time information, the Network Administrator should make this decision.

Choosing a Protocol

So why did we implement so many time protocols? Which Timeserver protocol should you use?
This depends on your Network configuration and your Network administrator. It is probable that
your network already provides some form of Date and Time information, and that information is
probably obtained from a highly accurate source. Most installations of i!-TimeManager should
make use of the time server protocols already available on your network. To find out if such
services are available on your network, contact you Network Administrator.
You might also like to look at commercially available software for Time synchronization.
i!-TimeManager has been tested with Tardis 2000 (http://www.kaska.demon.co.uk) which can
provide all versions of the Time protocols above, including SNTP broadcasting. If you are
interested in synchronizing many computers as well as i!-TimeManager, Tardis 2000 provides a
great solution.
For simple Date Time synchronization, select DayTime (value=1) and leave the server field blank.
A default NIST server will be selected. Most NIST servers supply all three formats of Date and
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