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PDF NTS-3000 Data sheet ( Hoja de datos )
| Número de pieza | NTS-3000 | |
| Descripción | Network Time Synchronisation USER MANUAL | |
| Fabricantes | ELPROMA | |
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Network Time Synchronisation
USER MANUAL
Time Server NTS
ELPROMA NTS–3000
ELPROMA Electronics
www.elproma.com
March 31, 2003
1
1 page  
ELPROMA Electronics
Network Time Service NTS–3000
2 Hardware
The NTS–3000 timeserver set includes:
• NTP timeserver unit (rack19 mounted 1U)
• GPS antenna with 200m. cable and frequency converter with built-in over
voltage protection
• DCF77 antenna with 20m. cable /optionally/
• RS-232 configuration cable
• Power cable 230V
• CD with software utility and PDF manual
Timeserver unit is a multiprocessor system with 3 not depended (not routed)
fast Ethernet 10/100Mbs interfaces. It is design and manufactured without
ventilators, fens or any other mechanical parts. Metal housing is an important
part of NTS–3000 cooling system but it is designed on a way that NTS–3000
can be located in the neighborhood of any device working inside rack19 mount
frame.
Single serial (9pin D-SUB connector) port is dedicated for setup utility, but
it can be also used to connect DCF77 antenna (option) later on. The 2x20 char
LCD shows GPS communication and timestamp information.
Figure 1: Front panel of NTS–3000. LAN ports
Figure 2: Back panel of NTS–3000
All LAN connectors contains 2 led: yellow indicates cable connection, green
one flashes while data transmission.
On the back panel there is a power connection 230V AC (50Hz) and GPS
antenna rounded connector.
NTS–3000 has 2 independent build-in power supplies: one for powering
server unit and the second one for powering the GPS antenna. The optional
backup DCF77 antenna is powered via RS232 signal lines.
5
5 Page 
ELPROMA Electronics
Network Time Service NTS–3000
7 NTP - Network Time Protocol
Before you learn how to setup NTS–3000, you also should read about what NTP
itself.
NTP is a common method for time synchronization over networks. It is
a protocol but a very special one. The NTP is much different from any of
known other communication protocols. It is because NTP does not base on the
principles of synchronizing machines to each other. It is based on the principles
of having all machines get as close as possible to the UTC time provided by
NTS–3000. How it works?
NTS–3000 forms a statistic of delays and other data necessary to calculate
local client RTC offset. Knowing time difference the adjustment of the own
RTC clock can be preceded individually by each NTP client.
NTP works on a hierarchical model in which a small number of servers gives
time to a large number of clients. The clients on each level, or stratum, are in
turn, potential servers to an even larger number of clients on a higher numbered
stratum. Stratum numbers increase from the primary (stratum 1) servers to
the lowest numbered strata at the bottom of the tree (stratum 15). Clients can
use time information from multiple servers to determine automatically the best
source of time and prevent wrong time sources from corrupting their own time.
For sure it may take several minutes (or even hours) to adjust a system time
to the ultimate degree of accuracy. There are several reasons for this. The most
important one is that NTP averages the results of several time exchanges in
order to reduce the effects of variable latency. This may take several minutes
for NTP to even reach consensus on what the average latency is. Generally it
happens in about 5-10 minutes. In addition, it often takes several adjustments
for NTP to reach a synchronization. The result is that users should not expect
NTP to immediately synchronize two clocks. The ntpdate command can be
used if an instant synchronization is needed.
The peers command can be used in ntpq to determine wheather the synchro-
nization has been achieved. When a client has synchronized, the synchronization
server is listed with an asterisk in front of it.
To allow clocks to quickly achieve the high accuracy, yet avoid overshooting
the time with large time adjustments, NTP uses a system where large adjust-
ments occur quickly and small adjustments occur over time. For small time
differences (less than 128 ms), NTP uses a gradual adjustment. This is called
slewing. For larger (but still less than 17 minutes) time differences, the adjust-
ment is immediate. This is called stepping.
If the accuracy of a clock becomes too insufficient (off by more than about 17
minutes), NTP aborts the NTP daemon, with the assumption that something
has gone wrong with either the client or server. In order to synchronize well
with a server, the client needs to avoid step adjustments.
Due to NTP specification NTS–3000 is visible over network as a peer. Sin-
gle peer can contain more than single timeservers in order of a hierarchy called
stratum. The top of the stratum tree is preserved for radio-controlled time-
servers such as NTS–3000. Therefore NTS–3000 will always be your stratum1
timeserver. Other connected computers can also work in timeserver mode but
they will be set down to stratum2 or even much below.
The NTS–3000 time server supports multiple source of time. Each source
is Stratum 0 (except RTC working on Stratum 1 level). The enterprise of
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet NTS-3000.PDF ] | |
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