Model: MTS200 (1U)
Doc. Ref. no. : m08/om/201
Issue no. : 03
User’s Manual
Page 116 of 195
Page 116 of 195
11.3 Timing Output
– NTP
11.3.1 NTP Introduction:
NTP (Network time protocol) is a common method for synchronization of hardware clocks in local and
global Ethernet networks. The software package NTP is an implementation of the actual version 3, based
on the specification RFC-1305. NTP protocol is used to synchronize and maintain the time among
distributed networks of servers and clients. NTP protocol is evolved from Time protocol but is designed to
maintain accuracy and robustness even on the networks involving multiple gateways, high network path
delays and unreliable nets. NTP protocol is applied on the application layer on UDP based IP layer.
The purpose of NTP is to convey timekeeping information (in terms of UTC) from NTP servers to other
time clients via the Internet and also to cross-check clocks and mitigate errors due to equipment or
propagation failures. In NTP basic model, NTP client device sends the NTP packet message over wire to
NTP server (time source) at prefixed/defined interval (as per NTP standard). The NTP server
interchanges IP addresses and ports, overwrites certain fields in the message, inserts current timestamp
in packet, recalculates the checksum and returns the message immediately to NTP client. Information
included in the NTP message allows the client to determine the server time with respect to local time and
adjust the local clock accordingly. After NTP message is received, NTP client calculates time offset, own
local clock frequencies and update in its database at regular intervals to maintain the clock time
synchronization with NTP server time. This may result in either a step-change or a gradual phase
adjustm
ent in time of the NTP client‟s local clock to reduce the offset to zero or as minimum as possible.
The accuracies achievable by NTP client depend strongly on the precision of the local-clock frequency
and stringent control of device and process latencies.
NTP architecture model consists of number of primary reference sources, synchronized by wire or radio
clock. There are other several multiple secondary time sources/clients which are arranged in hierarchal
manner in network which request time from primary reference sources. Under normal circumstances it is
intended that the synchronization subnet of primary and secondary servers assumes a hierarchical-
master-slave configuration with the primary servers at the root and secondary servers of decreasing
accuracy at successive levels toward the leaves.
11.3.2 NTP Output:
mas
TER
T-Sync
Model MTS200 device is equipped with 10/100 Mbps based Ethernet output port which
provides the functionality of NTP server. This NTP output is capable to synchronize time of various NTP
clients such as windows PC, Unix/Linux machines and other clients which support NTP protocol. This unit
operates at stratum 1 level which is the highest level (in terms of accuracy) after atomic clock providing
the NTP timestamp output resolution in milliseconds. Stratum level 1 indicates that a device synchronizes
its own clock from radio clock or satellite clock.
mas
TER
T-Sync
Model MTS200 NTP output operates in
Unicast mode in which NTP server responds only when there is NTP request from NTP clients. MTS200
is also capable to operate in ntp broadcast as well as multicast mode in which MTS200 will send ntp
server frame at configured interval in seconds. NTP clients operating at stratum level lower than 1 (i.e. 2
to 15) can synchronize their time from
mas
TER
T-Sync
Model MTS200 NTP output.
MTS200 continuous to provide NTP output even under Unlock conditions (when there is no satellite
signal available) depending on its internal RTC clock time and accuracy. If required, user can configure
stratum level (2 to 15) of NTP output only for holdover conditions which is applicable when device is in
Unlock condition. This feature provides the indication to NTP client devices whenever device enters
holdover mode during ideal run conditions. Under Lock conditions, MTS200 NTP output will always
operate at stratum level 1 which cannot be changed.
User should change the stratum level of device carefully, after having knowledge of its NTP Server-Client
network hierarchical level architecture. Stratum level decreases by 1 at every NTP server-client level
stages with respect to GPS Clock device stratum level.(Stratum at the topmost level (primary GPS
servers) is assigned as one and each level downwards (secondary servers) in the hierarchy assigned as
one greater than the preceding level). If the stratum level of device is configured at 15 under Unlock
