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NTP [Network Time Protocol]

Unit 4, 2-8 South St

Rydalmere, NSW 2116

T: 13 14 91

F: 1800 659 025

W: www.simplextime.com.au

NTP definition & Application

Document: NTP.doc Issued: October 2008

Q: What is Clock Strata?

NTP is organised in a hierarchical client-server model. In the top of this hierarchy there are a

small number of machines known as reference clocks. A reference clock is known as stratum

0 and is typically a cesium clock or a Global Positioning System (GPS) that receives time

from satellites. Attached to these machines there are the so-called stratum 1 servers (that is,

stratum 0 clients), which are the top level time servers available to the Internet, that is, they

are the best NTP servers available.

Note: in the NTP lingo measure for synchronisation distance is termed as stratum: the number

of layers that an NTP device is removed from a primary time source.

Following this hierarchy, the next level in the structure are the stratum 2 servers which in turn

are the clients for stratum 1 servers. The lowest level of the hierarchy is made up by stratum

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