Avaya Configuring IP Utilities Manuel d'utilisateur télécharger pdf (Page 43)

TCP, FTP, Telnet, and NTP Concepts

114071 Rev. A 2-13

NTP Overview

The Network Time Protocol (NTP) synchronizes the timing of internal clocks of

various internet devices across large, diverse networks. NTP runs over UDP,

which in turn runs over IP. The NTP protocol speciﬁcation is documented in RFC

1305.

Each router on the network contains an internal system clock that is used to

maintain accurate time for the router. NTP adjusts each clock’s time to universal

standard time. Because NTP is unaware of the Greenwich mean time (GMT) time

zones, you need to set the time zones using the

date command from the

Technician Interface.

NTP Architecture

The NTP architecture model is based on a hierarchy consisting of an NTP client

and primary and secondary time servers. The NTP client is an internet device that

receives time information from an NTP time server and synchronizes its internal

clock to it. The NTP client does not forward time information to other internet

devices running NTP.

A primary time server is the authoritative time source in the hierarchy, meaning

that it is the one true time source to which the other NTP devices will synchronize

their internal clocks. Located at the root of the hierarchy, the primary time server

is synchronized by a wire or radio clock to universal standard time. Secondary

time servers synchronize with primary time servers or other secondary time

servers to form a synchronization subnet (Figure 2-5.) Secondary time servers are

located at successive levels from the primary time server based on timer accuracy

and stratum level.

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Avaya Configuring IP Utilities Manuel d'utilisateur Page 43