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Association modes – H3C Technologies H3C S6300 Series Switches User Manual

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To ensure time accuracy and availability, you can specify multiple NTP servers for a device. The device

selects an optimal NTP server as the clock source based on parameters such as stratum. The clock that
the device selects is called the reference source. For more information about clock selection, see the

related protocols and standards.
If the devices in a network cannot synchronize to an authoritative time source, you can select a device that

has a relatively accurate clock from the network, and use the local clock of the device as the reference
clock to synchronize other devices in the network.

Association modes

NTP supports the following association modes:

Client/server mode

Symmetric active/passive mode

Broadcast mode

Multicast mode

Table 1 NTP association modes

Mode Working process

Principle

Application scenario

Client/server

On the client, specify the IP
address of the NTP server.
A client sends a clock
synchronization message to the

NTP servers. Upon receiving the
message, the servers

automatically operate in server

mode and send a reply.
If the client can be synchronized

to multiple time servers, it selects
an optimal clock and

synchronizes its local clock to the

optimal reference source after
receiving the replies from the

servers.

A client can be
synchronized to a server,

but a server cannot be

synchronized to a client.

As

Figure 6

shows, this

mode is intended for

configurations where

devices of a higher stratum

are synchronized to
devices with a lower

stratum.