H3C Technologies H3C S7500E Series Switches - Manual (Page 69)

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z Authenticator: authentication information.
Operation Modes of NTP
Devices running NTP can implement clock synchronization in one of the following modes:
z Client/server mode
z Symmetric peers mode
z Broadcast mode
z Multicast mode
You can select operation modes of NTP as needed. In case that the IP address of the NTP
server or peer is unknown and many devices in the network need to be synchronized, you can
adopt the broadcast or multicast mode; while in the client/server and symmetric peers modes, a
device is synchronized from the specified server or peer, and thus clock reliability is enhanced.
Client/server mode
Figure 3-3 Client/server mode
When working in the client/server mode, a client sends a clock synchronization message to
servers, with the Mode field in the message set to 3 (client mode). Upon receiving the message,
the servers automatically work in the server mode and send a reply, with the Mode field in the
messages set to 4 (server mode). Upon receiving the replies from the servers, the client
performs clock filtering and selection, and synchronizes its local clock to that of the optimal
reference source.
In this mode, a client can be synchronized to a server, but not vice versa.