Association Modes - HPE FlexFabric 5700 Series Network Management And Monitoring Configuration Manual

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
Client/server
Symmetric
active/passive
Broadcast
Working process
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.
On the symmetric active peer,
specify the IP address of the
symmetric passive peer.
A symmetric active peer
periodically sends clock
synchronization messages to a
symmetric passive peer. The
symmetric passive peer
automatically operates in
symmetric passive mode and
sends a reply.
If the symmetric active peer 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 server periodically sends clock
synchronization messages to the
broadcast address
255.255.255.255. Clients listen
to the broadcast messages from
the servers to synchronize to the
server according to the
broadcast messages.
When a client receives the first
Principle
A client can be
synchronized to a
server, but a server
cannot be synchronized
to a client.
A symmetric active peer
and a symmetric
passive peer can be
synchronized to each
other. If both of them are
synchronized, the peer
with a higher stratum is
synchronized to the
peer with a lower
stratum.
A broadcast client can
be synchronized to a
broadcast server, but a
broadcast server cannot
be synchronized to a
broadcast client.
9
Application scenario
As Figure 6 shows, this
mode is intended for
configurations where
devices of a higher
stratum are synchronized
to devices with a lower
stratum.
As Figure 6 shows, this
mode is most often used
between two or more
servers with the same
stratum to operate as a
backup for one another. If
a server fails to
communicate with all the
servers of a higher
stratum, the server can be
synchronized to the
servers of the same
stratum.
A broadcast server sends
clock synchronization
messages to synchronize
clients in the same
subnet. As Figure 6
shows, broadcast mode is
intended for
configurations involving
one or a few servers and a
potentially large client