Huawei AR150 Series Configuration Manual page 102

Huawei AR150&200&1200&2200&3200 Series Enterprise
Routers
Configuration Guide - Device Management
Figure 5-5 Broadcast mode
Broadcast Server
Multicast Mode
Multicast mode is useful when there are large numbers of clients distributed in a network. This
normally results in large number of NTP packets in the network. In the multicast mode, a single
NTP multicast packet can potentially reach all the clients on the network and reduce the control
traffic on the network.
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Issue 05 (2014-01-16)
P e r i o d i c a l l y b r o a d c a s t c l o c k
synchronization packets (mode5)
I n t e r a c t i o n o f c l o c k
synchronization packets (mode3
and mode4)
P e r i o d i c a l l y b r o a d c a s t c l o c k
synchronization packets (mode5)
Multicast server: A server running in multicast mode sends clock synchronization packets
to a multicast address periodically. The value of the Mode field in a packet is set to 5. This
indicates that the packet is sent by a host that runs in multicast mode. The host running in
multicast mode is usually a clock server running high-speed broadcast media on the
network, which provides synchronization information for all of its peers but does not alter
the clock of its own.
Multicast client: The client listens to the multicast packets from the server. When the client
receives the first broadcast packet, the client and server exchange NTP packets whose
values of Mode fields are 3 (sent by the client) and the NTP packets whose values of Mode
fields are 4 (sent by the server). In this process, the client enables the server/client mode
for a short time to exchange information with the remote server. This allows the client to
obtain the network delay between the client and the server. Then, the client returns the
multicast mode, and continues to sense the incoming multicast packets to synchronize the
local clock.
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Broadcast Client
Initiate a request for server/client mode
after receiving the first broadcast
packet
Obtain a network delay, and enter
broadcast client mode
Receive the broadcast packets, and
synchronize the local clock to that of
the broadcast server
5 NTP Configuration
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