Huawei AR150 Series Configuration Manual page 101

Huawei AR150&200&1200&2200&3200 Series Enterprise
Routers
Configuration Guide - Device Management
Figure 5-4 Peer mode
The symmetric peer mode
being established, and the
two can synchronize clocks
with each other
NOTE
The passive peer does not need to be configured. A host sets up a connection and sets relevant state variables
only when it receives an NTP packet.
Broadcast Mode
The broadcast mode is applied to the high speed network that has multiple workstations and
does not require high accuracy. In a typical scenario, one or more clock servers on the network
periodically send broadcast packets to the workstations. The delay of packet transmission in a
LAN is at the milliseconds level.
l
Broadcast server: A host that runs in broadcast mode sends clock synchronization packets
to the broadcast address 255.255.255.255 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 broadcast mode,
without considering whether its peer is reachable and which stratum its peer is on. The host
running in broadcast 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.
l Broadcast client: The client listens to the clock synchronization packets sent from the
server. When the client receives the first clock synchronization 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 broadcast mode, and continues to sense the incoming clock
synchronization packets to synchronize the local clock.
Issue 05 (2014-01-16)
Symmetric active peer
Interaction of clock synchronization
packets (mode3 and mode4)
Clock synchronization packets
(mode1)
Reply packets (mode2)
Synchronize clocks with each other
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5 NTP Configuration
Symmetric passive peer
Automatically work in symmetric
p e e r m o d e , a n d s e n d r e p l y
packets
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