Huawei AR150 Series Configuration Manual page 100

Huawei AR150&200&1200&2200&3200 Series Enterprise
Routers
Configuration Guide - Device Management
Figure 5-3 Unicast Client/Server Mode
Perform clock filtering and
c l o c k s e l e c t i o n , a n d
synchronize its clock to that of
the preferred server
During and after the restart, the host operating in client mode periodically sends NTP request
messages to the host operating in server mode. After receiving the NTP request message, the
server swaps the position of destination IP address and source IP address, and the source port
number and destination port number, fills in the necessary information, and sends the message
to the client. The server does not need to retain state information when the client sends the request
message. The client freely adjusts the interval for sending NTP request messages according to
the local conditions.
Peer Mode
The peer mode runs on a lower stratum on a synchronous subnet. In this mode, a active peer and
a passive peer can synchronize with each other. The peer with a higher stratum (a lower level)
synchronizes with a peer with a lower stratum (a higher level).
In peer mode, the active peer initiates an NTP packet with the Mode field set to 3 (the client
mode), and the passive peer responds with an NTP packet with the Mode field set to 4 (the server
mode). This interaction creates a network delay so that devices at both ends enter the peer mode.
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Issue 05 (2014-01-16)
Client
Active peer: A host that functions as a active peer sends packets periodically. The value of
the Mode field in a packet is set to 1. This indicates that the packet is sent by a active peer,
without considering whether its peer is reachable and which stratum its peer is on. The
active peer can provide time information about the local clock for its peer, or synchronize
the time information about the local clock based on that of the peer clock.
Passive peer: A host that functions as a passive peer receives packets from the active peer
and sends reply packets. The value of the Mode field in a reply packet is set to 2. This
indicates that the packer is sent by a passive peer. The passive peer can provide time
information about the local clock for its peer, or synchronize the time information about
the local clock based on that of the peer clock.
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C l o c k s y n c h r o n i z a t i o n p a c k e t s
（mode3）
Reply packets（mode4）
5 NTP Configuration
Server
Automatically run in server
mode, and send reply packets
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