H3C Technologies H3C SecPath F1000-E - Manual (Page 119)

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NOTE:
•
A CE is a device that has an interface directly connecting to the service provider (SP). A CE is not
“aware of” the presence of the VPN.
• A PE is a device directly connecting to CEs. In an MPLS network, all events related to VPN
processing occur on the PE.
NTP Configuration Task List
Complete the following tasks to configure NTP:
Task Remarks
Configuring the Operation Modes of NTP Required
Configuring the Local Clock as a Reference Source Optional
Configuring Optional Parameters of NTP Optional
Configuring Access-Control Rights Optional
Configuring NTP Authentication Optional
Configuring the Operation Modes of NTP
Devices can implement clock synchronization in one of the following modes:
• Client/server mode
• Symmetric mode
• Broadcast mode
• Multicast mode
For the client/server mode or symmetric mode, you need to configure only clients or symmetric-active
peers; for the broadcast or multicast mode, you need to configure both servers and clients.
NOTE:
A single device can have a maximum of 128 associations at the same time, including static associations
and dynamic associations.
• A static association refers to an association that a user has manually created by using an NTP
command.
• A dynamic association is a temporary association created by the system during operation. A dynamic
association is removed if the system fails to receive messages from it over a specific long time.
In client/server mode, for example, when you execute a command to synchronize the time to a server, the
system creates a static association, and the server just responds passively upon the receipt of a message,
rather than creating an association (static or dynamic). In symmetric mode, static associations are created
at the symmetric-active peer side, and dynamic associations are created at the symmetric-passive peer
side. In broadcast or multicast mode, static associations are created at the server side, and dynamic
associations are created at the client side.