R3204P16-HP Load Balancing Module System Management Configuration Guide-6PW101

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broadcast messages from servers. When a client receives the first broadcast message, the client and the
server start to exchange messages with the Mode field set to 3 (client mode) and 4 (server mode), to
calculate the network delay between client and the server. Then, the client enters broadcast client mode.
The client continues listening to broadcast messages, and synchronizes its local clock based on the
received broadcast messages.
Multicast mode
Figure 58 Multicast mode
In multicast mode, a server periodically sends clock synchronization messages to the user-configured
multicast address, or, if no multicast address is configured, to the default NTP multicast address 224.0.1.1,
with the Mode field in the messages set to 5 (multicast mode). Clients listen to the multicast messages
from servers. When a client receives the first multicast message, the client and the server start to
exchange messages with the Mode field set to 3 (client mode) and 4 (server mode), to calculate the
network delay between client and server. Then, the client enters multicast client mode. It continues
listening to multicast messages, and synchronizes its local clock based on the received multicast
messages.
NOTE:
In symmetric peers mode, broadcast mode and multicast mode, the client (or the symmetric active peer)
and the server (the symmetric passive peer) can work in the specified NTP workin
g
mode only after the
y
exchange NTP messages with the Mode field being 3 (client mode) and the Mode field being 4 (server
mode). During this message exchange process, NTP clock synchronization can be implemented.
Multiple Instances of NTP
When operating in client/server mode or symmetric mode, NTP supports multiple instances of NTP, and
thus realizes clock synchronization within an MPLS VPN network. In other words, the clock of network
devices (CEs and PEs) at different physical location can be synchronized through NTP, as long as they are
in the same VPN. The following functions are available:
• An NTP client on a customer edge device (CE) can be synchronized to an NTP server on another
CE.
• An NTP client on a CE can be synchronized to an NTP server on a provider edge device (PE).
• An NTP client on a PE can be synchronized to an NTP server on a CE through a designated VPN
instance.
• An NTP client on a PE can be synchronized to an NTP server on another PE through a designated
VPN instance.
Network
ClientServer
After receiving the first
multicast message, the
client sends a request
Clock synchronization message
exchange (Mode 3 and Mode 4)
Periodically multicasts clock
synchronization messages (Mode 5)
Calculates the network delay
between client and the server
and enters the multicast
client mode
Periodically multicasts clock
synchronization messages (Mode 5)
Receives multicast
messages and synchronizes
its local clock