Operation Modes Of Ntp - 3Com MSR 50 Series Configuration Manual

Operation Modes of NTP

Receive Timestamp: the local time at which the request arrived at the service
■
host.
Transmit Timestamp: the local time at which the reply departed the service host
■
for the client.
Authenticator: authentication information.
■
Devices running NTP can implement clock synchronization in one of the following
modes:
Server/client mode
Figure 612 Server/client mode
Performs clock filtering and
selection, and synchronizes its local
clock to that of the optimal reference
source
When working in the server/client mode, a client sends a clock synchronization
message to servers, with the Mode field in the message set to 3 (client mode).
Upon receiving the message, the servers automatically work in the server mode
and send a reply, with the Mode field in the messages set to 4 (server mode). Upon
receiving the replies from the servers, the client performs clock filtering and
selection, and synchronizes its local clock to that of the optimal reference source.
In this mode, a client can be synchronized to a server, but not vice versa.
Symmetric peers mode
Figure 613 Symmetric peers mode
Symmetric active
The symmetric peers mode is
established and the two devices
can synchronize, or be
synchronized by each other
A device working in the symmetric active mode periodically sends clock
synchronization messages, with the Mode field in the message set to 1 (symmetric
Client
Network
Clock
synchronization
message
Reply
peer
Network
Clock synchronization message
exchange (Mode 3 and Mode 4)
Clock
synchronization
message
Reply (Mode 2)
Synchronize
each other
NTP Overview
Server
Automatically works
in server /client
(Mode 3)
mode and sends a
reply
(Mode 4)
Symmetric
passive peer
Automatically
works in
(Mode 1)
symmetric
peers mode
and sends a
reply
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