Ntp Supported By The S9300&S9300E - Huawei S9300 Configuration Manual

S9300&S9300E Terabit Routing Switch
Configuration Guide - Network Management
4.
4.2 NTP Supported by the S9300&S9300E
This part describes NTP operating modes supported by the S9300&S9300E.
The switch supports the following NTP working modes
l
l
l
l
l
Unicast Client/Server Mode
In this mode, you need to configure only the client. The server needs to be configured with only
one NTP primary clock.
Note that the client can be synchronized to the server but the server cannot be synchronized to
the client.
After the configuration, the following actions occur:
1.
2.
3.
Peer Mode
In this mode, you need to configure NTP only on the symmetric active end. The symmetric active
end and symmetric passive end can be synchronized with each other.
Note that the clock with a lower stratum is synchronized to the one with a higher stratum.
Issue 01 (2012-03-15)
When Switch A receives the response packet, it adds a new receiving timestamp to it, which
is 10:00:03 am (T4).
Switch A uses the received information to calculate the following two important values:
l Delay for the NTP message cycle: Delay = (T4 - T1) - (T3 - T2).
l Offset of Switch A relative to Switch B: Offset = ((T2 - T1) + (T3 - T4))/2.
According to the delay and the offset, Switch A sets its own clock again to synchronize
with the clock of Switch B.
The preceding example is only a simple description of the NTP operating principle. As
described in RFC 1305, NTP uses a complex algorithm to ensure the precision of clock
synchronization.
The server and client are two relative concepts. The device that provides standard time is
referred to as a time server, and the device that enjoys the time service is referred to as a
client.
Unicast Client/Server Mode
Peer Mode
Broadcast Mode
Multicast Mode
Manycast Mode
The client sends a synchronization request packet to the server, with the mode field being
set to 3. The value 3 indicates the client mode.
Upon receiving the request packet, the server automatically works in the server mode and
sends a response packet with the mode field being set to 4. The value 4 indicates the server
mode.
After receiving the response packet, the client performs clock filtering and selection, and
finally, is synchronized with the optimal server.
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4 NTP Configuration
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