Huawei Quidway S5600 Series - Page 832

Operation Manual – NTP
Quidway S5600 Series Ethernet Switches-Release 1510 Chapter 1 NTP Configuration
Huawei Technologies Proprietary
1-3
Netw ork
Netw ork
NTP Pac ket 10:00:00am
Netw ork
Netw ork
11:00:01am
10:00:00am 11:00:01am 11:00:02am
10:00:00am
NTP Packet received at 10:00:03
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Pac ket 10:00:00 am
Netw ork
Netw ork
11:00:01 am
10:00:00 am 11:00:01 am 11:00:02 am
10:00:00 am
NTP Packet received at 10:00:03 am
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Pac ket 10:00:00am
Netw ork
Netw ork
11:00:01am
10:00:00am 11:00:01am 11:00:02am
10:00:00am
NTP Packet received at 10:00:03
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Packet 10:00:00 am
Netw ork
Netw ork
11:00:01 am
10:00:00 am 11:00:01 am 11:00:02 am
10:00:00 am
NTP Packet received at 10:00:03 am
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Pac ket 10:00:00am
Netw ork
Netw ork
11:00:01am
10:00:00am 11:00:01am 11:00:02am
10:00:00am
NTP Packet received at 10:00:03
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Pac ket 10:00:00 am
Netw ork
Netw ork
11:00:01 am
10:00:00 am 11:00:01 am 11:00:02 am
10:00:00 am
NTP Packet received at 10:00:03 am
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Pac ket 10:00:00am
Netw ork
Netw ork
11:00:01am
10:00:00am 11:00:01am 11:00:02am
10:00:00am
NTP Packet received at 10:00:03
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Netw ork
Netw ork
NTP Packet 10:00:00 am
Netw ork
Netw ork
11:00:01 am
10:00:00 am 11:00:01 am 11:00:02 am
10:00:00 am
NTP Packet received at 10:00:03 am
1.
2.
3.
4.
LS_A
LS_A
LS_A
LS_A
LS_B
LS_B
LS_B
LS_B
NT P Pac ket
NT P Pac ket
Figure 1-1 Working principle of NTP
The procedures of synchronizing system clocks are as follows:
z LS_A sends an NTP packet to LS_B, with the timestamp identifying the time
when it is sent (that is, 10:00:00am, noted as T
1
) carried.
z When the packet arrives at LS_B, LS_B inserts its own timestamp, which
identifies 11:00:01am (noted as T
2
) into the packet.
z Before this NTP packet leaves LS_B, LS_B inserts its own timestamp once again,
which identifies 11:00:02am (noted as T
3
).
z When receiving the response packet, LS_A inserts a new timestamp, which
identifies 10:00:03am (noted as T
4
), into it.
At this time, LS_A has enough information to calculate the following two parameters:
z The delay for an NTP packet to make a round trip between LS_A and LS_B:
delay = (T
4
-T
1
)-(T
3
-T
2
).
z The time offset of LS_A with regard to LS_B: offset = ((T
2
-T
1
) + (T
3
-T
4
))/2.
LS_A can then set its own clock according to the above information to synchronize its
clock to that of LS_B.
For the detailed information, refer to RFC1305.