Manualsbrain.com
  1. 매뉴얼
  2. 브랜드
  3. 3com
  4. 8807
  5. 사용자 가이드

3com 8807 사용자 가이드

다운로드
페이지 중 883
754
C
HAPTER
 66: NTP C
ONFIGURATION
Figure 176   Basic operating principle of NTP
In the figure above, Switch A and Switch B are connected through the Ethernet 
port. They have independent system clocks. Before implement automatic clock 
synchronization on both switches, we assume that:
■
Before synchronizing the system clocks on Switch A and B, the clock on Switch 
A is set to 10:00:00am, and that on B is set to 11:00:00am.
■
Switch B serves as an NTP time server. That is, Switch A synchronizes the local 
clock with the clock of B.
■
It takes one second to transmit a data packet from either A or B to the opposite 
end.
The system clocks are synchronized as follows:
■
Switch A sends an NTP packet to Switch B. The packet carries the timestamp 
10:00:00am (T
1
) that tells when it left Switch A.
■
When the NTP packet arrives at Switch B, Switch B adds a local timestamp 
11:00:01am (T
2
) to it.
■
When the NTP packet leaves Switch B, Switch B adds another local timestamp 
11:00:02am (T
3
) to it.
■
When Switch A receives the acknowledgement packet, it adds a new 
timestamp 10:00:03am (T
4
) to it.
Now, Switch A collects enough information to calculate the following two 
important parameters:
NTP packet
10:00:00AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP packet
10:00:00AM
11:00:01AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP packet
10:00:00AM
11:00:01AM
11:00:02AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP Packet received at 10:00:03
1.
2.
3.
4.
NTP
10:00:00AM
NTP
10:00:00AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
11:00:02AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP Packet received at 10:00:03
1.
2.
3.
4.
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
11:00:02AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP Packet received at 10:00:03
1.
2.
3.
4.
NTP packet
10:00:00AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP packet
10:00:00AM
11:00:01AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP packet
10:00:00AM
11:00:01AM
11:00:02AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP Packet received at 10:00:03
1.
2.
3.
4.
NTP
10:00:00AM
NTP
10:00:00AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
11:00:02AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP Packet received at 10:00:03
1.
2.
3.
4.
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP
10:00:00AM
11:00:01AM
11:00:02AM
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NETWORK
LS_A
LS_B
NETWORK
NETWORK
LS_A
LS_B
----------------------------------------------------------------
---------------------------------------
NTP Packet received at 10:00:03
1.
2.
3.
4.