Introduction to NTP
293
At this time, LS_A has enough information to calculate the following two parameters:
■
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
).
■
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.
NTP Implementation
Mode
To accommodate networks of different structures and switches in different network
positions, NTP can operate in multiple modes, as described in the following.
Client/Server mode
Figure 90
NTP implementation mode: client/Sever mode
Peer mode
Figure 91
NTP implementation mode: peer mode
In peer mode, the active peer sends clock synchronization packets first, and its peer
works as a passive peer automatically.
If both of the peers have reference clocks, the one with smaller stratum is adopted.
Netw ork
Client
Server
Clock synchronization
request packet
Response packet
Filter and select clocks
and synchronize its
ow n clock to that of
the selected server
Work as a server
automatically and
send response
packets
Netw ork
Client
Server
Response packet
Filter and select clocks
and synchronize its
ow n clock to that of
the selected server
Work as a server
automatically and
send response
packets
Netw ork
Client
Server
Clock synchronization
request packet
Response packet
Filter and select clocks
and synchronize its
ow n clock to that of
the selected server
Work as a server
automatically and
send response
packets
Netw ork
Client
Server
Response packet
Filter and select clocks
and synchronize its
ow n clock to that of
the selected server
Work as a server
automatically and
send response
packets
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
In peer mode, both
sides are synchronized
to the clock w ith
smaller stratum
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
Active peer
Passive peer
Netw ork
Clock synchronization
request packet
Operates in the passive
peer mode automatically
Netw ork
Response packet
Synchronize
In peer mode, both
sides are synchronized
to the clock w ith
smaller stratum
Summary of Contents for 4200G 12-Port
Page 10: ...8 CONTENTS...
Page 14: ...4 ABOUT THIS GUIDE...
Page 46: ...32 CHAPTER 5 LOGGING IN THROUGH WEB BASED NETWORK MANAGEMENT SYSTEM...
Page 48: ...34 CHAPTER 6 LOGGING IN THROUGH NMS...
Page 60: ...46 CHAPTER 9 VLAN CONFIGURATION...
Page 64: ...50 CHAPTER 10 MANAGEMENT VLAN CONFIGURATION...
Page 80: ...66 CHAPTER 13 GVRP CONFIGURATION...
Page 98: ...84 CHAPTER 15 LINK AGGREGATION CONFIGURATION...
Page 112: ...98 CHAPTER 18 MAC ADDRESS TABLE MANAGEMENT...
Page 126: ...112 CHAPTER 19 LOGGING IN THROUGH TELNET...
Page 162: ...148 CHAPTER 20 MSTP CONFIGURATION...
Page 274: ...260 CHAPTER 29 IGMP SNOOPING CONFIGURATION...
Page 276: ...262 CHAPTER 30 ROUTING PORT JOIN TO MULTICAST GROUP CONFIGURATION...
Page 298: ...284 CHAPTER 33 SNMP CONFIGURATION...
Page 304: ...290 CHAPTER 34 RMON CONFIGURATION...
Page 338: ...324 CHAPTER 36 SSH TERMINAL SERVICES...
Page 356: ...342 CHAPTER 38 FTP AND TFTP CONFIGURATION...
Page 365: ...Information Center Configuration Example 351 S4200G terminal logging...
Page 366: ...352 CHAPTER 39 INFORMATION CENTER...
Page 378: ...364 CHAPTER 40 BOOTROM AND HOST SOFTWARE LOADING...
Page 384: ...370 CHAPTER 41 Basic System Configuration and Debugging...
Page 388: ...374 CHAPTER 43 NETWORK CONNECTIVITY TEST...
Page 406: ...392 CHAPTER 45 CONFIGURATION OF NEWLY ADDED CLUSTER FUNCTIONS...