Describe any one method of Logical Clock synchronization with the help of an example.

Q.Describe any one method of Logical Clock synchronization with the help of an example. (December 2018 ) (10 Marks)

Ans- The concept of time in distributed systems is used to order events. The assumption is that the execution of a process is characterized by a sequence of events. An event can be the execution at one instruction or of one procedure or sending a message or receiving a message. Under some condition it is possible to ascertain the order of the events logical clocks try to catch this.

 

Logical clocks :

The happened before relation ( →) is defined as follows :

• A→B if A & B are within the same process & A occurred before B.
• A→B if A is an event at sending messages in one process end B is the event of receiving M in another process. 
• A→B and B→C then A→C
  Event A causally affects event B if A→Bdistinct events A & B are ( A || B) if we do not have A→B or B→A
  

Example: