Token Ring: Mutual Exclusion in Distributed Systems

08 Apr 2011 by

Token Ring Mutex

Token Ring Mutex

Token ring is one among mutual exclusion algorithm in distributed systems that does not involve with a server or coordinator. A token is passed from one node to another node in a logical order. A node received token has a proper right to enter the critical section. If a node being holding token does not require to enter critical section or access a shared resource, it just simply passes the token to the next node.

Advantages and Disadvantages

Advantages

  • Process suffer from no starvation. Before entering a critical section, a process waits at most for the duration that all other processes enter and exit the critical section
  • No hand sake messages are required to get the token. Then less overhead

 

Disadvantages

  • If a token is lost for some reasons, another token must be regenerated
  • Detecting lost token is difficult since there is no upper bound in the time a token takes to rotate the ring (no particular timeout)
  • The ring must be reconstructed when a process crashes

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