Introduction to Data Communications
Previous	45m. Token Ring Monitors and Servers (cont'd)	Next

There is only 1 Active Monitor allowed on the ring at a time, all other stations become Standby Monitors. Standby Monitors determine whether the Active Monitor is functioning properly. If a Standby Monitor determines that the Active Monitor is not operating properly, the Standby Monitor initiates the Token Claiming process.

Duties of the Standby Monitor

a. The Standby Monitor checks to see if a Token is circulating the ring. It has a Timer called the "Good_token" timer and knows that a Token has to circulate within that time. If the Token does not go by within this designated period, the Standby Monitor knows that Active Monitor is not doing its job. The Standby Monitor then initiates the Token Claiming process to re-elect an Active Monitor.

b. The Standby Monitor restarts another Timer called "receive notification" whenever an Active Monitor Present frame comes by. If the Timer runs out before another Active Monitor Present frame arrives, the SM assumes that the Active Monitor is not present or has malfunctioned. The SM initiates the Token Claiming process to re-elect an Active Monitor.

Introduction to Data Communications
Previous	Table of Contents	Next