ProNET 10 Token recovery

ProNET 10 token recovery is essential to handle situations of loss of token when the host want to transmit. Such token loses occur due to malfunction or electronic interference that damages the token. To recover the token, we implement two timers at each station – flag timers and token timers. The flag timer is reset whenever the station detects an activity i.e. a frame or token. The token timer is reset when the token arrives. Now, if both the timers have expired, waiting for a longtime to reset (i.e facing non availability of token), the station changes to recovery mode and this generates a new token for the ring.

If the ring is completely idle, the flag timer will expire waiting for 3ms and to support large packet transmission upto 255 stations, the token timer should allow higher expiration time ~ 400ms. If two stations try to transmit the frames and newly generated token simultaneously after a token loss, then problem arises since both the stations will not be able to receive back their transmission. When such a situation arises, both the stations shall back off for a random time and then starts transmitting so that the collision is avoided. The random time for wait is determined as a function of their hardware address so that on the second time, the network is completely recovered.

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