Madge Networks 802.11b Manuel d'utilisateur télécharger pdf (Page 6)

IEEE 802.5/IBM Token Ring

• The stations form a logical ring (star-wired-ring network)

– Small frame (token) circulates when idle

– Only the possession of a token allows a node to transmit

– Upon possession, a sending station changes one bit in token to

make it SOF for data frame

– Appends rest of data frame to the token

– Frame makes round trip, reaches destination and is finally

absorbed by transmitting station

• sending station can perform some checks to see if frame was

received correctly by the destination node

– Sending station then inserts new token when transmission has

finished and leading edge of returning frame arrives

– Token rings give deterministic access and delay is deterministic

• They are used in applications where predictable delay and

robustness of network is needed

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Madge Networks 802.11b Manuel d'utilisateur Page 6