Introduction to Data Communications
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45b. IEEE 802.4 Token Bus

An industrial version of Token Ring is standardized under IEEE 802.4 Token Bus. It is used in manufacturing process equipment for plant operation. It is used in automobile plants for computerized assembly. It uses a Logical Ring and a Physical Bus topology.

45c. IEEE 802.5 Token Ring

IEEE 802.5 Token Ring standard is based on the IBM Token Ring network. Token Ring has been used mainly in large corporations and was considered in the past to be the only way to handle data communications in large networks (1000+) nodes.

Token Ring equipment is more expensive than Ethernet and is one of the reasons that Ethernet is more popular. The other reason is that Token Ring is much more complex bus arbitration method than CSMA/CD and few network personnel understand the full capabilities of Token Ring.

45d. IEEE 802.5 Bus Arbitration

Token Ring is a token passing bus arbitration. A token is circulated on the ring. If a node on the ring needs to access the ring (transfer information), it claims the token.

Introduction to Data Communications
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