Token-passing meaning

A communications network access method that uses a continuously repeating frame (the token) that is transmitted onto the network by the controlling computer. When a terminal or computer wants to send a message, it waits for an empty token that it fills with the address of the destination station and some or all of its message.Every node on the network constantly monitors the passing tokens to determine if it is a recipient of a message, in which case it "grabs" the message and resets the token status to empty. Token passing uses bus and ring topologies. See token bus network and token ring network.
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A deterministic, i.e., noncontentious, access method used in Token-Passing Ring,Token Ring, and Token Bus local area networks (LANs).The token, which consists of a specific bit pattern, indicates the status of the network -- available or unavailable. The token is generated by a centralized master control station and transmitted across the network. The station in possession of the token controls the access to the network. That station may either transmit or require other stations to respond. Transmission is in the form of a data packet of a predetermined maximum size, determined by the number of nodes on the ring and the traffic to be supported; oversized transmissions are segmented, or fragmented. After transmitting, the station passes the token to a successor station, in a predetermined sequence.While the process is complex and overhead-intensive, its high level of control over the network avoids data collisions and increases throughput. See also deterministic, LAN, node, packet, throughput, token, and Token Ring.
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