Jain, R., "Token Ring Network Having Token Request Mechanism,"Patent No. 5,053,946, Issued October 01, 1991, Filed May 07, 1990, Assigned to Digital Equipment Corporation.


A token ring network includes a plurality of stations interconnected to transmit frames containing information. A station may originate a frame transmission if it has information to transmit and if it is holding a token. A frame includes the information and a token request flag initialized to a selected condition. While one station is originating transmission of the frame around the network, if another station needs to transmit a frame, that station conditions the token request flag to another predetermined condition. The originating station receives the frame and examines the token request flag. If the token request flag has the predetermined condition, it transmits the token over the network to permit another station to originate a frame transmission. Thus, unless another station needs to transmit a frame, as indicated to the originating station by the condition of the token request flag, the originating station may continue to transmit, and so the time an originating station may transmit is not limited to any arbitrary time period.

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