token ring

Protocol for local area networks, developed by IBM in 1985. A token ring network operates by connecting computers together with copper-based wiring to form a large ring. One or many tokens (sequences of bits) then circulate around the ring continuously. When a computer transmits data it grabs a passing token and attaches the data and the destination address behind the token. The token then continues to circulate around the ring. Every computer on the ring checks every passing token to see if any attached data is addressed to it. When a computer finds a token with data addressed to it, it copies the data, and sets a special bit in the token to say that the data has been received successfully. When the token works its way back around the ring to the originating computer, the originator removes the data and frees up the token for use again. Token ring has been largely superseded by Ethernet as a LAN protocol.