token ring

token ring

A computer local area network arbitration scheme in whichconflicts in the transmission of messages are avoided by thegranting of "tokens" which give permission to send. A stationkeeps the token while transmitting a message, if it has amessage to transmit, and then passes it on to the nextstation.

Often, "Token Ring" is used to refer to the IEEE 802.5 tokenring standard, which is the most common type of token ring.

Usenet newsgroup: news:comp.dcom.lans.token-ring.

Token Ring

An earlier local area network (LAN) access method developed by IBM. Conforming to the IEEE 802.5 standard, the Token Ring access method connects up to 255 nodes in a star topology at 4, 16 or 100 Mbps. All stations connect to a central wiring hub called the "Multistation Access Unit" (MAU) using twisted wire cable. Today, most Token Ring business networks have migrated to Ethernet.

Different than Ethernet
The Token Ring MAU may be a central hub, but it does not function like a shared Ethernet hub. Token Ring is more deterministic, which ensures that all users get regular turns at transmitting. With Ethernet, all users compete to get onto the network.

Type 1 and Type 3
Type 1 Token Rings allow up to 255 stations per network and use shielded twisted pair wires with IBM style Type 1 connectors. Type 3 allows up to 72 devices per network and uses unshielded twisted pair (Cat 3, 4 or 5) with RJ-45 connectors. Like Ethernet, Token Ring is a data link protocol and functions at layers 1 and 2 of the OSI model. See token passing, data link protocol and OSI model.

Token Ring Topology
Token Ring uses a logical ring topology, which provides more equal opportunity for each station to gain access to the network than the broadcast method used by Ethernet. All nodes connect to the MAU.