TOKEN RING  Token Ring was developed by several manufacturers and it copes well with high network traffic loadings, and were at one time extremely popular. The Ethernet has since overtaken their popularity. An electronic token (named a control token) is circulates around a closed electronic loop (network) . Each node on the network reads the token and repeats it to the next node. The control token circulates around the ring even when there is no data being transmitted. If a nodes on the network wishing to transmit it must await for a token. When the node gets a token, it fill a frame with data and add the source and destination addresses then send it to the next node. The data frame then circulates around the ring until it reaches the destination node. The destination node then reads the data into its local memory area (or buffer) and marks an acknowledgement on the data frame. This then circulates back to the source (or originating) node. When the original node receives the frame, it tests it to determine whether it contains an acknowledgement. If it does then the source node knows that the data frame was received correctly. If the source node has finished transmitting data then it transmits a new token, which can be used by other nodes on the ring. Using the diagram below, a control token as in (a)  circulates between all the nodes. This token does not contain any data and is only a few bytes long. If node B  receives the token it then transmits a data frame, as illustrated in (b). This data frame is passed to node C, then to node D and finally onto A. Node A then reads the data in the data frame and returns an acknowledgement to node B, as in (c). After node B receives the acknowledgement, it passes a control token onto node C and this then circulates until a node wishes to transmit a data frame. In Token Ring no nodes are allowed to transmit data unless they have received a valid control token. The sequence in which nodes transmit is determined by a distributed control protocol thus giving each node equal access to the ring, as each node is only allowed to send one data frame ( exception  FDDI - allow for a time limit on transmitting data, before the token is released). After transmision of a data frame  node must give up the token to the next node, and wait for the token to return before it can transmit another data frame. Example of data Exchange  Token Ring maintenance  A Token Ring system requires considerable maintenance; it must perform the following functions:  Ring initialisation - when the network is started, or after the ring has been broken, it must be reinitialised. A co-operative decentralized algorithm sorts out which node starts a new token, which goes next, and so on. Adding to the ring - if a new node is to be physically connected to the ring then the network must be shut down and reinitialised. Deletion from the ring - a node can disconnect itself from the ring by joining together its Predecessor and its successor. Again, the network may have to be shut down and reinitialised. Fault management - typical Token Ring errors occur when two nodes think it is their turn to transmit or when the ring is broken as no node thinks that it is their turn. Token Ring multistation access units (MAUs) MAU reduces significantly the problems of adding and deleting nodes to or from a ring network.  top Links               Token Ring/IEEE 802.5   Token Ring and IEEE 802.5 support two basic frame types:  NETWORK TECHNOLOGIES   Token Ring/IEEE 802.5 (PDF)  Frame Format. Token Ring and IEEE 802.5 support two basic frame types. Token Ring   The token ring topology uses a logical ring. Token Ring & FDDI (PDF)  MultiStation Access Units (MSAU) in central locations ie not in individual  Linux on Token Ring LG #47   MSAU (multistation access unit)  iCom   Protocol that provides a way to perform primitive maintenance operations  Network+   Hubs Repeaters and Multistation Access Units. Media Attachment Units and Transceivers. ... Token Ring Frame Format. ... Security, Maintenance and Support, Network Security.  Local Area Networks   Multistation access units (MSAUs). COMMUNICATIONS & NETWORKING   MAU (Multistation Access Unit). Central point for network cables. ... High installation cost. Maintenance and repairs are difficult. ... Requires a bus topology. Token Ring. ... Networking Terms   RTMP - Routing table maintenance protocol is used to .. TLD - Top Level domain; Token Ring - A network architecture developed by IBM which sends tokens around a ..   Topics               TOKEN RING   Network Topologies   MAC   Upgrading and Repairing Networks   Books             systems integration(amazon.com) Distributed systems and Networks(amazon.com) "Understanding Token Ring Protocols and Standards" by James T. Carlo, et.al. (amazon.com)   Home News Topics Resources Jobs About Us Designed by Nwanganga, Chukwuemeka C.	Related Topics LAN components Cabling standards Token Ring/IEEE 802.5     more Topics
	Related Links ONline Token Ring Media Module Installation Guide (PDF)  MAC Media Access Control. Lower of the two sublayers of the data ... more links
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