Token-Ring Lan Technology was developed by IBM in the middle 1980s as a fast and reliable alternative to Ethernet. Token ring technology uses a different concept, known as token passing, for allowing network adapters to transmit data on the media. Token Ring uses a star ring topology, a hybrid topology, looking physically like a star but logically wired as a ring.
Token-Ring operates in a logical ring, where the central device which is used to connect the network devices (Servers, Workstations, Printers, Scanners etc.) hosts an internal ring, where access to the network media for a network device is given only by the possession of a token that is passed from device to device on the ring. The central device which is used to connect the network devices is called as a Multistation Access Unit, or MAU. Please click the link to view an image of IBM token ring MAU.
Token-Ring is more sophisticated than Ethernet, and it includes a number of built-in diagnosis and correction mechanisms that can help troubleshoot network problems and Token-Ring networks does not produce the collisions that can take place in the Ethernet Network.
When a Token-Ring network starts up, the devices take part in a negotiation to decide who will become the "Active Monitor". In Token-Ring network, "Active Monitor" is a machine with the highest MAC address and all other machines are 'Standby Monitors'. The job of the Active Monitor is to make sure that none of the machines are causing problems on the network, and to re-establish the ring after a break or an error has occurred.
A computer that passes the token to the next computer on the logical ring would be called the nearest active upstream neighbor (NAUN). The computer receiving the token is the nearest active downstream neighbor (NADN). Once a computer takes possession of the token and transmits data, it then creates a new token and passes it to its NADN.
Early Token-Ring networks had 4Mbps speed and later 16Mbps and 100Mbps speed Token-Ring networks were also available. Token Ring networks are fast replaced by Ethernet family technologies due to the advantages of Ethernet technologies.
• Network Access Methods - CSMA/CD, CSMA/CA and Token Passing
• LAN Technologies - Ethernet
• Ethernet Media Standards
• Lan Technologies - Fibre Distributed Data Interface (FDDI)
• IEEE 802 Standards