Token bus is a network implementing a
Token Ring
Token Ring network
IBM hermaphroditic connector with locking clip. Screen contacts are prominently visible, gold-plated signal contacts less so.
Token Ring is a computer networking technology used to build local area networks. It was introduc ...
protocol over a ''virtual ring'' on a
coaxial cable. A token is passed around the network nodes and only the node possessing the token may transmit. If a node doesn't have anything to send, the token is passed on to the next node on the virtual ring. Each node must know the address of its neighbour in the ring, so a special protocol is needed to notify the other nodes of connections to, and disconnections from, the ring.
Ethernet's access protocol could not absolutely guarantee a maximum time any station would have to wait to access the network, so was thought to be unsuitable for manufacturing automation applications. The Token bus protocol was created to combine the benefits of a physical bus network with the deterministic access protocol of a Token Ring network.
Token bus was standardized by IEEE standard 802.4. It was mainly used for industrial applications. Token bus was used by
General Motors for their
Manufacturing Automation Protocol (MAP) standardization effort. This is an application of the concepts used in
Token Ring
Token Ring network
IBM hermaphroditic connector with locking clip. Screen contacts are prominently visible, gold-plated signal contacts less so.
Token Ring is a computer networking technology used to build local area networks. It was introduc ...
networks. The main difference is that the endpoints of the bus do not meet to form a physical ring.
In order to guarantee the packet delay and transmission in Token bus protocol, a modified Token bus was proposed in Manufacturing Automation Systems and
flexible manufacturing system
A flexible manufacturing system (FMS) is a manufacturing system in which there is some amount of flexibility that allows the system to react in case of changes, whether predicted or unpredicted.
This flexibility is generally considered to fall ...
(FMS).
A means for carrying
Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
...
over
IEEE 802
IEEE 802 is a family of Institute of Electrical and Electronics Engineers (IEEE) standards for local area networks (LAN), personal area network (PAN), and metropolitan area networks (MAN). The IEEE 802 LAN/MAN Standards Committee (LMSC) mainta ...
networks, including token bus networks, was developed.
The IEEE 802.4 Working Group has disbanded and the standard has been withdrawn by the IEEE.
See also
*
ARCNET
Attached Resource Computer NETwork (ARCNET or ARCnet) is a communications protocol for local area networks. ARCNET was the first widely available networking system for microcomputers; it became popular in the 1980s for office automation tasks. It ...
*
Network topology
Network topology is the arrangement of the elements ( links, nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and contr ...
References
{{DEFAULTSORT:Token Bus Network
Local area networks
IEEE 802
Link protocols