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Fiber distributed data interface (FDDI) provides a standard for data transmission
Data transmission

Data transmission is the physical transfer of data from point-to-point often represented as an electro-magnetic Signal over a point-to-point or point-to-multipoint communication channel....
 in a local area network
Local area network

A local area network is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport....
 that can extend in range up to 200 kilometers (124 miles). Although FDDI protocol is a token ring network, it does not use the IEEE 802.5 token ring protocol
Communications protocol

In the field of telecommunications, a communications protocol is the set of standard rules for data representation, Signalling , authentication and Error detection and correction required to send information over a communications channel....
 as its basis; instead, its protocol is derived from the IEEE 802.4 token bus
Token bus

Token bus is a network implementing the token ring 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....
 timed token protocol. In addition to covering large geographical areas, FDDI local area networks can support thousands of users.






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Fiber distributed data interface (FDDI) provides a standard for data transmission
Data transmission

Data transmission is the physical transfer of data from point-to-point often represented as an electro-magnetic Signal over a point-to-point or point-to-multipoint communication channel....
 in a local area network
Local area network

A local area network is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport....
 that can extend in range up to 200 kilometers (124 miles). Although FDDI protocol is a token ring network, it does not use the IEEE 802.5 token ring protocol
Communications protocol

In the field of telecommunications, a communications protocol is the set of standard rules for data representation, Signalling , authentication and Error detection and correction required to send information over a communications channel....
 as its basis; instead, its protocol is derived from the IEEE 802.4 token bus
Token bus

Token bus is a network implementing the token ring 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....
 timed token protocol. In addition to covering large geographical areas, FDDI local area networks can support thousands of users. As a standard underlying medium it uses optical fiber
Optical fiber

An optical fiber is a glass or plastic fiber that carries light along its length. Fiber optics is the overlap of applied science and engineering concerned with the design and application of optical fibers....
 (though it can use copper
Copper

Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity....
 cable, in which case one can refer to CDDI
CDDI

CDDI is a customary name for FDDI copper twisted pair physical medium dependent specification, described in ANSI X3.263-1995 ....
). FDDI uses a dual-attached, counter-rotating token ring topology.

FDDI, as a product of American National Standards Institute
American National Standards Institute

The American National Standards Institute or ANSI is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States....
 X3T9.5 (now X3T12), conforms to the Open Systems Interconnection
OSI model

The Open Systems Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection initiative....
 (OSI) model of functional layering of LANs using other protocols. FDDI-II, a version of FDDI, adds the capability to add circuit-switched service
Circuit switching

In telecommunications, a circuit switching network is one that establishes a telecommunication circuit between Node and Terminal before the user may communicate, as if the nodes were physically connected with an electrical circuit....
 to the network so that it can also handle voice and video
Video

Video is the technology of electronics Videography, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing Scene in motion....
 signals. Work has started to connect FDDI networks to the developing Synchronous Optical Network
Synchronous optical networking

Synchronous optical networking and Synchronous Digital Hierarchy , are two closely related multiplexing protocols for transferring multiple digital bit streams using lasers or light-emitting diodes over the same optical fiber....
 SONET.

A FDDI network contains two token rings, one for possible backup in case the primary ring fails. The primary ring offers up to 100 Mbit/s capacity. When a network has no requirement for the secondary ring to do backup, it can also carry data, extending capacity to 200 Mbit/s. The single ring can extend the maximum distance; a dual ring can extend 100 km (62 miles). FDDI has a larger maximum-frame size than standard 100 Mbit/s Ethernet
Ethernet

Ethernet is a family of Data frame-based computer networking technologies for local area networks . The name comes from the physical concept of the Luminiferous aether....
, allowing better throughput.

Designers normally construct FDDI rings in the form of a "dual ring of trees" (see network topology
Network topology

Network topology is the study of the arrangement or mapping of the elements of a Computer networking, especially the physical and logical interconnections between nodes....
). A small number of devices (typically infrastructure devices such as router
Router

A router is a Computer network device whose software and hardware are usually tailored to the tasks of routing and forwarding information. For example, on the Internet, information is directed to various paths by routers....
s and concentrators rather than host computers) connect to both rings - hence the term "dual-attached". Host computers then connect as single-attached devices to the routers or concentrators. The dual ring in its most degenerate form simply collapses into a single device. Typically, a computer-room contains the whole dual ring, although some implementations have deployed FDDI as a Metropolitan area network
Metropolitan area network

Metropolitan area networks, or MANs, are large computer networks usually spanning a city. They typically use wireless infrastructure or Optical fiber connections to link their sites....
.

FDDI requires this network topology because the dual ring actually passes through each connected device and requires each such device to remain continuously operational (the standard actually allows for optical bypasses, but network engineers consider these unreliable and error-prone). Devices such as workstations and minicomputers that might not come under the control of the network managers are not suitable for connection to the dual ring.

As an alternative to using a dual-attached connection, a workstation can obtain the same degree of resilience
Resilience (network)

In computer networking: ?Resilience is the ability to provide and maintain an acceptable level of Service in the face of Fault and challenges to normal operation.?...
 through a dual-homed connection made simultaneously to two separate devices in the same FDDI ring. One of the connections becomes active while the other one is automatically blocked. If the first connection fails, the backup link takes over with no perceptible delay.

Due to their speed, cost and ubiquity, fast Ethernet
Fast Ethernet

In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s....
 and (since 1998) Gigabit Ethernet
Gigabit Ethernet

Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a Data rate units#gigabit_per_second, as defined by the IEEE 802.3-2005 standard....
 have largely made FDDI redundant.

FDDI standards include:
  • ANSI X3.166-1989, Physical Medium Dependent (PMD) -- also ISO 9314-3
  • ANSI X3.148-1988, Physical Layer Protocol (PHY) -- also ISO 9314-1
  • ANSI X3.139-1987, Media Access Control (MAC) -- also ISO 9314-2
  • ANSI X3.229-1994, Station Management (SMT) -- also ISO 9314-6
  • ANSI X3.184-1993, Single Mode Fiber Physical Medium Dependent (SMF-PMD) -- also ISO 9314-4


Source: from Federal Standard 1037C
Federal Standard 1037C

Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended....
 and used with permission from http://www.Foldoc.org

See also

  • List of device bandwidths
    List of device bandwidths

    This is a list of device bandwidths: the net bit rate of some computer devices employing methods of data transport is quantified in units of kilobits per second , megabits per second , or gigabits per second as appropriate....