Fiber Distributed Data Interface (FDDI)

FDDI is an American National Standards Institute (ANSI) topology standard that uses fiber-optic cable and token-passing media access.

FDDI is implemented using both multimode and single-mode fiber cable and can reach transmissions speeds of up to 100Mbps at distances of more than 2 kilometers. FDDI combines the strengths of Token Ring, the speed of Fast Ethernet, and the security of fiber-optic cable. Such advantages make FDDI a strong candidate for creating network backbones and connecting private LANs to create MANs and WANs.

Unlike the regular 802.5 network standard, FDDI uses a dual-ring configuration. The first, or primary, ring is used to transfer the data around the network, and the secondary ring is used for redundancy and fault tolerance; the secondary ring waits to take over if the primary ring fails. If the primary ring fails, the secondary ring kicks in automatically, with no disruption to network users.

FDDI has a few significant advantagessome of which stem directly from the fact that it uses fiber-optic cable as its transmission media. These include a resistance to EMI, the security offered by fiber, and the longer distances available with fiber cable. In addition to the advantages provided by the fiber-optic cable, FDDI itself has a few strong points, including

  • Fault-tolerant design By using a dual-ring configuration, FDDI provides some fault tolerance. If one cable fails, the other can be used to transmit the data throughout the network.

  • Speed because of the use of multiple tokens Unlike the IEEE 802.5 standard, FDDI uses multiple tokens, which increase the overall network speed.

  • Beaconing FDDI uses beaconing as a built-in error-detection method, making finding faults, such as cable breaks, a lot easier.

Like every technology, there are always a few caveats:

  • High cost The costs associated with FDDI and the devices and cable needed to implement an FDDI solution are very costly; too costly for many small organizations.

  • Implementation difficulty FDDI setup and management can be very complex, requiring trained professionals with significant experience to manage and maintain the cable and infrastructure.