Quick Tech Tip - FDDI - Fiber distributed data interface

Fiber distributed data interface (FDDI) provides a standard for data transmission in a local area network that can extend in range up to 200 kilometers (124 miles). FDDI is a token-passing, fiber ring, network. The fiber optic media can be multimode fiber and can be as large as 100 kilometers - with no more than 2 kilometers between nodes.

Why FDDI?
- More Powerful Workstations and Servers.
- Resource Intensive Network Applications.
- Growing Distributed Client/Server Applications.
- Larger Spans of Distributed Networks.
- Increasing Numbers of Network Users.
- Bigger and More Powerful Software Applications.

FDDI Benefits:
- Higher Capacity and Performance than older LANs.
- More Simultaneous Transactions.
- Higher Availability (dual ring topology).
- Predetermined Performance (adding users have minimal impact on throughput).
- Longer Distance Loops (2 kilometers to 100 kilometer).

FDDI uses dual-ring architecture with traffic on each ring flowing in opposite directions (called counter-rotating). The dual rings consist of a primary and a secondary ring. During normal operation, the primary ring is used for data transmission, and the secondary ring remains idle.

FDDI specifies the physical and media-access portions of the OSI reference model. FDDI is not actually a single specification, but it is a collection of four separate specifications, each with a specific function. Combined, these specifications have the capability to provide high-speed connectivity between upper-layer protocols such as TCP/IP and IPX, and media such as fiber-optic cabling.