Much like Token Ring, FDDI also employs token passing as its way to get data onto the network. When a station has the token it can transmit data, and once it receives the original data transmission sent, it releases the token onto the network again. The maximum data frame size on a FDDI network is 4500 bytes.
Depending on the type of fiber optic cabling in use, FDDI networks can span distances of 2-30 kilometers between devices. The maximum number of attached stations on a FDDI network is 500.
The equipment found on a FDDI network is unique when compared to Token Ring or Ethernet. Firstly, FDDI utilizes two rings, each of which passes data in a different direction (referred to as counter-rotating rings). The purpose of the two rings is to provide fault tolerance. When operating normally, one ring is active, and the other on standby. In cases where a cable breaks, the ring is wrapped on both sides of the failure to allow continued operation.
