HP Certified: HP-UX System Administration

The FDDI networks use a dual ring topology with a token passing access method. One of these rings is the primary ring and the other one is the secondary. Two rings are used to provide redundancy so that the network does not fail in case of the failure of one ring. Fiber optic cable is used for interconnection. FDDI networks operate at 100 Mbits per second speed. An FDDI network may be visualized as shown in Figure 27-8.

Single and dual attachment stations (SAS and DAS) are used with an FDDI network. A single attachment station is attached to one ring, while a dual attachment station is attached to both rings. The dual attachment stations are also used to automatically reconfigure the ring in case of cable failure.