HP 200 Series Services And Applications page 236

Shining a Light on FDDI
Technology Overview
Technology Overview
Fiber Distributed Data Interface (FDDI) is an ANSI and ISO specification
(X3T9) for the transmission of data at high speeds, typically 100 Mbit/s,
using fiber-optic cable as the transmission medium. Optical fiber technology
offers networks a great degree of flexibility in bandwidth and topology
design. Fiber-optic cable also offers excellent noise immunity, and is
virtually impossible to tap.
FDDI is a token-passing technology that uses a timed-token protocol to
guarantee network access between network stations (network devices and
end nodes). Figure 1 shows a standard dual-attached ring. Network access is
negotiated between stations at initialization and at every time a new node is
added to the network.
R
Dual Counter-Rotating
FDDI Ring
R
Figure 1. FDDI Ring
The network backbone is constructed of stations interconnected by two
counter-rotating rings. These rings are two pairs of fiber-optic cable to which
each device is attached. Cable lengths between stations can be anywhere
from 2 kilometers (km) with multimode fiber, to 60 km with single-mode
fiber. The total ring length cannot exceed a maximum of 200 km. During
normal operation, the first ring is the primary data carrier, and the second
acts as the backup. This offers the network a greater degree of redundancy
and fault tolerance.
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