FDDI

The American National Standards Institute (ANSI) developed the Fiber Distributed Data Interface (FDDI) standard in the mid-1980s to meet the growing need for a reliable and fast networking system to accommodate distributed applications. FDDI uses a ring network design, but, unlike the traditional 802.5 standard, FDDI uses a dual ring technology for fault tolerance. Because of the dual ring design, FDDI is not susceptible to a single cable failure like the regular 802.5 IEEE standard. Figure 1.8 shows an FDDI network with a dual ring configuration.

Figure 1.8. FDDI network.

As with any of the other standards, FDDI has specific characteristics:

Speed FDDI transmits data at 100Mbps and higher.
Topology FDDI uses a dual ring topology for fault-tolerant reasons.
Media FDDI uses fiber-optic cable that enables data transmissions that exceed two kilometers. Additionally, it is possible to use FDDI protocols over copper wire known as the Copper Distributed Data Interface (CDDI).
Access method Similar to 802.5, FDDI uses a token-passing access method.

Table 1.7 summarizes each of the wired standards discussed in the previous sections.

Table 1.7. IEEE 802 Network Standards
Standard	Speed	Physical Topology	Logical Topology	Media	Access Method
802.3	10Mbps		Bus and Star	Coaxial and twisted pair	CSMA/CD
802.3u	100Mbps (Fast Ethernet)	Star	Bus	Twisted pair	CSMA/CD
802.3z	1000Mbps	Star	Bus	Twisted pair	CSMA/CD
802.3ae	10-Gigabit		Backbone connections	N/A	Fiber/Not Required
802.5	4Mbps and 16Mbps	Star	Ring	Twisted pair	Token passing
FDDI	100Mbps	Dual ring	Ring	Fiber-optic Twisted pair (CDDI).	Token passing

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