Fddi and Cddi
C H A P T E R
8
Chapter Goals
• • • •
Provide background information about FDDI technology. Explain how FDDI works. Describe the differences between FDDI and Copper Distributed Data Interface (CDDI). Describe how CDDI works.
Fiber Distributed Data Interface
Introduction
The Fiber Distributed Data Interface (FDDI) specifies a 100-Mbps token-passing, dual-ring LAN using fiber-optic cable. FDDI is frequently used as high-speed backbone technology because of its support for high bandwidth and greater distances than copper. It should be noted that relatively recently, a related copper specification, called Copper Distributed Data Interface (CDDI), has emerged to provide 100-Mbps service over copper. CDDI is the implementation of FDDI protocols over twisted-pair copper wire. This chapter focuses mainly on FDDI specifications and operations, but it also provides a high-level overview of CDDI. 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. As will be discussed in detail later in this chapter, the primary purpose of the dual rings is to provide superior reliability and robustness. Figure 8-1 shows the counter-rotating primary and secondary FDDI rings.
Internetworking Technologies Handbook 1-58705-001-3
8-1
Chapter 8 FDDI Transmission Media
Fiber Distributed Data Interface
Figure 8-1
FDDI Uses Counter-Rotating Primary and Secondary Rings
Primary
Secondary FDDI
Concentrator
WAN
Standards
FDDI was developed by the American National Standards Institute (ANSI) X3T9.5 standards committee in the mid-1980s. At the time, high-speed engineering workstations were beginning to tax the bandwidth of existing local-area networks (LANs) based on Ethernet and Token Ring. A new LAN media was needed that could easily support these workstations
8
Chapter Goals
• • • •
Provide background information about FDDI technology. Explain how FDDI works. Describe the differences between FDDI and Copper Distributed Data Interface (CDDI). Describe how CDDI works.
Fiber Distributed Data Interface
Introduction
The Fiber Distributed Data Interface (FDDI) specifies a 100-Mbps token-passing, dual-ring LAN using fiber-optic cable. FDDI is frequently used as high-speed backbone technology because of its support for high bandwidth and greater distances than copper. It should be noted that relatively recently, a related copper specification, called Copper Distributed Data Interface (CDDI), has emerged to provide 100-Mbps service over copper. CDDI is the implementation of FDDI protocols over twisted-pair copper wire. This chapter focuses mainly on FDDI specifications and operations, but it also provides a high-level overview of CDDI. 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. As will be discussed in detail later in this chapter, the primary purpose of the dual rings is to provide superior reliability and robustness. Figure 8-1 shows the counter-rotating primary and secondary FDDI rings.
Internetworking Technologies Handbook 1-58705-001-3
8-1
Chapter 8 FDDI Transmission Media
Fiber Distributed Data Interface
Figure 8-1
FDDI Uses Counter-Rotating Primary and Secondary Rings
Primary
Secondary FDDI
Concentrator
WAN
Standards
FDDI was developed by the American National Standards Institute (ANSI) X3T9.5 standards committee in the mid-1980s. At the time, high-speed engineering workstations were beginning to tax the bandwidth of existing local-area networks (LANs) based on Ethernet and Token Ring. A new LAN media was needed that could easily support these workstations