FDDI: Advantages and Disadvantages

This article explores the benefits and drawbacks of FDDI (Fiber Distributed Data Interface).

What is FDDI? (Introduction)

FDDI stands for Fiber Distributed Data Interface. Here’s a breakdown:

• It’s essentially a high-performance fiber optic token ring network.
• Think of it as similar to 802.5 and IBM token rings, but it uses fiber optic cables instead of copper.
• It can support up to 1000 connections.
• It covers a total fiber length of up to 200 Km.
• It boasts a data transmission rate of approximately 100 Mbps.
• It utilizes multimode optical fiber with the following specifications:
  • Optical source: 1300 nm LED
  • Core diameter: 62.5 micron
  • Cladding diameter: 125 micron
  • Numerical aperture: 0.275
  • Bandwidth: 500 MHz/Km

• The 4B5B line code is used for data encoding.
• Frame sizes range from 17 to 4500 bytes.
• FDDI cabling consists of two fiber rings: a primary and a secondary ring. One transmits clockwise, and the other transmits counter-clockwise.
• FDDI defines two traffic classes: synchronous and asynchronous.

Benefits or Advantages of FDDI

Here are the key advantages of using FDDI:

• Higher Bandwidth: Offers bandwidth up to 250 Gbps, handling data rates up to 100 Mbps.
• High Security: Fiber optic links are difficult to eavesdrop on, enhancing security.
• Durability: Fiber optic cables are less prone to breakage compared to other cable types.
• Immunity to EMI: Fiber optic cables are not affected by Electromagnetic Interference (EMI).
• Long-Distance Transmission: Fiber optic cables can transmit signals over greater distances, up to about 200 Kms.
• Lightweight: Fiber optic cables weigh less than copper wires with similar bandwidth capabilities.
• Multiple Tokens: FDDI uses multiple tokens to improve network speed.
• Priority Handling: It’s possible to prioritize workstations connected in the chain. Some stations can be bypassed to provide faster service to others based on requirements.
• Fault Isolation: FDDI can isolate faulty nodes using wiring concentrators for instantaneous re-routing. Wiring concentrators act as centralized cabling connection devices for workstations.

Drawbacks or Disadvantages of FDDI

Keep these disadvantages in mind when considering FDDI:

• Complexity: FDDI is complex, demanding a high level of expertise for installation and maintenance.
• Cost: FDDI is costly due to the expense of fiber optic cables, adapters, and concentrators.