Fiber Distributed Data Interface (FDDI) - Tutorial

Welcome to the Network Engineer training section of CoreNetworkZ Tech Solutions. Today, I am discussing a popular fiber optic connections network standard, FDDI.

FDDI stands for Fiber Distributed Data Interface (FDDI), a Local Area Network standard. Today, we check the data transfer speed, maximum distance it supports, different versions, working principle, and the specifications of this network standard.

Krishna Ravi, a B.Tech student, asked, "I heard ISPs are using FDDI standards. Can you tell me why?"

He asked this question in our support forum. Some technicians also asked me why the FDDI was popular with ISPs.

The truth is that ISPs are no longer using the FDDI standard. But, it was popular once because it supported high bandwidth and security.

Aditi Gupta, a System Admin trainee at CoreNetworkZ Tech Solutions, said, "I read communication through FDDI offers high security. Why is that?"

I will answer Aditi's question here.

Communication through this standard is very secure due to its dual-ring structure. As you understand, the FDDI standard uses the primary ring for communication. It supports up to 100 Mbps in standard case.

The second token ring is for possible backup ( in case of the failure of the primary ring). If the second ring is also used to carry data, the total speed will increase up to 200 Mbps.

Now, let us check the different versions of this data communication standard.

Muneesh Ali Muhammad, a regular reader of CoreNetworkZ Tech Solutions, asked, "Hello Alex, I am preparing for CCNA. According to the exam syllabus, I should learn about various types of FDDI. Can you explain them?"

He asked this question in our support forum. Let me share two popular versions here.

1. FDDI-II

   This version is suitable for transmitting video, with voice, over a network. FDDI-2 supports the transmission of voice and video information as well as data. This version adds the capability to add circuit-switched service to the network.

2. FDDI Full Duplex Technology (FFDT)

   It uses the same network infrastructure but can potentially support data rates up to 200 Mbps. So, this standard can offer the data transfer rate of an ordinary FDDI network where both Token Rings transfer data.

Rony Mathew, a Software Engineer from Bengaluru, said, "One of my projects needs apps based on FDDI standard. However, after reading the FDDI documentation, I have more doubts. Can you explain the working of the Fiber Distributed Data Interface standard? Please note that I am not from a Network Engineer background."

Many beginners find the workings of FDDI confusing. So, read this part carefully.

FDDI uses a dual-ring architecture with traffic on each ring flowing in opposite directions. If the data transfer in ring 1 is in the clockwise direction, the second ring sends data in an anticlockwise direction.

Fiber Distributed Data Interface is treated as highly secure because of its dual-ring character. FDDI uses optical fiber as the primary transmission medium, but it also can run over copper cabling.

A few readers of CoreNetworkZ Tech Solutions asked me about different FDDI specifications.

FDDI is a collection of four specifications, each with a specific function. The function of the multi-specification is to provide high-speed connectivity between upper-layer protocols.

1. Physical Layer Protocol (PHY)
   
   
2. Physical-Medium Dependent (PMD)
   
   
3. Media Access Control (MAC)
   
   
4. Station Management (SMT)

To read more about the FDDI specification, visit this link.

Hemanth Reddy, a Computer Science and Engineering student from Vijayawada, said, "I read the documentation, and the FDDI technology is awesome. I wonder why no one is using this technology anymore."

The answer to his question is simple. We have better technologies now. FDDI is costly and obsolete. I believe you found this article helpful. Feel free to share your comments about FDDI below.

1. https://www.ibm.com/docs/en/aix/7.2.0?topic=control-data-link-fddi-dlc-fddi-overview
2. https://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1905.pdf
3. https://answers.microsoft.com/en-us/windows/forum/all/fddi-network-card-where-to-download-the-driver/9c578ffd-7995-44e5-84a8-b7f2848e1e6c
4. https://www.juniper.net/documentation/en_US/junos/topics/concept/fddi-overview.html