Fddi fiber distributed data interface
1 / 17

FDDI (Fiber Distributed Data Interface) - PowerPoint PPT Presentation

  • Uploaded on

FDDI (Fiber Distributed Data Interface). Standardized by ASI and ITU-T (ITU-T X.3. FDDI (Fiber Distributed Data Interface). Data rate – 100 Mbps Access method – token passing CDDI – copper version. S-frames – synchronous (real time data) A-frame – asynchronous (not real time).

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' FDDI (Fiber Distributed Data Interface)' - nevan

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Fddi fiber distributed data interface

FDDI (Fiber Distributed Data Interface)

Standardized by ASI and ITU-T (ITU-T X.3

FDDI (Fiber Distributed Data Interface)

Data rate – 100 Mbps

Access method – token passing

CDDI – copper version

S-frames – synchronous (real time data)

A-frame – asynchronous (not real time)

Access method
Access Method


    • Synchronous allocation (SA)

    • Target token rotation time (TTRT)

    • Absolute maximum time (AMT)

  • Access is limited by time

  • Priority – real time data

  • Steps

    • A station captures the token

    • Send S-frames first

    • Any remaining time may then be used to send A-frames

Time registers
Time Registers

Synchronous Allocation (SA)

  • Length of time allowed for S-frames

  • Different for each station

  • Ring initialization

Target Token Rotation Time (TTRT)

  • Average time required for a token to circulate around the ring exactly once

  • Absolute Maximum Time (AMT)

    • Twice the TTRT

    • To avoid monopolizing the network


Token Rotation Timer (TRT)

  • Runs continuously

  • Measures the actual time taken by the token to complete a cycle

  • Incrementing or (decrementing) TRT

Token Holding Timer (THT)

  • Begins running as soon as the token is received

  • Shows how much time remains for sending asynchronous frames

  • Decrementing or (incrementing ) THT

Station procedure
Station Procedure

  • Set the values of timers

    • THT = TTRT – TRT

    • TRT = 0

  • Sends synchronous data

  • Sends asynchronous data as long as the value of THT is positive

Fddi example
FDDI Example


  • TTRT = 30 time units

  • Traveling token from one station to another = 1 time unit

  • Each station is allowed to send 2 S-frames per turn

  • Each station has a lot of A-frames to send

Figure 12-22

FDDI Example

Round 0 – The token travels around the ring: each station sets its TRT timer to 0

FDDI Example

Figure 12-22-continued

FDDI Encoding

Figure 12-23


4b 5b encoding
4B/5B Encoding

None of the five bit patterns start with more than one zero

Transforms each 4-bit data into a 5-bit unit that contains no more than two consecutive 0s

4b 5b encoding1
4B/5B Encoding

Unused five-bit codes are used for control

FDDI Layers

Figure 12-24

Figure 12-25

FDDI Frames

Each frame is preceded by 16 idle symbols (1111), a total of 64 bits

ED – Full byte in token frame, T control code(s)

FS – same to that of token ring

SD – J and K control codes

FC – Identify the frame type

Figure 12-26

Physical Medium Dependent Layer

Dual Ring

– secondary ring make s FDDI self-healing

FDDI Ring Failure

Figure 12-27

FDDI Nodes

Figure 12-28

MIC – Media Interface Connector

Three Types of Nodes

SAS – Single Attachment Station

DAS – Dual Attachment Station

DAC – Dual Attachment Concentrator