FDDI Framing

A FDDI data frame is comprised of nine different fields, including a preamble that marks the beginning of a frame. FDDI actually makes use of an encoding scheme that translates groups of 4 bits into 5-bit symbols, referred to as 4B/5B. These symbols are used to represent control, error, and data information. FDDI frames include the following fields:

Start Delimiter. Indicates the beginning of a frame.
Frame Control. Used to determine whether the frame is a token or data frame.
Destination Address. The destination MAC address for the frame.
Source Address. The source MAC address for the frame.
Data. The data encapsulated by upper-layer protocols.
Frame Check Sequence. Contains the CRC value for the frame.
End Delimiter. Used to indicate the end of a frame.
Frame Status. Field used by the source station to ensure that the data was received at the destination.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of 2000Trainers.com. He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.