This section takes a look at FDDI as a technology which builds on the foundations set by Token Ring and introduces many new concepts that make this technology both more sophisticated and flexible than either Token Ring or Ethernet. The approach taken is to provide a general overview in this chapter, and then build up the detail on a layer by layer basis, in relation to layers within the OSI Model, in subsequent chapters. By starting at the Physical Layer and building through the MAC Layer, and then finishing by taking a look at the management functions that help control the whole operation, it is hoped that a thorough understanding can be gained in a step by step fashion.