Installing and Administering HP EISA FDDI/9000 and HP HSC FDDI/9000

22 Chapter 1
HP FDDI/9000 Resources
FDDI Concepts
• Single Attachment Station (SAS): Connects only to the primary ring.
Generally, a SAS connects to the FDDI ring through a DAC.
Network designers and administrators are given the opportunity to
balance the costs of installation and operation with the quality of service
demanded by each segment. For example, a dual set of fiber running
between stations is much more expensive than connecting the stations
with a single fiber. Thus, a dual ring topology is typically used for major
backbones in the system. Single rings are generally used to branch off
the backbones to various workgroups and peripheral installations
NOTE DAC and DAS connect directly to the FDDI dual ring while SAC and
SAS only connect to a single, primary ring.
Dual attachment does not provide greater performance than single
attachment. It only provides a secondary means of communication in
case of failure on the primary ring.
ANSI FDDI Standards
Figure 1-2 shows the four ANSI FDDI standards and how they combine
to form a completely functional fiber optic network. This figure also
shows how these standards fit into the OSI model.