PCI FDDI Administrator's Guide

PCI FDDI
PCI FDDI Devices
Chapter 1 23
PCI FDDI Devices
To promote ease of installation and maintenance, PCI FDDI allows for
several types of networking devices. These include dual ring and single
ring concentrators and stations. Concentrators are the building blocks of
a PCI FDDI network. Stations and concentrators connect to the PCI
FDDI ring as follows:
• Dual Attachment Concentrators (DAC): Connects to the dual
ring and serves as a hub for single or dual attachment devices. It also
allows stations to be added and removed from the ring with minimal
interruption of network traffic.
• Single Attachment Concentrator (SAC): Connects to the primary
ring through a DAC and serves as a single ring hub. SACs can be
stacked to form a span of trees topology.
• Dual Attachment Station (DAS): Connects to a dual ring. Both
primary and secondary paths are connected.
• Single Attachment Station (SAS): Connects only to the primary
ring. Generally, a SAS connects to the PCI 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 backbone to various workgroups and peripheral installations.
DAC and DAS connect directly to the PCI 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 a failure on the primary ring.