Installing and Administering HP FDDI/9000 Software

Chapter 1 25

FDDI Resources

FDDI Concepts

Figure 1-2 FDDI Network Map

During normal operation, the two rings in an FDDI network are

independent and the primary ring, represented by the solid line, actively

transmits data in accordance with a timed-token protocol. The secondary

ring, represented by the dotted line, remains inactive, providing a

redundant LAN capability, until a fault occurs to break the primary ring.

In the example above, the mainframe, concentrator and router are

connected to both the primary and secondary rings simultaneously via A

and B port types. These stations can access either or both rings for data

transmission and can reconﬁgure the network, if necessary. Stations

directly connected to the dual ﬁber optic ring are referred to as

dual-attached stations (DAS) or dual-attached concentrators

(DAC). HP FDDI/9000 supports dual attach and dual homing

capabilities on Series 800 systems.

FDDI Network

Model 735 Workstation

Concentrator

Router

Concentrator

Mainframe

FDDI Dual Fibre

Model 755 Workstation

Series 800 System

Optic Ring

Ethernet

IEEE 802.3

Printer

A, B, M and S = Port Types

Dual Attach

S800

System