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FDDI Network Architecture 59
6
Dual-Attached Concentrator (DAC)
A dual-attached concentrator (DAC) is attached to the FDDI network through
two ports—the A-port and the B-port, which are identical to the ports on a
dual-attached station. It has multiple M-ports, to which single-attached
stations are connected, as shown in Figure 6-7.
Dual-attached concentrators and FDDI stations are often arranged in a very
flexible network topology called the ring of trees. This configuration is
discussed in more detail in Chapter 7, “FDDI Network Topologies.”
Figure 6-7 Dual-Attached Concentrator (DAC)
Single-attached station
(SAS)
Dual-attached
concentrator
(SAC)
S-port
Single-attached station
(SAS)
S-port
Pin
Pout
Data from upstream station
Data to downstream station
Sin
Data from upstream station
Sout
Data to downstream station
A-port
B-port
M-port M-port
Single-attached station
(SAS)
S-port
M-port