Sun Microsystems 1.0 - Manual (Page 83)

FDDI Network Architecture 57
6
Dual-Attached Station (DAS)
A dual-attached station (DAS) is attached to the FDDI network through two
connectors called the A-port and the B-port, respectively. The A-port has a
primary input (Pin) and a secondary output (Sout); the B-port has a primary
output (
Pout ) and a secondary input (Sin).
The primary input/output is attached to the primary ring and the secondary
input/output is attached to the secondary ring. The flow of data during
normal operation is shown in Figure 6-5.
To complete the ring, you must ensure that the B-port of an upstream station is
always connected to the A-port of a downstream station. For this reason, most
FDDI DAS connectors are keyed to prevent connections between two ports of
the same type.
Figure 6-5 Dual-Attached Station (DAS)
Dual-attached station
(DAS)
P in P out
Data from upstream station Data to downstream station
MAC
PHY B PHY A
S in
Data from downstream station
S out
Data to upstream station
B-port A-port