Dual-attached station (das) – Sun Microsystems 1.0 User Manual
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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