3Com LANPLEX 2500, Руководство по эксплуатации

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9-6 C
HAPTER
9: FDDI O
VERVIEW AND
I
MPLEMENTATION
PHY/PMD entities (M ports) are used for connecting other FDDI stations,
including other concentrators, in a tree topology.
Attachments Attachments refer to how a node, station, or concentrator is connected to
an FDDI network. They are classified as
single attachment and dual
attachment. Concentrators can be classified as null attachment when the A
and B ports are either not present or not used.
■
Single attachment — A station or concentrator that has only one
physical connection to an FDDI network. The single attachment cannot
accommodate a dual (counter-rotating) ring. A single attachment station or
concentrator has
an S port that attaches to an M port within a concentrator tree.
■
Dual attachment — Any station or concentrator that has two physical con-
nections to an FDDI network. This type of attachment can accommodate a
dual (counter-rotating) ring. A dual attachment station has one A-B port
pair; a dual attachment concentrator has an A-B port pair and at least one
M port.
■
Null attachment — Concentrators that have one or more M ports but no
A, B, or S ports.
Node Types Six station and concentrator types are used to describe station
configurations and topologies. Figure 9-1 lists these node types and their
abbreviations. Figure 9-2 shows how these six node types may connect to
an FDDI dual ring.
The LANplex® 2500 system only supports SM-DAS and SAS topologies.
.
Table 9-1 Node Types and Abbreviations
Node Type Abbreviation
Single MAC-Dual Attachment Station SM-DAS
Dual MAC-Dual Attachment Station DM-DAS
Single Attachment Station SAS
Dual Attachment Concentrator DAC
Single Attachment Concentrator SAC
Null Attachment Concentrator NAC