Physical Topology: A Ring Of Trees - 3Com LANPLEX 2500 Operation Manual

FDDI Network Topologies 10-3
Physical Topology: The FDDI trunk ring consists of dual-attach stations (DASs) and dual-attach
A Ring of Trees connectors (DACs). The DACs on the ring allow you to attach trees. The trees
consist of branches of single-attach stations (SASs) and DASs that are
star-wired off the concentrators. There are several advantages to creating
this kind of network. In addition to being highly reliable, the ring of trees
provides a single, fault-tolerant ring, offers fault isolation, and allows
centralized management. See Figure 10-3.
Duplex link
FDDI trunk ring
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ring of trees
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Figure 10-3 Ring of Trees
All physical connections in an FDDI topology are duplex links (a pair of
insulated fiber optic conductors). Both the FDDI trunk ring and the ring of
trees created through concentrators are made up of duplex links. The nodes
in an FDDI network must be interconnected to form at most one trunk ring.
If a topology is legal, when physical connections and nodes fail or are
removed from the network, one or more legal FDDI topologies are formed.