
Configuring Line Services
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Figure 2-6. Failure of Node on Ring
FDDI Ring Operation
An FDDI ring consists of nodes in a ring architecture. There are two classes of
nodes: stations (a node with no master ports), and concentrators (a node with
master ports).
The FDDI standards define two types of stations: single attachment stations (SAS)
and dual attachment stations (DAS). The SAS connects to only one ring; it cannot
wrap the ring in case of a fault. The DAS connects to both the primary and
secondary rings. The Bay Networks router is an example of a DAS.
FDDI initializes the ring and transmits data as follows:
1. The nodes on the ring establish connections with their neighbors.
The Connection Management (CMT) portion of SMT controls this process, as
described in “FDDI SMT,” later in this chapter.
2. The nodes negotiate the target token rotation time (TTRT), using the claim
token process.
Primary ring wraps
to secondary ring,
isolating faulty node.
LS0008A
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