3Com CoreBuilder 3500, Руководство по внедрению

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Key Concepts 99
SMT has six key frame-based protocols:
■
Neighbor Notification
— Allows SMT to learn the addresses of the
logical neighbors of each MAC in a station. This information is useful
in detecting and isolating network faults.
■
Parameter Management — Performs the remote management of
station attributes. It operates on all SMT MIB attributes, attribute
groups, and actions.
■
Status Reporting — Allows a station to notify network managers
about events such as station configuration changes and network
errors.
■
Status Polling — Provides a mechanism to obtain station status
remotely through a request/response protocol.
■
Echo — Performs loopback testing on the FDDI dual ring.
■
Synchronous Bandwidth Allocation — Allocates synchronous
bandwidth and monitors both synchronous and total bandwidth.
Primary and
Secondary Paths
FDDI’s dual, counter-rotating ring is made up of a primary and secondary
ring. You can be connect FDDI stations to either ring or to both rings
simultaneously. Data flows downstream on the primary ring in one
direction from one station to its neighboring station. The secondary ring
serves as a redundant path and flows in the opposite direction. When a
link or station failure occurs, the ring
wraps around the location of the
failure, creating a single logical ring.
Paths represent the segments of a logical ring that pass through a station.
An FDDI station can contain two paths:
■
Primary path — The segment or segments of the primary ring that
pass through a station. Conditions may exist in parts of the network
that cause the path to be in a different ring. The primary path must be
present in all nodes on the network.
■
Secondary path — The segment or segments of the secondary ring
that pass through a station. Conditions may exist in parts of the
network that may cause the path to be in a different ring.
Media Access Control The Media Access Control (MAC) uses a token-passing protocol to
determine which station has control of the physical medium (the ring).
The MAC delivers frames to their destinations by scheduling and
performing all data transfers.