Cabletron Systems STHI manual Hub-By-Hub Bypass Control, Automatic Beacon Recovery Process

STHI Overview

1.2.4Hub-By-Hub Bypass Control

Unless otherwise configured by a user, all hubs in an STH/STHI stack are interconnected to form a continuous Token Ring. Through Local Management, however, each hub may be individually bypassed from the continuous ring to form its own isolated ring which does not exchange data with the other hubs.

If an STH is bypassed from the main ring, the STH module will not receive data-dependent services such as statistical tracking and beacon recovery, but other physical control functions such as port configuration remain unaffected. If the STHI is bypassed, only its TCUs are actually bypassed from the stack’s common ring: TPIM Ring ports and management systems maintain their connection to the stack’s common ring.

Refer to Section 5.6.2, Multiplexer Configuration Fields, for instructions regarding bypass control.

1.2.5Automatic Beacon Recovery Process

To guard the network against operational interruptions due to beaconing conditions, the STHI protects itself and its attached STH hubs with Cabletron Systems’ advanced Automatic Beacon Recovery Process. ABRP engages more quickly and is able to treat conditions beyond the scope of the IEEE standard beacon recovery process. The STHI automatically partitions problematic lobes from the ring, allowing the rest of the ring to continue operating. The hub checks partitioned Ring In/Out ports periodically and re-enables them automatically if they have recovered; partitioned TCU ports remain disabled until re-enabled by a user.

1.2.6Support for Passive MAU Workgroups

By default, each TCU port is configured to its STN (station) setting to support lobe connections to stations. Whereas a station signals a TCU to open its interface by providing phantom current down its lobe cable, a passive Multi-Station Access Unit cannot provide phantom current. To allow for MAU connections, the user may reconfigure TCU ports via Local Management to function in Ring Out mode. A TCU port in Ring Out mode looks for the presence of data bits, rather than phantom current, to determine link status. Refer to Section 5.6.3, Port Configuration Fields, Subsection RING OUT ENABLE Mode, for configuration instructions.

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