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G. Bauer, T. Frenning, A.K. Jonsson, H. Kopetz, C. Temple:
"A Centralized Approach for Avoiding the Babbling-Idiot Failure in the time-Triggered Architecture";
Vortrag: ICDSN, New York, USA; 01.06.2000; in: "Proceedings of the ICDSN 2000", (2000), S. #.

A babbling-idiot - a node that transmits at random instants for an arbitrary duration - is one of the most serious failures in a distributed system, where nodes communicate by means of a multiaccess broadcast network. This is because a single babbling-idiot has the capability of preventing correct nodes from successfully exchanging messages.
In the "Time-Triggered Architecture" the communications media is arbitrated using a time-division multiple access (TDMA) scheme, a time multiplexing strategy with a statically scheduled periodic media access pattern. Since in TDMA based communication it is known a-priori when a subscriber is granted access to the communication media it is possible to build a supervisor unit preventing subscribers from sending messages outside of their assigned time slots, thus guarding against babbling-idiots.

In "Avoiding the babbling-idiot failure in a time-triggered communication system" an approach to build such a supervisor is presented: it is based on the idea to equip every subscriber with an independent additional unit - the bus guardian - that grants bus access to the respective subscriber during its assigned time slots.

However, when the physical network topology is changed from a bus topology to a star topology (which in some sense is only a very short bus) it is reasonable to introduce a central bus guardian that acts as a supervisor for all of the subscriber nodes at the star point of the network.

In the following we want to present the basic functionality of such a central bus guardian and discuss some of the properties that are related with this type of supervisor unit.

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